diff --git a/doc/AgainstTruth.md b/doc/AgainstTruth.md index d08537a..787b586 100644 --- a/doc/AgainstTruth.md +++ b/doc/AgainstTruth.md @@ -1,5 +1,7 @@ # Against Truth +[Simon Brooke](mailto:simon@journeyman.cc) + > Hey, what IS truth, man? [Beeblebrox, quoted in [Adams, 1978]] *This title is, of course, a respectful nod to Feyerabend's Against Method* @@ -12,6 +14,10 @@ The second part starts with an account of a system built by the author in colla This document deals only with explanation. Issues relating to inference and especially to truth maintenance will undoubtedly be raised as it progresses, but such hares will resolutely not be followed. +## Note on the quality of the text + +Much of this text was written between 1986 and 1988 on Xerox 1108 and 1186 workstations, in their native WYSIWYG document system, and printed as hard copy; and some was written on the very first generation of Apple Macintosh computer, and again printed as hard copy. The text here is the consequence of scanning the hard copy and running optical character recognition on the scans. It isn't perfect. I am proof reading as I go and I hope that it will improve. + ## Contents ### Frontmatter @@ -26,6 +32,12 @@ This document deals only with explanation. Issues relating to inference and esp ### Part Two: Into the wild wood +1. [Arboretum](Arboretum.html) +2. [Conception](Conception.html) +3. [Reimagining](Reimagining.html) +4. [Implementing](Implementing.html) +5. [Experience](Experience.html) + ### Endmatter 1. [Errata](Errata.html) diff --git a/doc/Analysis.md b/doc/Analysis.md index 7a9cdc7..3615cd8 100644 --- a/doc/Analysis.md +++ b/doc/Analysis.md @@ -1,17 +1,14 @@ -1. Analysis +# Analysis - 1. Accounts from the Philosophy of Science +## Accounts from the Philosophy of Science -<Towards another chapter. What l want to do is: , +(Towards another chapter. What l want to do is: , -1\] present the DN account, and it's defenders. - -2\] present the conventional response - -3\] present the radical response - -4\] add some notes of my own, if possible supported by sources, on the -polemic nature of explanation> +1. present the DN account, and it's defenders. +2. present the conventional response +3. present the radical response +4. add some notes of my own, if possible supported by sources, on the +polemic nature of explanation) This section looks at accounts of explanation culled from the Philosophy of Science. My reason for starting with this field of study is that @@ -31,9 +28,9 @@ the philosopher. Where a formal description can be encoded into a computer language in a computationally tractable manner, the computer programme can be used to evaluate how well the description matches the phenomenon described, simply by observing how well the computer models -this phenomenon. +this phenomenon. I shall pursue this argument in the second half of this thesis. -1. 1. Some definitions +### Some definitions In part of the discussion that follows, it will be necessary to use a shorthand to describe some of the different positions that have been @@ -58,7 +55,7 @@ looser, more colloquial sense, to define that group of doctrines there is a real world, and that that real world is accurately reflected in our perceptions. -1. 1. Aristotle to Nagel +### Aristotle to Nagel The Philosophy of Science has had the development of an account of explanation as one of its central projects since Aristotle. Aristotle's @@ -68,13 +65,11 @@ should be constructed as syllogisms or chains of syllogisms, the correct explanation in response to 'How do you know that Socrates is mortal?' would be: -Socrates is a man; + Socrates is a man; + All men are mortal; + Therefore Socrates is mortal. -All men are mortal; - -Therefore Socrates is mortal. - -\[a syllogism of the mood barbara \] +*a syllogism of the mood barbara* This account, which has become known as the 'hypothetico-deductive' or 'deductive-nomological' account of explanation, has effectively been the @@ -91,7 +86,7 @@ not all of the same kind." His four types of explanation are: deductive explanations, probabilistic explanations, functional or teleological explanations, and genetic explanations. -1. 1. 1. Deductive explanations +#### Deductive explanations Nagel's deductive explanations have the formal structure of a deductive argument, rather in the manner of a logical proof. This is essentially @@ -99,65 +94,64 @@ the deductive nomological explanation. In the case of the explanation of singularities, it fits neatly with the Toulmin \[below\] - or indeed the sylogistic - form of argument: data, plus principle, imply conclusion: -"It is evident that at least one of the premises in a deductive -explanation of a singular explicandum must be a universal law..." (page -31) +> "It is evident that at least one of the premises in a deductive explanation of a singular explicandum must be a universal law..." (page 31) -"... a deductive scientific explanation, whose explicandum is the -occurance of some event or the possession of some property by a given -object, must satisfy two logical conditions. The premises must include -at least one universal law, whose inclusion is essential to the -deduction of the explicandum. And the premises must also contain a -suitable number of initial conditions." (page 32) +> "... a deductive scientific explanation, whose explicandum is the +> occurance of some event or the possession of some property by a given +> object, must satisfy two logical conditions. The premises must include +> at least one universal law, whose inclusion is essential to the +> deduction of the explicandum. And the premises must also contain a +> suitable number of initial conditions." (page 32) In the case of the explanation of scientific laws, however: -"...all the premises are universal statements; (and) there is more than -one premise, each of which is essential in the derivation of the -exp1icandum..." (page 34) +> "...all the premises are universal statements; (and) there is more than +> one premise, each of which is essential in the derivation of the +> exp1icandum..." (page 34) -"...at least one of the premises must be 'more general' than the law -being explained." (page 37) +> "...at least one of the premises must be 'more general' than the law +> being explained." (page 37) The notion of 'more general' is discussed at length, and is defined as follows: -"Let L~1~ be a law (or a set of laws and theories constituting some -science such as physics), and let 'P~1~' 'P~2~' . . . , 'P~n~' be a set -of 'primitive' predicates in terms of which the predicates occuring in -L~1~ are in some sense definable. (For the sake of simplicity, and -without any loss of the generality of statement, we shall assume that -the predicates are all adjectives or 'one-place' predicates such as -'rigid' or 'heavy' .... ) Similarly, let 'Q~1~' 'Q~2~' . . . , 'Q~n~' be -the corresponding set of primitives for a law L~2~. Finally, let K be a -class of objects, each of which can be significantly (or meaningfully) -characterised, whether truly or falsely, by the predicates of either set -.... We shall also say that an object in K satisfies a law L -'non-vacuously' only if the object actually possesses the various traits -mentioned in the law and, moreover, the traits do stand to each other in -the relations asserted by the law... +> "Let L~1~ be a law (or a set of laws and theories constituting some +> science such as physics), and let 'P~1~' 'P~2~' . . . , 'P~n~' be a set +> of 'primitive' predicates in terms of which the predicates occuring in +> L~1~ are in some sense definable. (For the sake of simplicity, and +> without any loss of the generality of statement, we shall assume that +> the predicates are all adjectives or 'one-place' predicates such as +> 'rigid' or 'heavy' .... ) Similarly, let 'Q~1~' 'Q~2~' . . . , 'Q~n~' be +> the corresponding set of primitives for a law L~2~. Finally, let K be a +> class of objects, each of which can be significantly (or meaningfully) +> characterised, whether truly or falsely, by the predicates of either set +> .... We shall also say that an object in K satisfies a law L +> 'non-vacuously' only if the object actually possesses the various traits +> mentioned in the law and, moreover, the traits do stand to each other in +> the relations asserted by the law... +> +> We now assume the following conditions: (1) Some (and perhaps all) of +> the predicates in the first set occur in the second, but some predicates +> in the second set do not occur in the first set. (2) Every object in K +> has at least one P-property, that is, a property designated by a +> predicate in the first set. (3) There is a non-empty subclass A of +> objects in K possessing only P-properties. (4) There is a non-empty +> subclass ~~A~~ of objects in K each of which possesses at least one Q- +> property that is not a P-property. .... (5) There is a non-empty (but +> not necessarily proper) subclass B of objects in K each of which +> satisfies L~1~ non-vacuously, and such that some objects in B belong to +> A while others belong to ~~A~~. .... (6) There is a non-empty subclass C +> of objects in A for which L~2~ holds non-vacuously, and such that some +> (and perhaps all) of the objects in C also belong to B ..... When these +> six conditions are fulfilled, L~1~ may be said to be more general in K +> than L~2~." (pp 40- 41). -We now assume the following conditions: (1) Some (and perhaps all) of -the predicates in the first set occur in the second, but some predicates -in the second set do not occur in the first set. (2) Every object in K -has at least one P-property, that is, a property designated by a -predicate in the first set. (3) There is a non-empty subclass A of -objects in K possessing only P-properties. (4) There is a non-empty -subclass ~~A~~ of objects in K each of which possesses at least one Q- -property that is not a P-property. .... (5) There is a non-empty (but -not necessarily proper) subclass B of objects in K each of which -satisfies L~1~ non-vacuously, and such that some objects in B belong to -A while others belong to ~~A~~. .... (6) There is a non-empty subclass C -of objects in A for which L~2~ holds non-vacuously, and such that some -(and perhaps all) of the objects in C also belong to B ..... When these -six conditions are fulfilled, L~1~ may be said to be more general in K -than L~2~." (pp 40- 41). - -\[my transcription differs from the original in. that where Nagel uses a +(my transcription differs from the original in. that where Nagel uses a character formed of an upper case letter A with a bar over it, I have used a struck-through A; and, more significantly, Nagel uses an unbarred A in condition 4. From my understanding of the text I have assumed this -is a misprint, and have substituted an struck-through A\] +is a misprint, and have substituted an struck-through A.) +**TODO** check typography as processed by Markdown! Deductive explanations, as stated above, have the general form of the syllogism Barbara. However, Nagel adds a condition: while all the @@ -175,41 +169,35 @@ explicandum. He observes that the 'universal premises' which are subsumed into 'scientific laws' are true. Instead he suplies the weaker condition that: -"...the explanatory premises be compatible with established empirical -facts and be in addition 'adequately supported' (or 'made probable') by -evidence based on data other than the observational data upon which the -acceptance of the explicandum is based." (p 43) +> "...the explanatory premises be compatible with established empirical +> facts and be in addition 'adequately supported' (or 'made probable') by +> evidence based on data other than the observational data upon which the +> acceptance of the explicandum is based." (p 43) -"In maintaining that the premises in an explanation must be 'better -known' than the explicandum, Aristotle was thus simply making explicit -his conception of science. This conception is true of nothing that can -be identified as part of the asserted content of modern empirical -science," (p 45) +> "In maintaining that the premises in an explanation must be 'better +> known' than the explicandum, Aristotle was thus simply making explicit +> his conception of science. This conception is true of nothing that can +> be identified as part of the asserted content of modern empirical +> science," (p 45) -1. 1. 1. Probabilistic explanations +#### Probabilistic explanations Nagel's second category, probabilistic explanations, depend not on -formal +formal implication of the explicandum by the premises contained within the +explanation, but on some 'statistical reregularity' taking the general form: -implication of the explicandum by the premises contained within the -explanation, - -but on some 'statistical reregularity' taking the general form: - -Most x are y - -a is x - -=> it is probable that a is y + Most x are y + a is x + => it is probable that a is y Nagel notes that: -"It is still an unsettled question whether an explanation must contain a -statistical assumption in order to be a probabilistic one, or whether -nonstatistical premises may make an explicandum 'probable' in some -nonstatistical sense of the word." (p 23) +> "It is still an unsettled question whether an explanation must contain a +> statistical assumption in order to be a probabilistic one, or whether +> nonstatistical premises may make an explicandum 'probable' in some +> nonstatistical sense of the word." (p 23) -such explanations can be expressed in the Toulmin scheme (see below); +Such explanations can be expressed in the Toulmin scheme (see below); but as syllogisms have the general form IAA, which is not valid. These two types are the models of scientific explanation that Nagel @@ -217,33 +205,32 @@ describes; but he also describes two other categories. These are explanation types which appear in natural conversation, and in law and the humanities. -1. 1. 1. Functional (teleological) explanations +#### Functional (teleological) explanations Functional (teleological) explanations are explanations which refer to the supposed purpose of the explicandum: -"lt is characteristic of functional explanations that they employ such -typical locutions as 'in order that', 'for the sake of' and the like." -(p 24) +> "lt is characteristic of functional explanations that they employ such +> typical locutions as 'in order that', 'for the sake of' and the like." (p 24) There are two sub classes of functional explanation. One is the explanation of a particular instance or occurrence: .. . -'I caught hold of the branch so that I would not fall.' + 'I caught hold of the branch so that I would not fall.' whereas the other explains something which occurs in all instances of a particular class: -'Birds have wings so that they can fly.' + 'Birds have wings so that they can fly.' -1. 1. 1. Genetic explanations +#### Genetic explanations Genetic explanations seek to explain why something is the way it is by explaining how it came to be this way: -'My arm is broken because I fell out of a tree' + 'My arm is broken because I fell out of a tree' -'Penguins have wings because they evolved from birds which could fly' + 'Penguins have wings because they evolved from birds which could fly' It is clear that these are categories where the explanations are neither necessary nor sufficient causes of the explicanda; you don't have to @@ -252,18 +239,18 @@ falling out. Likewise, there may have been other ways of not falling than catching hold of a branch, and catching hold of a branch may not prevent a fall. - But there are statistical probabilities (not necessarily high) that +But there are statistical probabilities (not necessarily high) that catching the branch will prevent the fall, and that a fall will lead to a broken arm. -"It is therefore a reasonable conclusion that genetic explanations are -by and large probabilistic." (p 26) +> "It is therefore a reasonable conclusion that genetic explanations are +> by and large probabilistic." (p 26) -1. 1. The radical critics +### The radical critics These conventional arguments in the philosophy of science were dramatically disturbed in the 1960s by radical philosophers like Thomas -Kuhn \[Kuhn, 62\] and Paul Feyerabend \[Feyerabend, 78; and passim\]. +Kuhn [Kuhn, 62] and Paul Feyerabend [Feyerabend, 78; and passim]. Their attack was not directed specifically at accounts of explanation, but at the empiricist and realist views of science as such - which is to say the view – implicit in both – that we can directly access the @@ -277,59 +264,61 @@ attempting to preserve a view of science which is no longer tenable. Following (but not, as far as I am aware, prior to) the radicals onslaught, writers on the philosophy of science developed a formidable arsenal of objections to the deductive-nomological account. I cite here -a few drawn from \[Korner 75\]: +a few drawn from [Korner 75]: Achinstein, in his note The Object of Explanation, gives some 'standard -counler—examp|es': +counler-examp|es': -"1\] We see a fire engine which is black and demand an explanation. Here -is one that satisfies the D-N model: +> "1\. We see a fire engine which is black and demand an explanation. Here +> is one that satisfies the D-N model: +> +>> This fire engine is the same colour as that crow. -This fire engine is the same colour as that crow. +>> All crows are black. -All crows are black. +>> =>This fire engine is black. +> +> 2\. A bridge collapses and we demand an explanation. Here is one that +> satisfies the D-N model: +> +>> An engineer with years of training and experience examined the bridge +>> and said it would collapse. -=>This fire engine is black. +>> Whenever an engineer with years of training and experience examines a +>> bridge and says it will collapse, it does. -2\] A bridge collapses and we demand an explanation, Here is one that -satisfies the D-N model: - -An engineer with years of training and experience examined the bridge -and said it would collapse. - -Whenever an engineer with years of training and experience examines a -bridge and says it will collapse, it does. - -=> The bridge collapsed. - -These are unacceptable as explanations .... " (page 35) +>> => The bridge collapsed. +> +> These are unacceptable as explanations .... " (page 35) Hesse, in her rejoinder to Achinstein, writes: - “... there are by now at least three widely accepted general +> “... there are by now at least three widely accepted general consequences of the ensuing debate which are enough to show that this model is by no means to be taken as the 'standard model of explanation'. -These are: +> These are: -(i) It has grave shortcomings as an explication of the structure of - explanation in natural science itself. -(ii) The question of whether it usefully applies to explanation in - history, psychology, and the social sciences is a matter of current - controversy. -(iii) The question of whether *any* model applying to the natural - sciences is adequate also for these human sciences is also highly - controversial." (page 46, Hesse's emphasis) +> (i) It has grave shortcomings as an explication of the structure of +> explanation in natural science itself. + +> (ii) The question of whether it usefully applies to explanation in +> history, psychology, and the social sciences is a matter of current +> controversy. + +> (iii) The question of whether *any* model applying to the natural +> sciences is adequate also for these human sciences is also highly +> controversial." (page 46, Hesse's emphasis) and finally, Salmon, in a piece entitled Theoretical Explanation, argues: -"... contra Hempel and many others - that an explanation \[of a +> "... contra Hempel and many others - that an explanation \[of a particular event\] is not 'an argument to the effect that the event to be explained was to be expected by reason of certain explanatory facts'... -In addition, I have claimed that the so-called deductive- nomological +> In addition, I have claimed that the so-called deductive- nomological model of explanation of particular events is incorrect. It is not merely that there are explanandum events which seem explainable only inductively or statistically... There are also cases – such as the man @@ -341,10 +330,87 @@ Frontiers of Science and Philosophy, University of Pittsburgh Press, Pittsburgh, 1962. The italics are Salmon's. This birth control example is also mentioned in for example van Frassen 1980) -\[Here insert some detailed analysis of Feyerabend's position, and -passing reference to Lakatos and Kuhn\] +[Here insert some detailed analysis of Feyerabend's position, and +passing reference to Lakatos and Kuhn] -1. 1. Achinstein +### van Fraassen + +Another philosopher who has attracted attention with his work on +explanation in recent years is Bas van Fraassen. His work seems directed, +however, not primarily at providing better accounts of explanation, so +much as at defending the empirical view of science from the realist critics of +it - surely, at this late date, a redundant activity. The work is marred, in my +opinion, by intellectually dishonest treatment of the radicals, to whom van Fraassen +has no honest response. + +#### van Fraassen's response to the radicals + +van Fraassen published his ‘the Scientific Image' in 1980, in the age of +Feyerabend and Kuhn. He mentions both these authors twice, and is +clearly familiar with their theses, describing Feyerabend's work as 'well known' +(page 14), and paraphrasing one of Feyerabend's central points (although +without acknowledging it): + +> "... one theory says that there are electrons, and the other says that +there may not be. Even if the observable phenomena are as Rutherford +says, the unobservable may be different. However, the positivists +would say, if you argue that way, you automatically become a prey to +scepticism. You will have to admit that there are possibilities that you +cannot prove or disprove by experiment, and so you will have to say we +cannot know what the world is like. Worse; you will have no reason to +reject any number of outlandish possibilities; demons, witchcraft, +hidden powers contirbuting to fantastic ends." (page 35, my emphasis) + +Well yes, precisely. And although it is possible that the positivists +would say it, Feyerabend did say it, repeatedly; and the choice of words seems to +me to betray a consciousness of this \[see for example Feyerabend, 81, vol 1, +foot of page 196 - which other evidence (below) shows us van Fraassen was +familiar with\]. But the only time van Fraassen addresses an argument of +Feyerabend's directly, he dismisses it as '...a totally false issue...' (page 93). +Let us look a little at the context for this. + +van Fraassen is discussing the centrality of explanation to science, +citing - and accepting - Nagel's strong claim \[Nagel 61, page 4\], and using +incidentally the same passage from Nagel as Feyerabend had used in his earlier +critique of this work \[Feyerabend 81, page 52; this paper originally published in BJPS +vol 16, 1964\] to illustrate this. He claims that Nagel's view does not entail +realism, but will equally support an empiricist view. He now claims that Feyerabend +has advanced the '..totally false..' argument that, in his paraphrase: + +> '...only Realism is a philosophy that stimulates scientific enquiry; anti-realism hampers it." \[page 93\] + +This is a position that Feyerabend advanced? Really? Feyerabend whose +central thesis might be summed up in his phrase "The only principle that +does not inhibit progress is: anything goes." \[Feyerabend 75, p10: F's +emphasis\]. van Fraassen refers us to Feyerabend's paper \[in Feyerabend 81 vol 1\]. What Feyerabend in fact says (forgive me if I +quote at length) is: + +> "To sum up: the issue between realism and instrumentalism has +A many facets..... There are arguments for instrumentalism which +concern specific theories such as the quantum theory or the +heliocentric hypothesis and which are based on specific facts and well +confirmed theories. It was shown that to demand realism in these cases +amounts to demanding support for implausible conjectures which +possess no independent empirical support and which are inconsistent +with facts and well confirmed theories. It was also shown that this is a +plausible demand which immediately follows from the principle of +testability. Hence realism is preferable to instrumentalism even in +these most difficult cases." \[Feyerabend 81 vol 1 pp 201-2; Feyerabend's emphasis.\] + +'Realism is preferable to instrumentalism'. That is a very different +(and far weaker) claim than 'only Realism stimulates scientific enquiry'. So the +totally false issue is of van Fraassen's own devising, and has nothing +to do with Feyerabend. + +I have gone on at some length about van Fraassen's slight (and +slighting) mention of Feyerabend. Why? Well, because van Fraassen, continuing the +now moribund debate between realism and empiricism in order to defend the +latter, addresses Feyerabend's criticisms of neither doctrine. This seems an +extraordinary ommission. + +<Here insert some stuff about van Fs account of explanation...> + +### Achinstein One of the first attempts to recover an account of explanation from this mess is that of Achinstein \[Achinstein 83\]. Achinstein distinguishes @@ -358,16 +424,14 @@ His project is to answer three questions: . 2. What is the product of an explaining act? 3. How should explanations be evaluated? - - -1. 1. 1. 'Explaining acts' +#### 'Explaining acts' Achinstein claims that 'explaining acts' have a period, and a completion point. -'John was explaining why x' + 'John was explaining why x' -'John explained x' + 'John explained x' The latter form implies a completion has occurred. @@ -384,14 +448,14 @@ The intention of an explaining act must be to engender understanding of the explicanda. Achinstein does not state, but may be taken to imply, that for such an act to take place there must (at any rate in the mind of the explainer) be some explainee or auditor, in whose mind -understanding is to be engendered[^1]. +understanding is to be engendered[Achinstein 1]. -"The first condition expresses what I take to be a fundamental +> "The first condition expresses what I take to be a fundamental relationship between explaining and understanding. It is that S explains q by uttering u only if -\(1) S utters u with the intention that his utterance of u render q -understandable."(Page ??) +> 1. S utters u with the intention that his utterance of u render q +understandable."(Page ??) Under this account it is impossible to explain something by accident – a rather over strict condition, l think. @@ -400,7 +464,7 @@ Achinstein also claims that it is neccesary that the utterance produced by the explaining act must be (at least believed to be) a correct account: -"(2) S believes that u expresses a proposition that is a correct answer +> "2. S believes that u expresses a proposition that is a correct answer to Q... Often people will present hints, clues, or instructions which do not @@ -413,7 +477,7 @@ strong condition. Yet Achinstein goes on to make this even stronger by the assertion that the proposition expressed by u is itself a complete answer to Q: -"(3) S utters u with the intention that his utterance render q +> "3. S utters u with the intention that his utterance render q understandable by producing the knowledge, of the proposition expressed by u, that it is a correct answer to Q."(p 18) @@ -423,7 +487,7 @@ explanation; and a more restricted sense, which will "cover only correct explainings". He does not describe how these may be differentiated, however. -1. 1. 1. Understanding +#### Understanding If explaining is to be seen as an act directed at engendering understanding, some account of what is meant by 'understanding' must be @@ -433,7 +497,7 @@ supplied. Achinstein asserts that: knows to be correct (sic)... we can say that a necessary condition for the truth of sentences of the form 'At understands q' is -\(1) (£x)(A knows of x that it is a correct answer to Q)" (p 23 - 4) +> "(∀x)(A knows of x that it is a correct answer to Q)" (p 23 - 4) Achinstein's essential problem is quite simple to express: he wants to say that one doesn't understand something until one not only knows a @@ -441,7 +505,7 @@ proposition which expresses the reason for it, and knows that this proposition does in fact express the 'correct' reason, but also has internalised this proposition. -1. 1. 1. 1. 'Content-giving Propositions' +#### 'Content-giving Propositions' Achinstein identifies a class of nouns which he describes as 'content-giving', such as 'explanation', 'meaning', 'fact', 'reason'. He @@ -449,12 +513,12 @@ then defines a class of propositions, constructed using such nouns and the verb to be, which he calls 'content-giving propositions'. These take roughly the form: -'the <cg-noun> {that | of | for} <proposition x> is -<proposition y>.' + 'the {that | of | for} is + ' Achinstein now expands his definition of understanding to: -"(∃p)(A knows of p that it is a correct answer to Q, and p is a complete +> "(∃p)(A knows of p that it is a correct answer to Q, and p is a complete content-giving proposition with respect to Q)" (p 42) . Achinstein examines a number or accounts of the epistemic nature of an @@ -466,8 +530,8 @@ These are rejected for reasons which appear to me quite strange. Achinstein has trouble with the idea that two sentences can be differently constructed but have the same meaning. E.g.: -"...since sentence (1) ≠ sentence (2), the explanation of Bill's stomach -ache given by Dr. \_Smith ≠ the explanation of Bill's stomach ache given +>"...since sentence (1) ≠ sentence (2), the explanation of Bill's stomach +ache given by Dr. Smith ≠ the explanation of Bill's stomach ache given by Dr. Robinson, which seems unsatisfactory. Intuitively, both doctors have given the same explanation..."(p 76) @@ -477,7 +541,7 @@ not sufficient for him to posit that such a thing must exist; so he claims that behind every sentence there is a (presumably unique) proposition, in English. Thus: -"Since sentences (1) and (2) express the same proposition we can +> "Since sentences (1) and (2) express the same proposition we can conclude that the explanations given by the doctors are the same."(p 76) For evidence that the proposition is considered to be unique, see the @@ -490,7 +554,7 @@ which map onto the same proposition, then that proposition is at once a criticism and an explanation, which is absurd. Therefore the product of an explanation cannot be a proposition. -l doubt whether this argument has meaning, let alone force. ln this and +I doubt whether this argument has meaning, let alone force. ln this and other arguments, Achinstein seems to confound operations which would be legitimate on some formal grammar with what it is possible to do with natural language. @@ -502,67 +566,38 @@ that sequences of symbols are efficient (i.e. that they may have many differing meanings), see e.g. \[Barwise and Perry 86, p S2\]; , He also has trouble with emphasis shifts in propositions which are - represented by the same sequence of word-tokens, which he resolves by -the +the concept of 'e-sentences' - sentences with additional flagging to +indicate the central phrase, so that: -concept of 'e-sentences' - sentences with additional flagging to -indicate the +> "(7) the e-sentence 'Bill ate *spoiled meat* on Tuesday' is not identical with +> (8) the e-sentence 'Bill ate spoiled meat *on Tuesday*"' (p 80) -central phrase, so that: - -"(7) the e-sentence 'Bill ate spoiled meat on Tuesday' is not - -identical with - -8 (8) the e-sentence 'Bill ate spoiled meat on Tuesday"' (p 80) - -He next considers the deductive-nomological view - the view that an - -' explanation is an argument. +He next considers the deductive-nomological view - the view that an explanation is an argument. Achinstein argues that the form of the deductive nomological explanation -can +can be seen as an ordered pair <conjunction of premises, conclusion>. +This view is dismissed for reasons analogous to those above. -be seen as an ordered pair <conjunction of premises, conclusion>. -This view is - -dismissed for reasons analogous to those above. - -Explanation as ordered pair +#### Explanation as ordered pair Having considered, and dismissed, the preceding accounts of explanation, -A. - -\_ now proposes that explanation should be considered to be an ordered +Achinstein now proposes that explanation should be considered to be an ordered pair <x, y> -s.t.: . +s.t.: -"'The explanation of q given by S denotes (x; y) if and only if - -\(i) Q is a content-question; - -\(ii) x is a complete content-giving proposition with respect to Q; - -\(iii) y = explaining q; \` - -\(iv) (£a)(£u)\[a is an act in which S explained q by uttering u -> - -(r)(r is associated with with a;r=x)\]. (i.e., x is the one and only - -A proposition associated with every act in which S explained q by \` - -uttering something.)"(p 87) \_ +> "The explanation of q given by S denotes (x; y) if and only if +> +> (i) Q is a content-question; +> (ii) x is a complete content-giving proposition with respect to Q; +> (iii) y = explaining q; +> (iv) (£a)(£u)\[a is an act in which S explained q by uttering u -> (r)(r is associated with with a;r=x)\]. (i.e., x is the one and only A proposition associated with every act in which S explained q by \`uttering something.)"(p 87) What this appears to boil down to is this: -Achinstein believes any given concatenation of symbols representing a - -" proposition to be identical with that proposition; and that any -proposition is - -uniquel. · +Achinstein believes any given concatenation of symbols representing a proposition to be identical with that proposition; and that any +proposition is unique. Thus each and every occurance of this sequence of symbols is the same thing. @@ -570,1100 +605,458 @@ thing. Yet he believes, as shown above, that it is impossible for (e.g.) an explanation to -lln fact, Achinstein's claim is even stronger than this, for he believes -that there is some - -proposition 'underneath' each sentence; thus, potentially, many -sentences may map onto - -the same proposition, and consequently all these sentences may be -treated as being - -identical (l). - -Simon Brooke: Notes for a thesis entitled Page : 34 - -Meghaniseq Inference and Explanation Draught dated ; 2\]{§\[§§ +In fact, Achinstein's claim is even stronger than this, for he believes +that there is some proposition 'underneath' each sentence; thus, potentially, many +sentences may map onto the same proposition, and consequently all these sentences may be +treated as being identical (l). be 'the same thing' as (e.g.) a criticism. So it is impossible for an -explanation to - -be identical with an occurance of a sequence of symbols. +explanation to be identical with an occurance of a sequence of symbols. Thus an ordered pair must be constructed, in which the symbol-sequence -is - -linked with another symbol sequence which represents a reference to the - +is linked with another symbol sequence which represents a reference to the question which was asked. Note that q, the question, is also a sequence of symbols; so that a pair: -<\[aI| plants are green\]; \[answering: "why is this grass +<\[all plants are green\]; \[answering: "why is this grass green"\]> . is unique, and is always the same explanation. Therefore (since -Achinstein'S4» gp - -schema makes no mention of an auditor) it is always either a good -explanation or - -a bad one, regardless of whether the question was asked by a three year -old child - -or a plant physiologist. +Achinstein's schema makes no mention of an auditor) it is always either a good +explanation or always a bad one, regardless of whether the question was asked by a three year +old child or a plant physiologist. I would like to return the readers attention to Achinstein's claim that: -"One understands q only if one knows a correct answer to Q which - -one knows to be correct " \[p 23, my emphasis\] +> "One understands q only if one knows a correct answer to Q which one knows to be correct " \[p 23, my emphasis\] and goes on to clarify that, by this, he implies '...a de re sense of -knowing.' as - -" The use of 'correct' here is the problem. It appears to imply that one -knows that - -the answer which one knows maps in some unproblematic way onto something +knowing.' +The use of 'correct' here is the problem. It appears to imply that one +knows that the answer which one knows maps in some unproblematic way onto something real in the external world. Thus Achinstein, too, falls into the trap -sprung by the +sprung by the radicals. In the absence of some definition of what is to be understood +by 'correct', these definitions are simply meaningless. -radicals. ln the absence of some definition of what is to be understood -by - -'correct', these definitions are simply meaningless. - - ·; ; —• ·\_ gt g J; rg FQ :r. ns .· efbr ¢'<—¤ · S = " . \~w’ ll’ - -9 (v x \~ J · 'Q\~ k. , l 6 4 4 - -P7 » %‘· both orde al ;/ an ns (parables s ve. - -‘ This account does not address many of the facets of common sense +This account does not address many of the facets of common sense explanation. It has nothing to say about the amount of detail contained in an -explanation. It has - -nothing to say about the need to express an explanation in terms of an -account of - -the world which is accessible to the auditor. lt fails to account for -the possibility - -of explanation by analogy, or of unintentional explanation. +explanation. It has nothing to say about the need to express an explanation in terms of an +account of the world which is accessible to the auditor. lt fails to account for +the possibility of explanation by analogy, or of unintentional explanation. It appears that Achinstein's motivation in producing a new account has -less to - -do with addressing these real world problems than with overcoming such - +less to do with addressing these real world problems than with overcoming such philosophical puzzles as the Paradox of the Ravens; so his account takes -us no - -nearer to providing a model which will support the construction of -better - -common sense explanations. 5 +us no nearer to providing a model which will support the construction of +better common sense explanations. 5 A \[ mh L/Go/w%\` \\ \` Eegozi -van Fraassen Arclltuqrfélv -\_ Another philosopher who has attracted attention with his work on -explanation - -in recent years is Bas van Fraassen. His work seems MNMW directed, -trbeislz - -however, not primarily at providing better accounts of explanation, so -much as - -at defending the empirical view of science from the realist critics of -it - surely, - -at this late date, a redundant activity. The work is marred, in my -opinion, by - -intellectually dishonest treatment of the radicals, to whom van Fraassen -has no - -honest response. - -van Fraassen's response to the radicals - -van Fraassen published his ‘the Scientific Image' in 1980, in the age of - -Feyerabend and Kuhn. He mentions both these authors twice, and is -clearly - -familiar with their theses, describing Feyerabend's work as 'well known' -(page - -Simon Brooke: Notes for a thesis entitled Page : 35 - -l· 1¤ ·•I f I‘ · - • sustai n !q.u •q·• •\$€ - -14), and paraphrasing one of Feyerabend's central points (although -without - -acknowledging it): l - -"... one theory says that there are electrons, and the other says that - -there may not be. Even if the observable phenomena are as Rutherford - -says, the unobservable may be different. However, the positivists - -would say, if you argue that way, you automatically become a prey to - -scepticism. You will have to admit that there are possibilities that you - -cannot prove or disprove by experiment, and so you will have to say we - -cannot know what the world is like. Worse; you will have no reason to - -reject any number of outlandish possibilities; demons, witchcraft, - -hidden powers contirbuting to fantastic ends." (page 35, my emphasis) - -Well yes, precisely. And although it is possible that the positivists -would say - -it, Feyerabend did say it, repeatedly; and the choice of words seems to -me to - -betray a consciousness of this \[see for example Feyerabend, 81, vol 1, -foot of - -page 196 - which other evidence (below) shows us van Fraassen was -familiar - -with\]. But the only time van Fraassen addresses an argument of -Feyerabend's - -directly, he dismisses it as '...a totally false issue...' (page 93). -Let us look a - -P little at the context for this. 3 - -van Fraassen is discussing the centrality of explanation to science, -citing - - -and accepting - Nagel's strong claim \[Nagel 61, page 4\], and using -incidentally - -the same passage from Nagel as Feyerabend had used in his earlier -critique of this - -work \[Feyerabend 81, page 52; this paper originally published in BJPS -vol 16, - -1964\] to illustrate this. He claims that Nagel's view does not entail -realism, but - -will equally support an empiricist view. He now claims that Feyerabend -has - -advanced the '..totally false..' argument that, in his paraphrase: - -'...only Realism is a philosophy that stimulates scientific enquiry; - -anti-realism hampers it." \[page 93\] - -This is a position that Feyerabend advanced? Really? Feyerabend whose - -central thesis might be summed up in his phrase "The only principle that -does - -not inhibit progress is: anything goes." \[Feyerabend 75, p10: F's -emphasis\]. van - -Fraassen refers us to Feyerabend's paper \[in - -Feyerabend 81 vol 1\]. What Feyerabend in fact says (forgive me ifi -quote at - -length) is: - -"To sum up: the issue between realism and instrumentalism has g\` - -A many facets..... There are arguments for instrumentalism which - -concern specific theories such as the quantum theory or the - -heliocentric hypothesis and which are based on specific facts and well - -confirmed theories. It was shown that to demand realism in these cases - -\* amounts to demanding support for implausible conjectures which - -possess no independent empirical support and which are inconsistent - -with facts and well confirmed theories. It was also shown that this is a - -plausible demand which immediately follows from the principle of - -testability. Hence realism is preferable to instrumentalism even in - -these most difficult cases." \[Feyerabend 81 vol 1 pp 201-2; - -Feyerabend's emphasis. - -'Realism is preferable to instrumentalism'. That is a very different -(and far - -weaker) claim than 'only Realism stimulates scientific enquiry'. So the - -totally false issue is of van Fraassen's own devising, and has nothing -to do with - -Feyerabend. - -Simon Brooke: Notes for a thesis entitled Page : 36 - -ll‘ tan ·• l“\`l · anu, ne u lan uw •\$¢ - -l have gone on at some length about van Fraassen's slight (and -slighting) - -mention of Feyerabend. Why? Well, because van Fraassen, continueing the -now - -moribund debate between realsim and empiricism in order to defend the -latter, - -addresses Feyerabend's criticisms of neither doctrine. This seems an - -extraordinary ommission. - -<Here insert some stuff about van Fs account of exp/anati0n...> - -Toulmin +## Toulmin Turning aside for the moment from those philosophers who have made a -study VcL‘&‘/6 - -of explanation per se, there is another whose work is currently -attracting - -fashionable attention in Expert Systems (and especially mechanised -explanation) - -circles; one must make passing reference to Toulmin, and, unless one -chooses to - -use his argument schema, one must produce a very good argument for not -doing - -so. Therfore it is important to know what he actually argued. - -A Tou|min's programme was to replace the syllogistic with a new logical +study of explanation per se, there is another whose work is currently +attracting fashionable attention in Expert Systems (and especially mechanised +explanation) circles; one must make passing reference to Toulmin, and, unless one +chooses to use his argument schema, one must produce a very good argument for not +doing so. Therfore it is important to know what he actually argued. +A Toulmin's programme was to replace the syllogistic with a new logical schema of his own. He did not address symbolic logic except by -dismissing it as - -irrelevant to the study of real world arguments: - -"We shall have to replace mathematically-idealised logical +dismissing it as irrelevant to the study of real world arguments: +> "We shall have to replace mathematically-idealised logical relations - timeless context-free relations between either statements - or propositions — by relations which in practical fact are no more than - the statements to which they relate. This is not to say that the - elaborate mathematical systems which constitute 'symbolic logic' must - now be thrown away; but only that people with intellectual capital - invested in them should retain no illusions about the extent of their - relevance to practical arguments." (Toulmin 58, p 185) or again: -"...the question needs to be pressed, whether this branch of - +> "...the question needs to be pressed, whether this branch of mathematics (propositional calculus) is entitled to the name 'logical - theory'. If we give it this name, we imply that the propositional - calculus plays a part in the assessment of actual arguments comparable - to that played by physical theory in explaining actual physical - -phenomena. But this we have seen reason to doubt: this branch of \~ - -" mathematics does not form the theoretical part of logic... By now, the - +phenomena. But this we have seen reason to doubt: this branch of +mathematics does not form the theoretical part of logic... By now, the mathematicians logic has become a frozen calculus, having no - functional connection with the canons for assessing the strength and +cogency of arguments." (Ibid, p 186 - and he goes on in this vein!) -\_\` cogency of arguments." (Ibid, p 186 - and he goes on in this vein!) +**TODO**: I can use precisely this - and van Frassen's work, too - to illustrate and underline my case later that the purpose of argument is hegemonistic, not truth-seeking. This is so clearly polemical. These contentions seem polemical, even propagandistic, in tone; they are - certainly not, in Tou|min‘s own terminology, 'candid'. They advance -scant - -evidence in support of their allegations. They seem out of place in a -work whose - -matter is the analysis of argument; and they lie especially uneasy with -TouImin's - -claim to be seeking to make argument more scrutable. +scant evidence in support of their allegations. They seem out of place in a +work whose matter is the analysis of argument; and they lie especially uneasy with +Touimin's claim to be seeking to make argument more scrutable. He goes on to attack the concept of ‘logicaI form' and 'formal validity' -in - -argument: - -Simon Brooke: Notes for a thesis entitled Page : 37 - -1: nan ·•. · ·n · an ,...».ent -1 U an u ·•. 1- \$3 - -"...the suggestion that validity is to be explained in terms of +in argument: +> "...the suggestion that validity is to be explained in terms of 'formal properties', in any geometric sense, loses its plausibility." - (Ibid, p 120) He argues that the conception that arguments in general could or should -have a - -logical form arises out of a false start in the study of logic: - -"The development of logical theory... began historically with the +have a logical form arises out of a false start in the study of logic: +> "The development of logical theory... began historically with the study of a rather special class of arguments -\_ namely, the class of - unequivocal, analytic, formally valid arguments with a universal - statement as 'major premiss'. Arguments in this class are exceptional - in four different ways, which together make them a bad example for - general study." (Ibid, p 144) Clearly, if arguments have no logical form, it is not possible to -advance a - -decision process for them, and Toulmin does not attempt to do so. -Rather, the - -burden of his argument is that decision processes are (for real world -arguments) - -impossible in principle. +advance a decision process for them, and Toulmin does not attempt to do so. +Rather, the burden of his argument is that decision processes are (for real world +arguments) impossible in principle. Thus those practitioners in the field of Expert Systems who advance -Toulmin - -,·— as an authority must face up to this corrolary: if Toulmin's -arguments are valid, - -then there cannot ever be a successful Expert System based on any -technology we - -have now available, as all current Expert Systems are based on some -logical - -formalism (even if, as in the case of production systems, this formalism -is - -crude); and all, certainly, claim to be decision processes for arguments -in their - -domain. As such, according to Toulmin, they are the modern equivalents -of the - -PhiIosophers' stone - they cannot exist. +Toulmin as an authority must face up to this corrolary: if Toulmin's +arguments are valid, then there cannot ever be a successful Expert System based on any +technology we have now available, as all current Expert Systems are based on some +logical formalism (even if, as in the case of production systems, this formalism +is crude); and all, certainly, claim to be decision processes for arguments +in their domain. As such, according to Toulmin, they are the modern equivalents +of the PhiIosophers' stone - they cannot exist. He was, to be fair to him, writing in the year that LISP was being -developed, - -when the posibility of mechanical inference was dreamed of only by -visionaries - -like Turing; nevertheless the cavalier manner in which he dismisses all -of the - -19th and 20th century advances in logic significantly weakens his claims -to be - -taken seriously in this field. +developed, when the posibility of mechanical inference was dreamed of only by +visionaries like Turing; nevertheless the cavalier manner in which he dismisses all +of the 19th and 20th century advances in logic significantly weakens his claims +to be taken seriously in this field. But if Toulmin cannot be taken seriously as a logician, is there any -residual +residual value in his work on argument? I think it is possible that there is, +because the argument schema with which he hoped to replace both the traditional +syllogism, and the formalisms of modern logic, does indeed capture the content of +normal conversational discussion in an easily manageable form. Had Toulmin +advanced this and this only, I think he might have been taken more seriously; and +I think there is merit in the current revival of interest in it. -value in his work on argument? I think it is possible that there is, -because the - -argument schema with which he hoped to replace both the traditional -syllogism, - -and the formalisms of modern logic, does indeed capture the content of -normal - -conversational discussion in an easily manageable form. Had Toulmin -advanced - -this and this only, I think he might have been taken more seriously; and -I think x - -A there is merit in the current revival of interest in it. - -the Schema +### The Schema Toulmin's concern is with arguments as they are presented informally, in - -\* conversation or writing, and the relation between the form of such -informal - -arguments and the forms recognised by formal logic. \` +conversation or writing, and the relation between the form of such +informal arguments and the forms recognised by formal logic. He questions whether the aristotelian 'standard form' of an argument is - 'candid'; that is, whether it is presented in such a way as to make its -merits as - -argument most manifest. He suggests that the analysis into only three -elements, - -major premiss, minor premiss, conclusion may be artificially simplified: - -"Simplicity is of course a merit, but may it not in this case have +merits as argument most manifest. He suggests that the analysis into only three +elements, major premiss, minor premiss, conclusion may be artificially simplified: +> "Simplicity is of course a merit, but may it not in this case have been bought too dearly? Can we properly classify all the elements in - our arguments under the three headings, 'major premiss', 'minor - premiss' and 'conclusion', or are these categories misleadingly few in - -Simon Brooke: Notes for a thesis entitled Page : 38 - -U' al. “! ‘·1 · any t •n |»•1 •qf•. •¢\$ - number? Is there even enough similarity between major and minor - premisses for them usefully to be yoked together by the single - name...?" He draws on the practice of jurisprudence to find alternative schemae; -and +and synthesises one such comprising the following elements: a statement of +some assertion, which implicitly carries with it a claim as to the +truth of the assertion; and data, information which is consensual at the time of +argument (or is supported by some futher argument), which tends to support that +claim; some inference rule, a warrant, which will allow the argument to move from +the data to the claim (for example, 'all as are bs'), again optionally supported +by some further argument or bagking; an optional qualifier (e.g. 'probably', 'I +believe'); and, implicit in the qualifier, the possibility of a rebuttal: -synthesises one such comprising the following elements: a statement of -some - -assertion, which implicitly carries with it a g\_|\_a\_j\_m\_ as to the -truth of the - -assertion; and data, information which is consensual at the time of -argument (or - -is supported by some futher argument), which tends to support that -claim; some - -inference rule, a warrant, which will allow the argument to move from -the data - -to the claim (for example, 'all as are bs'), again optionally supported -by some - -further argument or bagking; an optional ggjalifigr (e.g. 'probably', 'l -believe'); - -and, implicit in the qualifier, the possibility of a rebuttal: - -D —------------··-— > S0, O , C - -I I - -I I - -Since Un/ess - -' W F? - -I - -on account of - -B - -(after Toulmin, p 104: my emphasis of optional elements) +![Argument schama after Toulmin, p 104](../img/toulmin-argument-schema.svg) In conversation, Toulmin argues, it may be natural simply to say -'<data> so - -<c|aim>' ; to say '<c|aim> because <warrant> because -<data>' "...strikes us as - -cumbrous and artificial, for it\_puts in an extra step which is trivial -and - -unnecessary". +'<data> so <c|aim>' ; to say '<c|aim> because <warrant> because +<data>' "...strikes us as cumbrous and artificial, for it puts in an extra step which is trivial +and unnecessary". Toulmin sets out to validate this schema by comparing it with the -syllogism, +syllogism, and asking "'What corresponds in the syllogism to our distinction +between data, warrant, and backing?"' He devotes special attention to arguments of the +forms 'Almost all A's are B's' and 'Scarcely any A's \_are B's' - forms which +are, of course, of the utmost importance in default logics, but which are beyond +the scope of the syllogistic. He shows that such arguments are representable +using his schema without difficulty, and that the traditional syllogism forms +are also so representable. -and asking "'What corresponds in the syllogism to our distinction -between data, +But beyond this he observes that the major premiss of a syllogism +plays a dual role with hegemonistic implications: it is at once an inference +step and an assertion of some piece of information. Thus one may challenge it in its +role as warrant, on the basis that it is not relevant to the case, and as +backing, on the grounds that it is not true. TouImin's schema, by separating these +roles, makes clearer from what grounds a counter argument can be launched. -warrant, and backing?"' He devotes special attention to arguments of the -forms - -'Almost all A's are B's' and 'Scarcely any A's \_are B's' - forms which -are, of - -course, of the utmost importance in default logics, but which are beyond -the - -scope of the syllogistic. He shows that such arguments are representable -using - -his schema without difficulty, and that the traditional syllogism forms -are also so - -representable. - -f But beyond this he observes that the major premiss of a syllogism -plays a - -dual role with hegemonistic implications: it is at once an inference -step and an - -assertion of some piece of information. Thus one may challenge it in its -role as - -\_; warrant, on the basis that it is not relevant to the case, and as -backing, on the - -grounds that it is not true. TouImin's schema, by separating these -roles, makes \` . \_ E - -clearer from what grounds a counter argument can be launched. °\_ i.\_ -\` \` +{**TODO**: Again back-reference this when I'm arguing that argument is hegemonistic!} While TouImin's ambitious claims for his schema as the authoritative -tt-, . \_ f, - representation of argument - and his audacious dismissal of modern logic -- seem Q\_ A »\_ ·\_ · - -unworthy of attention, his representation shema does offer some merits -in the W ; ‘ \\ M I - -representation of real world arguments, especially those which appeal to -default .»—l— .,,\_ - -reasoning. Furthermore, the fact that these argument structures can be -'daisy- - -. chained' offers a convenient way to pack up large arguments into a -structure - -which can be unfolded to any given level of detail, and this property -makes the - -Simon urookez Notes ror a tnesns emmeo r-age ; eu - -· {n w 1.··1· qa .• ·n. •n |·.•n nv . •\$\$ - -schema an interesting candidate argument representation as we look for -ways to - -control the amount of detail revealed to the user of an Expert System. +- seem unworthy of attention, his representation schema does offer some merits +in the representation of real world arguments, especially those which appeal to +default reasoning. Furthermore, the fact that these argument structures can be +'daisy-chained' offers a convenient way to pack up large arguments into a +structure which can be unfolded to any given level of detail, and this property +makes the schema an interesting candidate argument representation as we look for +ways to control the amount of detail revealed to the user of an Expert System. His contention that argument can be hegemonic is one which I shall want -to +to examine further. -examine further. - -Towards a Situation Semantic account of Explanation +## Towards a Situation Semantic account of Explanation Part of Barwise and Perry's programme in constructing Situation -Semantics - -was to elucidate the problem of the transfer of knowledge from one -person to - -another, and this is, of course, one of the central problems in an -account of - -explanation. +Semantics was to elucidate the problem of the transfer of knowledge from one +person to another, and this is, of course, one of the central problems in an +account of explanation. However, they give no account of explanation as such. What follows is my - guess at what their account would look like, had they formally stated -it. This - -should not be taken too seriously, as their formalism is rich and -complex, and I - -have by no means mastered it. Certainly, any howlers in what follows all -my own - -work. \` +it. This should not be taken too seriously, as their formalism is rich and +complex, and I have by no means mastered it. Certainly, any howlers in what follows all +my own work. My first ‘cut’ at the problem looked like this. An explanation was to be -that +that which happened in a situation E defined: -which happened in a situation E defined: + E := at I1: understands, a, c; no + understands, b, c; yes + enquirlng, a; yes + addressing, a, b; yes + saying, a, q; yes + subject, q, c; yes -° E := at jj: understands, \_a, gg no + at I2: responding, b, q; yes + addressing, b, a; yes + saying, b, u; yes + subject, u, c; yes -understands, p\_, \_c\_; yes + at I3: understands, a, c; yes + understands, b, c; yes -enquirlng, g; yes + I1 < I2 < I3 -addressing, \_a\_, \_b\_; yes - -S¤Yl¤9. Q. 9; l/GS - -subject, g, g; yes - -atlz: responding, bi, g; yes - -addressing, \_b\_, a\_; yes - -\$¤Yl¤9. 9.. ll; VSS - -subject, \_u, jg; yes - -atj3: understands, gd, g; yes - -understands, p\_, \_c\_; yes \` - -I1 \`< lz '<Is - -»» where: a, b are some actors; c is some concept; q, u are some -utterances. " +where: a, b are some actors; c is some concept; q, u are some +utterances. This begs a number of questions. Firstly, what relationship is meant by - ’understands, x, y' ? This question is, of course, the central one for -the whole - -programme of Situation Semantics; when it can be answered, the programme - -\*1 will have succeeded. Secondly, how can we represent the (presumed) -causal - -dependence of the understanding at I3 on the responding at I2 ? Thirdly, -what - -implications (if any) does this have for the semantic content of u? +the whole programme of Situation Semantics; when it can be answered, the programme +will have succeeded. Secondly, how can we represent the (presumed) +causal dependence of the understanding at I3 on the responding at I2 ? Thirdly, +what implications (if any) does this have for the semantic content of u? However, this definition does have some points of value. Firstly, an - explanation is located in a situation with at least two roles (which, - incidentally, cannot be taken by the same individual); secondly, a -transfer of - -understanding takes place. Neither of these points are met by -traditional - -accounts. +transfer of understanding takes place. Neither of these points are met by +traditional accounts. So what we need to add is something like this. The sage's response, u, -must +must be seen as a list of statements \[s1, s2, ... sn\], Such that, for any +statement sj in u, sj is understandable in terms of \[<student's state of knowledge +at I1> + s1 + Sj-1\]. and also that c, the concept originally asked about, is +understandable in terms of \[<student's state of knowledge at I1> + +sj + ... + sn\]. This (fortunately) accords with Barwise and Perry's understanding: -be seen as a list of statements \[sq, sg, sn\], Such that, for any -statement sj - -Simon Brooke: Notes for a thesis entitled Page : 40 - -ll: ·.¤ ‘• .|.<·n · aan .•tn» •n |q•1 •··• •\$\$ - -in u, sj is understandable in terms of \[<students state of knowledge -at l1> + sj - -+ + Sl-1\]. and also that c, the concept originally asked about, is - -understandable in-terms of \[<students state of knowledge at l1> + -sj + + - -sn\]. This (fortunately) accords with Barwise and Perry's understanding: - -"An utterance u of a sentence l/I gives us not just one discourse \_ - -situation d for 1/J that is part of u, but also discourse situations d G -for - -every constituent expression 0 of ltr, discourse situations that are -also - -parts of u... Thus, part of what the utterance gives us is the set - -{d G : cz is zlr or a constituent of lp} - -of discourse situations." \[Ibid p 123\] +> "An utterance u of a sentence φ gives us not just one discourse +situation d for φ that is part of u, but also discourse situations dα +for every constituent expression α of φ, discourse situations that are +also parts of u... Thus, part of what the utterance gives us is the set +> +> {dα : α is φ or a constituent of φ} +> +> of discourse situations." \[Ibid p 123\] This is inadequate, because (among other things) it fails to represent -the - -negotiation which is inherent in the construction of many real world - +the negotiation which is inherent in the construction of many real world explanations. However, it appears to be a step along a potentially interesting path, -and +and one which I intend to pursue. -one which I intend to pursue. +## A lemma concerning the nature of perception -A lemma eeneerning the natjjre ef pereeptign - -The major argument which l wish to develop in this chapter is based on a -very - -important - and contentious - assumption: there may (or may not) be such -a thing - -as a real world, but it's existance is largely irrelevant, as if it does -exist, we are - -unable to percieve it directly. So before going on to advance this major -argument, l - -will attempt to support this lemma. +The major argument which I wish to develop in this chapter is based on a +very important - and contentious - assumption: there may (or may not) be such +a thing as a real world, but it's existance is largely irrelevant, as if it does +exist, we are unable to percieve it directly. So before going on to advance this major +argument, I will attempt to support this lemma. In van Fraassen's words, "the human organism is, from the point of view -of - -physics, a certain kind of measuring apparatus. As such, it has certain -inherent - -|imitations... " \[van Fraassen 80, p 17\] Precisely: and as van -Fraassen observes, - -our perceptions of the world are conditioned by the nature of this -apparatus, and by - -these limitations, which, as he goes on to claim, "...wilI be described -in the final - -physics and biology." \[ibid\] But how can this be? We are to -investigate the nature of - -these instruments, using, as analytic tools, the instruments themselves. +of physics, a certain kind of measuring apparatus. As such, it has certain +inherent limitations... " \[van Fraassen 80, p 17\] Precisely: and as van +Fraassen observes, our perceptions of the world are conditioned by the nature of this +apparatus, and by these limitations, which, as he goes on to claim, "...wilI be described +in the final physics and biology." \[ibid\] But how can this be? We are to +investigate the nature of these instruments, using, as analytic tools, the instruments themselves. Take for example the human eye. We know what the eye looks like; we've -seen - -many of them: with our eyes. We know their physical nature, because -biologists have - -dissected them, and using their eyes, have made careful diagrammes of -what they 7; - -A have seen, which we, in turn, can examine using our eyes. F \` +seen many of them: with our eyes. We know their physical nature, because +biologists have dissected them, and using their eyes, have made careful diagrams of +what they have seen, which we, in turn, can examine using our eyes. So, if our theories about the nature of the eye are right, and it does -indeed - -project a two dimensional image of a three dimensional world (supposing -such - -at exists) onto our retinas, then our theories about the nature of the +indeed project a two dimensional image of a three dimensional world (supposing +such at exists) onto our retinas, then our theories about the nature of the eye are right. This argument is not as far fetched as it sounds: after all, the memory -of a - -computer \[assuming, for the moment, that such things exist\] is -strictly one - -dimensional - a vector of cells. Yet Computer-aided design software, for -example, or - -flight simulator software, renders an image from this one-dimensional -environment - -onto a two dimensional screen in such a way that we interpret it in +of a computer \[assuming, for the moment, that such things exist\] is +strictly one dimensional - a vector of cells. Yet Computer-aided design software, for +example, or flight simulator software, renders an image from this one-dimensional +environment onto a two dimensional screen in such a way that we interpret it in three dimensions. -Simon Brooke: Notes for a thesis entitled Page : 41 - -Meclgegieeg lgteregce egg Explegeticg Qragghtegtegj ·, 21\[§\[§§ - If such transformations between a one dimensional reality and a three -dimensional - -appearance are possible in a machine, why not in our own optical -systems?1 +dimensional appearance are possible in a machine, why not in our own optical +systems? [1] Furthermore, our theories about the nature of world are conditioned by -the +the languages in which we express them. Different languages allow for the +description of different theories about reality. Again, different communities (or even +individuals) using what they believe to be the same language (say, for example, +English) may attatch sufficiently different interpretations to the same linguistic +symbols and constructs that communication fails, without either of the parties being +aware that it has failed. This point, about the incommensurability of (some) +theories has been made many times \[see eg Kuhn, Feyerabend\]; but some of the +consequences require exploration. -languages in which we express them. Different languages allow for the -descrition of - -different theories about reality. Again, different communities (or even -individuals) - -using what they believe to be the same language (say, for example, -English) may - -attatch sufficiently different interpretations to the same linguistic -symbols and - -constructs that communication fails, without either of the parties being -aware that - -it has failed. This point, about the incommensurability of (some) -theories has been - -made many times \[see eg Kuhn, Feyerabend\]; but some of the -consequences require - -exploration. - -An erggment cencerning the netgre cf explgneticn +## An argument concerning the nature of explanation Firstly, if we cannot access reality except through the medium of -theory, then - -Nagel's claim that an explanation is a mapping from a statement to +theory, then Nagel's claim that an explanation is a mapping from a statement to reality must fall. It becomes clear that explanation can at best be a mapping from a -statement to a - -theory. ls this a good account of the nature of explanation? . - -A Well, let us consider what, in common sense, we think of as 'a good -explanation'. - -We feel we have recieved a good explanation if we 'understand' both the -explanation - -and the explicandum; if it 'makes sense': if, in fact, we do not -percieve it as grossly - -inconsistent with the body of 'be|ief' or 'know|edge’ which we already +statement to a theory. ls this a good account of the nature of explanation? . +Well, let us consider what, in common sense, we think of as 'a good +explanation'. We feel we have recieved a good explanation if we 'understand' both the +explanation and the explicandum; if it 'makes sense': if, in fact, we do not +percieve it as grossly inconsistent with the body of 'belief' or 'knowledge’ which we already hold. For example, most modern Western people would not think that the statement: -'the God Fla drives his chariot daily across the rainbow bridge' + 'the God Ra drives his chariot daily across the rainbow bridge' was a good explanation of why the sun rises and sets; we do not believe -that there - -is a God Fla, nor that what we percieve as the sun is identical with -this being, nor - -that a rainbow is sufficiently rigid and strong to bear the weight of -such a being, - -lThis argument that our perception of a 'real world' does not prove its -existence is not - -new, of course. Here is a classic statement of a similar argument from -BerkeIey's Fire; - -Dielegge cf Hylee end Philcnegcz - -Hyl.: Do we not perceive the stars and moon, for example, to be a - -A great way off? Is not this, I say, manifest to the senses? I - -Phil.: Do you not in a dream too perceive those or like objects? - -Hyl.: I do. - -)‘ Phil.: And have they not then the same appearance of distance? - -Hyl.: They have. - -Phil.: But you do not htence conclude the apparitions in a dream to -q..;F - -be without the mind? - -Hyl.: By no means. - -Phil.: You ought not therefore to conclude that sensible objects are - -without the mind, from their appearance or manner wherein they are - -percieved. - -Hyl.: I acknowledge it. - -Simon Brooke: Notes for a thesis entitled Page : 42 - -should it exist. But to a first kingdom Egyptian, it may have been an -excellent - -explanation. Similarly, that first kingdom Egyptian would not accept the +that there is a God Ra, nor that what we percieve as the sun is identical with +this being, nor that a rainbow is sufficiently rigid and strong to bear the weight of +such a being should it exist. But to a first kingdom Egyptian, it may have been an +excellent explanation. Similarly, that first kingdom Egyptian would not accept the statement: -'the Earth rotates on its axis once every day' + 'the Earth rotates on its axis once every day' as a good explanation for the occurance of the same phenomenon. He would -know - -perfectly well that the earth, being fixed, could not rotate on its -axis. And even if it - -could, why should this influence the daily ritual of Ra? +know perfectly well that the earth, being fixed, could not rotate on its +axis. And even if it could, why should this influence the daily ritual of Ra? We consider an explanation good if it maps a statement about -theexplicandum - -onto the theory, or body of belief, which we currently ho|d.1 +the explicandum onto the theory, or body of belief, which we currently hold. \[Main text of argument. In the tradition of 'philosophy of science' I -intend to - -draw on examples from two genuine debates, drawn in this instance from -the - -development of the theory of evolution. These debates are +intend to draw on examples from two genuine debates, drawn in this instance from +the development of the theory of evolution. These debates are The debate between Huxley and Kropotkin over whether co-operation or - competition was the more important factor in the survival of species. Kropotkin, a leading Anarchist, sought to show that human beings (among - other animals) were inherently co-operative, and (implied conclusion) +would get along fine in the absence of government. Huxley, a Tory, +sought to show that, on the contrary, competition (and, implicitly, capitalism) +red in tooth and claw was 'natural'. -»· would get along fine in the absence of government. Huxley, a Tory, -sought to - -show that, on the contrary, competition (and, implicitly, capitalism) -red in - -tooth and claw was 'natural'. - -The debate between Bateson and Kammerer over whether aquired - +The debate between Bateson and Kammerer over whether acquired characteristics were inherited. Kammerer, then the only scientist capable of breeding many species of - amphibian in captivity, showed in a series of experiments that - characteristics aquired by parents were inherited by their offspring. - Bateson, in a series of increasingly virulent attacks, ultimately -claimed that - -these experiments were fraudulent. As no-one else was even capable of - +claimed that these experiments were fraudulent. As no-one else was even capable of breeding the creatures involved, they could not be repeated. Kammerer was a communist, and the implicit argument behind his work - was that human beings were perfectable; that some parts of the benefits -of - -humane education and culture would be transmitted. Bateson was again a -Tory, - -though not as politically committed as the other figures discussed. +of humane education and culture would be transmitted. Bateson was again a +Tory, though not as politically committed as the other figures discussed. In these debates it is clear that the protagonists sought ot explain a - phenomenon - in this case evolution - in terms of theories which -supported their \_ +supported their own views of the world. The act of explanation was clearly being used +as a polemic act, to try to pursuade the explainee of the correctness of the +explainers ideological stance\] -» own views of the world. The act of explanation was clearly being used -as a polemic +## Acknowledgments -act, to try to pursuade the explainee of the correctness of the -explainers +I am grateful to Vernon Pratt for helping me clarify the consequences +that this doctrine has for the concepts of 'theory' and 'belief'. lf it is the case that +there is no access to a 'real world', then all statements about the nature of the world are of +equal - undifferentiable - validity (except in so far as some aesthetic criteria +may be applied to them). It remains possible to differentiate between a belief - an +unsupported statement about the nature of the world - and a theory: a statement that the world +has some property as a consequence of certain other properties which it may have. +However, it seems to me that this distinction is of little practical importance. -ideological stance\] +\[**TODO**: Talk about what constitutes a good explanation. Draw on work from -4\. +* Linguistics +* Psychology\] -ll am grateful to Vernon Pratt for helping me clarify the consequences -that this doctrine +## Referenses: -has for the concepts of 'theory' and 'belief'. lf it is the case that -there is no access to a +### Philosophy -'real world', then all statements about the nature of the world are of -equal - +Barwise & Perry, Situations and Attitudes {have this} -undifferentiable - validity (except in so far as some aesthetic criteria -may be applied to +Feyerapend, Against Method {have this} -them). lt remains possible to differentiate between a belief - an -unsupported statement - -about the nature of the world - and a theory: a statement that the world -has some - -property as a consequence of certain other properties which it may have. -However, it - -seems to me that this distinction is of little practical importance. - -Simon Brooke: Notes for a thesis entitled Page : 43 - -li‘ al ,‘! n··n ¢ in L.•-,ni •a |a•1•¤·• •\$¢ - -Linguistics - -Psychology - -Referenses: - -PhHosophy · V - -Barwise, Situations and Attitudes (?) - -Feyerapend, Ageinst Metheg - -ven Fresssen, B Q: The Seientifis Image: Qlerengen Press, Qxfgrg, 1QSQ +ven Fresssen, B Q: The Scientific Image: Clarenden Press, Oxford, 1980 Garfinkel, Forms of Explanation Nagel, The Structure of Science -Pepper, K Qeniesjures and Refujetiens +Pepper, K Conjectures and Refutations {don't have this but might be worth buying} -A Toulmin, The uses of Argument A +A Toulmin, The uses of Argument -Linguistics +### Linguistics -Sperber, Relevance +Sperber, Relevance {have this} -Psychology +### Psychology -Antaki, Lay Explanations of Behaviour +Antaki, C., (1989) ''Lay explanations of behaviour: two psychological cultures'', in *Expert Knowledge and Explanation: The Knowledge-language Interface*, Ellis, C. (ed), Ellis Harwood, London, pp 42-60. + +Antaki, C: Analysing Everyday Explanation Craik, The Nature of Explanation -Draper, S W·, A User Qentreg Qeneep\] ef Explenatien: Alvey Exp SIS 2 +Draper, S W: A User Centred Concept of Explanation: Alvey Exp SIG 2 -O'Me||ey, Q: Applying Studies ef Neturel Dielegge te Human Qempggter -Intereejienz Alvey +O'Melley, Q: Applying Studies of Natural Dialogue to Human Computer Interaction: Alvey Exp SIG 2 -Exp SIQ 2 \_ - -Artificial Intelligence . \~ +### Artificial Intelligence A Goguen, Reasoning and Natural Explanation \` -·k. - -[^1]: Later (p 19), Achinstein refers to 'the audience'. By contrast, he - cites (p 20) an alternative formulation by RJ Mattews in which the - audience is explicitly represented. +---- +[Achinstein 1]: Later (p 19), Achinstein refers to 'the audience'. By contrast, he dcites (p 20) an alternative formulation by RJ Mattews in which the audience is explicitly represented. +[1][OnHylasAndPhilonus.html] Statement of this argument from Berkley's 'Three Dialogues of Hylas and Philonous' diff --git a/doc/Arboretum.md b/doc/Arboretum.md new file mode 100644 index 0000000..27821f4 --- /dev/null +++ b/doc/Arboretum.md @@ -0,0 +1,7 @@ +# Arboretum + +**TODO**: To be scanned from chapter iv of the 21st June 1988 draft. + +![Arboretum screen view showing sample explanations](../img/Arboretum_screen.png) + +*Arboretum screen showing a number of generated explanations. This picture was scanned from a 32 year old acetate slide, apologies for quality* diff --git a/doc/Arboretum_screen.xcf b/doc/Arboretum_screen.xcf new file mode 100644 index 0000000..33dfb99 Binary files /dev/null and b/doc/Arboretum_screen.xcf differ diff --git a/doc/Conception.md b/doc/Conception.md new file mode 100644 index 0000000..fec48d9 --- /dev/null +++ b/doc/Conception.md @@ -0,0 +1,3 @@ +# Conception + +**TODO**: To be scanned from chapter v of the 21st June 1988 draft. diff --git a/doc/History.md b/doc/History.md index c4008d0..de33343 100644 --- a/doc/History.md +++ b/doc/History.md @@ -461,14 +461,17 @@ The application here is to the adjudication of claims to health insurance benef Dear [Name of Claimant] - You are capable of work and there are no special circumstances permitting you to be deemed incapable of work. Although you provided a valid certificate of explanation, this is insufficient unless either there is evidence of contact with the disease or you are a known carrier thereof. + Although physically capable of work you may + nonetheless be deemed incapable of work today. You are + deemed incapable of work for precautionary reasons. You + are deemed incapable of work on precautionary grounds + as you are under medical care, and your doctor has + recommended that you abstain from working. Yours Sincerely [your name] -TODO: this is not a very good Arboretum explanation; I know we did better ones on Widows’ benefit. Check whether I can find a surviving good one, and substitute it. - ### Discussion It will be seen that this is a short, clear, declarative statement in seemingly natural English, which covers all (and only) the relevant points of a complex case. To be fair, the system does not always do this well, but most of its explanations are of this quality. @@ -526,7 +529,11 @@ Although these are all LISP like in form (indeed the assertions themselves are ### Example explanation: - Well, Peter makes less than 750 dollars, and Peter is under 19, and Harry supports Peter so Peter is a dependent of Harry's. Uh Peter makes less than 750 dollars because Peter does not work, and Peter is a dependent of Harry's because Harry provides more than one half of Peter's support. + Well, Peter makes less than 750 dollars, and Peter is under 19, and + Harry supports Peter so Peter is a dependent of Harry's. Uh Peter + makes less than 750 dollars because Peter does not work, and Peter + is a dependent of Harry's because Harry provides more than one half + of Peter's support. I should explain that the application is to the US Federal Income Tax system. This explanation does indeed capture something of the flavour of a natural spoken explanation. Furthermore, it is clearly declarative rather than procedural. However, personally, I find its style rather too informal for textual presentation. I particularly dislike the meaningless 'Uh' which is use to tag the supporting point. diff --git a/doc/OnHylasAndPhilonus.md b/doc/OnHylasAndPhilonus.md new file mode 100644 index 0000000..4c9576e --- /dev/null +++ b/doc/OnHylasAndPhilonus.md @@ -0,0 +1,28 @@ +# On the First Dialogue of Hylas and Philonous + +The argument that our perception of a 'real world' does not prove its +existence is not new, of course. Here is a classic statement of a similar argument from +BerkeIey's *[First Dialogue of Hylas and Philonous](http://www.gutenberg.org/files/4724/4724-h/4724-h.htm)*: + +> Hyl.: Do we not perceive the stars and moon, for example, to be a +A great way off? Is not this, I say, manifest to the senses? I + +> Phil.: Do you not in a dream too perceive those or like objects? + +> Hyl.: I do. + +> Phil.: And have they not then the same appearance of distance? + +> Hyl.: They have. + +> Phil.: But you do not thence conclude the apparitions in a dream to +be without the mind? + +> Hyl.: By no means. + +> Phil.: You ought not therefore to conclude that sensible objects are +without the mind, from their appearance or manner wherein they are +percieved. + +> Hyl.: I acknowledge it. + diff --git a/docs/codox/AgainstTruth.html b/docs/codox/AgainstTruth.html index 8a327e4..76cb571 100644 --- a/docs/codox/AgainstTruth.html +++ b/docs/codox/AgainstTruth.html @@ -1,6 +1,7 @@ -Against Truth

Project

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Against Truth

+Against Truth

Project

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Against Truth

+

Simon Brooke

Hey, what IS truth, man? [Beeblebrox, quoted in [Adams, 1978]]

@@ -9,6 +10,8 @@

This document is in two parts: a statement of a problem, and an account of an attempt to address it. The problem is stated briefly in the first chapter, and fleshed out in the following two with a history of attempts which have been made in the past to address it, and an analysis of what would be needed to solve it.

The second part starts with an account of a system built by the author in collaboration with Peter Mott, describing particularly how the problem was addressed by this system; subsequent chapters will describe the development of a further system, in which the analysis developed in the first section will be applied.

This document deals only with explanation. Issues relating to inference and especially to truth maintenance will undoubtedly be raised as it progresses, but such hares will resolutely not be followed.

+

Note on the quality of the text

+

Much of this text was written between 1986 and 1988 on Xerox 1108 and 1186 workstations, in their native WYSIWYG document system, and printed as hard copy; and some was written on the very first generation of Apple Macintosh computer, and again printed as hard copy. The text here is the consequence of scanning the hard copy and running optical character recognition on the scans. It isn’t perfect. I am proof reading as I go and I hope that it will improve.

Contents

Frontmatter

    @@ -21,6 +24,13 @@
  1. Analysis

Part Two: Into the wild wood

+
    +
  1. Arboretum
    2. +
  2. Conception
    3. +
  3. Reimagining
    4. +
  4. Implementing
    5. +
  5. Experience
    6. +

Endmatter

  1. Errata
    2. diff --git a/docs/codox/Analysis.html b/docs/codox/Analysis.html index 7d5762b..b95b3b7 100644 --- a/docs/codox/Analysis.html +++ b/docs/codox/Analysis.html @@ -1,147 +1,140 @@ -

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    1. Analysis -
        -
      1. -

        Accounts from the Philosophy of Science

        2. -
      -
      2. +Analysis

      Project

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      Analysis

      +

      Accounts from the Philosophy of Science

      +

      (Towards another chapter. What l want to do is: ,

      +
        +
      1. present the DN account, and it’s defenders.
        2. +
      2. present the conventional response
        3. +
      3. present the radical response
        4. +
      4. add some notes of my own, if possible supported by sources, on the polemic nature of explanation)
      -

      <Towards another chapter. What l want to do is: ,

      -

      1] present the DN account, and it’s defenders.

      -

      2] present the conventional response

      -

      3] present the radical response

      -

      4] add some notes of my own, if possible supported by sources, on the polemic nature of explanation>

      This section looks at accounts of explanation culled from the Philosophy of Science. My reason for starting with this field of study is that philosophers in this field have a commitment to express their ideas in strictly formal ways.

      Furthermore, the matter of explanation has always been central to the study [see e.g. van Fraassen 80, p 92; Nagel 61, p 4]. Thus it might be hoped that they would produce a formal account of what constitutes a good argument. While it is not necessarily the case that what can be expressed formally will be computationally tractable, a formal statement of an idea is at least a good start towards computability.

      -

      In fact this link between formal statement and computability is what makes the methodology of Artificial Intelligence such a good tool for the philosopher. Where a formal description can be encoded into a computer language in a computationally tractable manner, the computer programme can be used to evaluate how well the description matches the phenomenon described, simply by observing how well the computer models this phenomenon.

      -
        -
      1. -
          -
        1. Some definitions
          2. -
        2. -
      +

      In fact this link between formal statement and computability is what makes the methodology of Artificial Intelligence such a good tool for the philosopher. Where a formal description can be encoded into a computer language in a computationally tractable manner, the computer programme can be used to evaluate how well the description matches the phenomenon described, simply by observing how well the computer models this phenomenon. I shall pursue this argument in the second half of this thesis.

      +

      Some definitions

      In part of the discussion that follows, it will be necessary to use a shorthand to describe some of the different positions that have been adopted at one time or A another by philosophers of science. Two important positions are realism and A empiricism. The positions are only peripheral to the discussion that follows, but in using them I will generally follow van Fraassen’s usage: by realism, I will mean the view that “…science aims to find a true description of unobservable processes that explain the observable ones…” [van Fraassen ’8O page 3] This view holds that a theory is only adequate if it’s description of the world is correct in the finest detail.

      By contrast, by empiricism I shall mean the view that a theory is adequate provided it gives a correct account of the observable phenomena. Any underlying mechanism may be postulated, provided that it accounts for the observable behaviour.

      I shall also use another term from the same debate - positivism. I shall not use this in the precise sense that van Frassen gives it, but in a looser, more colloquial sense, to define that group of doctrines (including all realist and most empiricist doctrines) which hold that there is a real world, and that that real world is accurately reflected in our perceptions.

      -
        -
      1. -
          -
        1. Aristotle to Nagel
          2. -
        2. -
      +

      Aristotle to Nagel

      The Philosophy of Science has had the development of an account of explanation as one of its central projects since Aristotle. Aristotle’s account of explanation was broadly that an explanation was an argument which had the explicandum as its consequent. As, to Aristotle, arguments should be constructed as syllogisms or chains of syllogisms, the correct explanation in response to ‘How do you know that Socrates is mortal?’ would be:

      -

      Socrates is a man;

      -

      All men are mortal;

      -

      Therefore Socrates is mortal.

      -

      [a syllogism of the mood barbara ]

      +
      Socrates is a man;
+All men are mortal;
+Therefore Socrates is mortal.
+
      +

      a syllogism of the mood barbara

      This account, which has become known as the ‘hypothetico-deductive’ or ‘deductive-nomological’ account of explanation, has effectively been the dominant account ever since. The classic statement of this account in the present century is probably that given by Hempel [Hempel, 65]. Ernest Nagel [Nagel, 61] attempted to go beyond this to a more general account of explanation, but he included the deductive-nomological form as the first of the four types of explanation which he describes.

      Nagel claims, rather baldly, that “Explanations are answers to the question ‘Why?’”, but later goes on to note “…the important point that even answers to the limited class of questions introduced by ‘Why’ are not all of the same kind.” His four types of explanation are: deductive explanations, probabilistic explanations, functional or teleological explanations, and genetic explanations.

      -
        -
      1. -
          -
        1. -
            -
          1. Deductive explanations
            2. -
          2. -
        2. -
      +

      Deductive explanations

      Nagel’s deductive explanations have the formal structure of a deductive argument, rather in the manner of a logical proof. This is essentially the deductive nomological explanation. In the case of the explanation of singularities, it fits neatly with the Toulmin [below] - or indeed the sylogistic - form of argument: data, plus principle, imply conclusion:

      -

      “It is evident that at least one of the premises in a deductive explanation of a singular explicandum must be a universal law…” (page 31)

      -

      “… a deductive scientific explanation, whose explicandum is the occurance of some event or the possession of some property by a given object, must satisfy two logical conditions. The premises must include at least one universal law, whose inclusion is essential to the deduction of the explicandum. And the premises must also contain a suitable number of initial conditions.” (page 32)

      +
      +

      “It is evident that at least one of the premises in a deductive explanation of a singular explicandum must be a universal law…” (page 31)

      +

      “… a deductive scientific explanation, whose explicandum is the occurance of some event or the possession of some property by a given object, must satisfy two logical conditions. The premises must include at least one universal law, whose inclusion is essential to the deduction of the explicandum. And the premises must also contain a suitable number of initial conditions.” (page 32)

      +

      In the case of the explanation of scientific laws, however:

      -

      “…all the premises are universal statements; (and) there is more than one premise, each of which is essential in the derivation of the exp1icandum…” (page 34)

      -

      “…at least one of the premises must be ‘more general’ than the law being explained.” (page 37)

      +
      +

      “…all the premises are universal statements; (and) there is more than one premise, each of which is essential in the derivation of the exp1icandum…” (page 34)

      +

      “…at least one of the premises must be ‘more general’ than the law being explained.” (page 37)

      +

      The notion of ‘more general’ is discussed at length, and is defined as follows:

      -

      "Let L~1~ be a law (or a set of laws and theories constituting some science such as physics), and let ‘P~1~’ ‘P~2~’ … , ‘P~n~’ be a set of ‘primitive’ predicates in terms of which the predicates occuring in L~1~ are in some sense definable. (For the sake of simplicity, and without any loss of the generality of statement, we shall assume that the predicates are all adjectives or ‘one-place’ predicates such as ‘rigid’ or ‘heavy’ …. ) Similarly, let ‘Q~1~’ ‘Q~2~’ … , ‘Q~n~’ be the corresponding set of primitives for a law L~2~. Finally, let K be a class of objects, each of which can be significantly (or meaningfully) characterised, whether truly or falsely, by the predicates of either set …. We shall also say that an object in K satisfies a law L ‘non-vacuously’ only if the object actually possesses the various traits mentioned in the law and, moreover, the traits do stand to each other in the relations asserted by the law…

      -

      We now assume the following conditions: (1) Some (and perhaps all) of the predicates in the first set occur in the second, but some predicates in the second set do not occur in the first set. (2) Every object in K has at least one P-property, that is, a property designated by a predicate in the first set. (3) There is a non-empty subclass A of objects in K possessing only P-properties. (4) There is a non-empty subclass A of objects in K each of which possesses at least one Q- property that is not a P-property. …. (5) There is a non-empty (but not necessarily proper) subclass B of objects in K each of which satisfies L~1~ non-vacuously, and such that some objects in B belong to A while others belong to A. …. (6) There is a non-empty subclass C of objects in A for which L~2~ holds non-vacuously, and such that some (and perhaps all) of the objects in C also belong to B ….. When these six conditions are fulfilled, L~1~ may be said to be more general in K than L~2~." (pp 40- 41).

      -

      [my transcription differs from the original in. that where Nagel uses a character formed of an upper case letter A with a bar over it, I have used a struck-through A; and, more significantly, Nagel uses an unbarred A in condition 4. From my understanding of the text I have assumed this is a misprint, and have substituted an struck-through A]

      +
      +

      "Let L~1~ be a law (or a set of laws and theories constituting some science such as physics), and let ‘P~1~’ ‘P~2~’ … , ‘P~n~’ be a set of ‘primitive’ predicates in terms of which the predicates occuring in L~1~ are in some sense definable. (For the sake of simplicity, and without any loss of the generality of statement, we shall assume that the predicates are all adjectives or ‘one-place’ predicates such as ‘rigid’ or ‘heavy’ …. ) Similarly, let ‘Q~1~’ ‘Q~2~’ … , ‘Q~n~’ be the corresponding set of primitives for a law L~2~. Finally, let K be a class of objects, each of which can be significantly (or meaningfully) characterised, whether truly or falsely, by the predicates of either set …. We shall also say that an object in K satisfies a law L ‘non-vacuously’ only if the object actually possesses the various traits mentioned in the law and, moreover, the traits do stand to each other in the relations asserted by the law…

      +

      We now assume the following conditions: (1) Some (and perhaps all) of the predicates in the first set occur in the second, but some predicates in the second set do not occur in the first set. (2) Every object in K has at least one P-property, that is, a property designated by a predicate in the first set. (3) There is a non-empty subclass A of objects in K possessing only P-properties. (4) There is a non-empty subclass A of objects in K each of which possesses at least one Q- property that is not a P-property. …. (5) There is a non-empty (but not necessarily proper) subclass B of objects in K each of which satisfies L~1~ non-vacuously, and such that some objects in B belong to A while others belong to A. …. (6) There is a non-empty subclass C of objects in A for which L~2~ holds non-vacuously, and such that some (and perhaps all) of the objects in C also belong to B ….. When these six conditions are fulfilled, L~1~ may be said to be more general in K than L~2~." (pp 40- 41).

      +
      +

      (my transcription differs from the original in. that where Nagel uses a character formed of an upper case letter A with a bar over it, I have used a struck-through A; and, more significantly, Nagel uses an unbarred A in condition 4. From my understanding of the text I have assumed this is a misprint, and have substituted an struck-through A.) TODO check typography as processed by Markdown!

      Deductive explanations, as stated above, have the general form of the syllogism Barbara. However, Nagel adds a condition: while all the clauses of Barbara are universally quantified, one of the premisses must be more general than the conclusion to qualify as an explanation of it. In the case of an explanation about a singularity, it is trivial that the ‘universal law’ is more general than the ‘initial conditions’; in the case of explanations of generalities, Nagel has gone to lengths to assert this condition.

      Nagel rejects as too strong the Aristotelian requirements that the premises of a deductive explanation should not only be true but should be known to be true, and that they should be ‘better known’ than the explicandum. He observes that the ‘universal premises’ which are subsumed into ‘scientific laws’ are true. Instead he suplies the weaker condition that:

      -

      “…the explanatory premises be compatible with established empirical facts and be in addition ‘adequately supported’ (or ‘made probable’) by evidence based on data other than the observational data upon which the acceptance of the explicandum is based.” (p 43)

      -

      “In maintaining that the premises in an explanation must be ‘better known’ than the explicandum, Aristotle was thus simply making explicit his conception of science. This conception is true of nothing that can be identified as part of the asserted content of modern empirical science,” (p 45)

      -
        -
      1. -
          -
        1. -
            -
          1. Probabilistic explanations
            2. -
          2. -
        2. -
      -

      Nagel’s second category, probabilistic explanations, depend not on formal

      -

      implication of the explicandum by the premises contained within the explanation,

      -

      but on some ‘statistical reregularity’ taking the general form:

      -

      Most x are y

      -

      a is x

      -

      => it is probable that a is y

      +
      +

      “…the explanatory premises be compatible with established empirical facts and be in addition ‘adequately supported’ (or ‘made probable’) by evidence based on data other than the observational data upon which the acceptance of the explicandum is based.” (p 43)

      +

      “In maintaining that the premises in an explanation must be ‘better known’ than the explicandum, Aristotle was thus simply making explicit his conception of science. This conception is true of nothing that can be identified as part of the asserted content of modern empirical science,” (p 45)

      +
      +

      Probabilistic explanations

      +

      Nagel’s second category, probabilistic explanations, depend not on formal implication of the explicandum by the premises contained within the explanation, but on some ‘statistical reregularity’ taking the general form:

      +
      Most x are y
+a is x
+=> it is probable that a is y
+

      Nagel notes that:

      -

      “It is still an unsettled question whether an explanation must contain a statistical assumption in order to be a probabilistic one, or whether nonstatistical premises may make an explicandum ‘probable’ in some nonstatistical sense of the word.” (p 23)

      -

      such explanations can be expressed in the Toulmin scheme (see below); but as syllogisms have the general form IAA, which is not valid.

      +
      +

      “It is still an unsettled question whether an explanation must contain a statistical assumption in order to be a probabilistic one, or whether nonstatistical premises may make an explicandum ‘probable’ in some nonstatistical sense of the word.” (p 23)

      +
      +

      Such explanations can be expressed in the Toulmin scheme (see below); but as syllogisms have the general form IAA, which is not valid.

      These two types are the models of scientific explanation that Nagel describes; but he also describes two other categories. These are explanation types which appear in natural conversation, and in law and the humanities.

      -
        -
      1. -
          -
        1. -
            -
          1. Functional (teleological) explanations
            2. -
          2. -
        2. -
      +

      Functional (teleological) explanations

      Functional (teleological) explanations are explanations which refer to the supposed purpose of the explicandum:

      -

      “lt is characteristic of functional explanations that they employ such typical locutions as ‘in order that’, ‘for the sake of’ and the like.” (p 24)

      +
      +

      “lt is characteristic of functional explanations that they employ such typical locutions as ‘in order that’, ‘for the sake of’ and the like.” (p 24)

      +

      There are two sub classes of functional explanation. One is the explanation of a particular instance or occurrence: .. .

      -

      ‘I caught hold of the branch so that I would not fall.’

      +
      'I caught hold of the branch so that I would not fall.'
+

      whereas the other explains something which occurs in all instances of a particular class:

      -

      ‘Birds have wings so that they can fly.’

      -
        -
      1. -
          -
        1. -
            -
          1. Genetic explanations
            2. -
          2. -
        2. -
      +
      'Birds have wings so that they can fly.'
+
      +

      Genetic explanations

      Genetic explanations seek to explain why something is the way it is by explaining how it came to be this way:

      -

      ‘My arm is broken because I fell out of a tree’

      -

      ‘Penguins have wings because they evolved from birds which could fly’

      +
      'My arm is broken because I fell out of a tree'
+
+'Penguins have wings because they evolved from birds which could fly'
+

      It is clear that these are categories where the explanations are neither necessary nor sufficient causes of the explicanda; you don’t have to fall out of a tree to break your arm, and you can break it without falling out. Likewise, there may have been other ways of not falling than catching hold of a branch, and catching hold of a branch may not prevent a fall.

      But there are statistical probabilities (not necessarily high) that catching the branch will prevent the fall, and that a fall will lead to a broken arm.

      -

      “It is therefore a reasonable conclusion that genetic explanations are by and large probabilistic.” (p 26)

      -
        -
      1. -
          -
        1. The radical critics
          2. -
        2. -
      +
      +

      “It is therefore a reasonable conclusion that genetic explanations are by and large probabilistic.” (p 26)

      +
      +

      The radical critics

      These conventional arguments in the philosophy of science were dramatically disturbed in the 1960s by radical philosophers like Thomas Kuhn [Kuhn, 62] and Paul Feyerabend [Feyerabend, 78; and passim]. Their attack was not directed specifically at accounts of explanation, but at the empiricist and realist views of science as such - which is to say the view – implicit in both – that we can directly access the external world in order to gain knowledge which would support a theory.

      The damage to the account of explanation was almost incidental in this process. It was fatal, however; the consensual view of explanation did not survive. A number of accounts of explanation have developed since then; dissapointingly, these all seem to be timid and conservative, attempting to preserve a view of science which is no longer tenable. Following (but not, as far as I am aware, prior to) the radicals onslaught, writers on the philosophy of science developed a formidable arsenal of objections to the deductive-nomological account. I cite here a few drawn from [Korner 75]:

      -

      Achinstein, in his note The Object of Explanation, gives some ‘standard counler—examp|es’:

      -

      "1] We see a fire engine which is black and demand an explanation. Here is one that satisfies the D-N model:

      -

      This fire engine is the same colour as that crow.

      -

      All crows are black.

      -

      =>This fire engine is black.

      -

      2] A bridge collapses and we demand an explanation, Here is one that satisfies the D-N model:

      -

      An engineer with years of training and experience examined the bridge and said it would collapse.

      -

      Whenever an engineer with years of training and experience examines a bridge and says it will collapse, it does.

      -

      => The bridge collapsed.

      -

      These are unacceptable as explanations …. " (page 35)

      +

      Achinstein, in his note The Object of Explanation, gives some ‘standard counler-examp|es’:

      +
      +

      "1. We see a fire engine which is black and demand an explanation. Here is one that satisfies the D-N model:

      +
      +

      This fire engine is the same colour as that crow.

      +

      All crows are black.

      +

      =>This fire engine is black.

      +
      +

      2. A bridge collapses and we demand an explanation. Here is one that satisfies the D-N model:

      +
      +

      An engineer with years of training and experience examined the bridge and said it would collapse.

      +

      Whenever an engineer with years of training and experience examines a bridge and says it will collapse, it does.

      +

      => The bridge collapsed.

      +
      +

      These are unacceptable as explanations …. " (page 35)

      +

      Hesse, in her rejoinder to Achinstein, writes:

      -

      “… there are by now at least three widely accepted general consequences of the ensuing debate which are enough to show that this model is by no means to be taken as the ‘standard model of explanation’.

      -

      These are:

      -

      (i) It has grave shortcomings as an explication of the structure of explanation in natural science itself. (ii) The question of whether it usefully applies to explanation in history, psychology, and the social sciences is a matter of current controversy. (iii) The question of whether any model applying to the natural sciences is adequate also for these human sciences is also highly controversial." (page 46, Hesse’s emphasis)

      +
      +

      “… there are by now at least three widely accepted general consequences of the ensuing debate which are enough to show that this model is by no means to be taken as the ‘standard model of explanation’.

      +

      These are:

      +

      (i) It has grave shortcomings as an explication of the structure of explanation in natural science itself.

      +

      (ii) The question of whether it usefully applies to explanation in history, psychology, and the social sciences is a matter of current controversy.

      +

      (iii) The question of whether any model applying to the natural sciences is adequate also for these human sciences is also highly controversial." (page 46, Hesse’s emphasis)

      +

      and finally, Salmon, in a piece entitled Theoretical Explanation, argues:

      -

      "… contra Hempel and many others - that an explanation [of a particular event] is not ‘an argument to the effect that the event to be explained was to be expected by reason of certain explanatory facts’…

      -

      In addition, I have claimed that the so-called deductive- nomological model of explanation of particular events is incorrect. It is not merely that there are explanandum events which seem explainable only inductively or statistically… There are also cases – such as the man who takes his wife’s birth control pills and avoids pregnancy – in which an obviously defective explanation fulfills the conditions for deductive-nomological explanation. (pp 118-119; the embedded quote is from Hempel, Explanation in Science and in History, in Colodny, ed, Frontiers of Science and Philosophy, University of Pittsburgh Press, Pittsburgh, 1962. The italics are Salmon’s. This birth control example is also mentioned in for example van Frassen 1980)

      +
      +

      "… contra Hempel and many others - that an explanation [of a particular event] is not ‘an argument to the effect that the event to be explained was to be expected by reason of certain explanatory facts’…

      +

      In addition, I have claimed that the so-called deductive- nomological model of explanation of particular events is incorrect. It is not merely that there are explanandum events which seem explainable only inductively or statistically… There are also cases – such as the man who takes his wife’s birth control pills and avoids pregnancy – in which an obviously defective explanation fulfills the conditions for deductive-nomological explanation. (pp 118-119; the embedded quote is from Hempel, Explanation in Science and in History, in Colodny, ed, Frontiers of Science and Philosophy, University of Pittsburgh Press, Pittsburgh, 1962. The italics are Salmon’s. This birth control example is also mentioned in for example van Frassen 1980)

      +

      [Here insert some detailed analysis of Feyerabend’s position, and passing reference to Lakatos and Kuhn]

      -
        -
      1. -
          -
        1. Achinstein
          2. -
        2. -
      +

      van Fraassen

      +

      Another philosopher who has attracted attention with his work on explanation in recent years is Bas van Fraassen. His work seems directed, however, not primarily at providing better accounts of explanation, so much as at defending the empirical view of science from the realist critics of it - surely, at this late date, a redundant activity. The work is marred, in my opinion, by intellectually dishonest treatment of the radicals, to whom van Fraassen has no honest response.

      +

      van Fraassen’s response to the radicals

      +

      van Fraassen published his ‘the Scientific Image’ in 1980, in the age of Feyerabend and Kuhn. He mentions both these authors twice, and is clearly familiar with their theses, describing Feyerabend’s work as ‘well known’ (page 14), and paraphrasing one of Feyerabend’s central points (although without acknowledging it):

      +
      +

      “… one theory says that there are electrons, and the other says that there may not be. Even if the observable phenomena are as Rutherford says, the unobservable may be different. However, the positivists would say, if you argue that way, you automatically become a prey to scepticism. You will have to admit that there are possibilities that you cannot prove or disprove by experiment, and so you will have to say we cannot know what the world is like. Worse; you will have no reason to reject any number of outlandish possibilities; demons, witchcraft, hidden powers contirbuting to fantastic ends.” (page 35, my emphasis)

      +
      +

      Well yes, precisely. And although it is possible that the positivists would say it, Feyerabend did say it, repeatedly; and the choice of words seems to me to betray a consciousness of this [see for example Feyerabend, 81, vol 1, foot of page 196 - which other evidence (below) shows us van Fraassen was familiar with]. But the only time van Fraassen addresses an argument of Feyerabend’s directly, he dismisses it as ‘…a totally false issue…’ (page 93). Let us look a little at the context for this.

      +

      van Fraassen is discussing the centrality of explanation to science, citing - and accepting - Nagel’s strong claim [Nagel 61, page 4], and using incidentally the same passage from Nagel as Feyerabend had used in his earlier critique of this work [Feyerabend 81, page 52; this paper originally published in BJPS vol 16, 1964] to illustrate this. He claims that Nagel’s view does not entail realism, but will equally support an empiricist view. He now claims that Feyerabend has advanced the ‘..totally false..’ argument that, in his paraphrase:

      +
      +

      ’…only Realism is a philosophy that stimulates scientific enquiry; anti-realism hampers it." [page 93]

      +
      +

      This is a position that Feyerabend advanced? Really? Feyerabend whose central thesis might be summed up in his phrase “The only principle that does not inhibit progress is: anything goes.” [Feyerabend 75, p10: F’s emphasis]. van Fraassen refers us to Feyerabend’s paper [in Feyerabend 81 vol 1]. What Feyerabend in fact says (forgive me if I quote at length) is:

      +
      +

      “To sum up: the issue between realism and instrumentalism has A many facets….. There are arguments for instrumentalism which concern specific theories such as the quantum theory or the heliocentric hypothesis and which are based on specific facts and well confirmed theories. It was shown that to demand realism in these cases amounts to demanding support for implausible conjectures which possess no independent empirical support and which are inconsistent with facts and well confirmed theories. It was also shown that this is a plausible demand which immediately follows from the principle of testability. Hence realism is preferable to instrumentalism even in these most difficult cases.” [Feyerabend 81 vol 1 pp 201-2; Feyerabend’s emphasis.]

      +
      +

      ‘Realism is preferable to instrumentalism’. That is a very different (and far weaker) claim than ‘only Realism stimulates scientific enquiry’. So the totally false issue is of van Fraassen’s own devising, and has nothing to do with Feyerabend.

      +

      I have gone on at some length about van Fraassen’s slight (and slighting) mention of Feyerabend. Why? Well, because van Fraassen, continuing the now moribund debate between realism and empiricism in order to defend the latter, addresses Feyerabend’s criticisms of neither doctrine. This seems an extraordinary ommission.

      +

      <Here insert some stuff about van Fs account of explanation…>

      +

      Achinstein

      One of the first attempts to recover an account of explanation from this mess is that of Achinstein [Achinstein 83]. Achinstein distinguishes between the act of explaining, which is an utterance, and the explanation, which is the product of the act. This act must take place in an appropriate context.

      His project is to answer three questions: .

        @@ -149,547 +142,217 @@
      1. What is the product of an explaining act?
      2. How should explanations be evaluated?
      - -
        -
      1. -
          -
        1. -
            -
          1. ‘Explaining acts’
            2. -
          2. -
        2. -
      +

      ‘Explaining acts’

      Achinstein claims that ‘explaining acts’ have a period, and a completion point.

      -

      ‘John was explaining why x’

      -

      ‘John explained x’

      +
      'John was explaining why x'
+
+'John explained x'
+

      The latter form implies a completion has occurred.

      An explanation has not occurred until the act of explanation has occurred. For John to have explained why x, it is not sufficient that he knew why x.

      ‘Explaining’ is illocutionary [see Austin, how to do things with words]; it is done in an appropriate context. Out of such a context, the same statement would be an equivalent perlocutary act: ‘enlightening’, ‘getting <the auditor> to understand’.

      The intention of an explaining act must be to engender understanding of the explicanda. Achinstein does not state, but may be taken to imply, that for such an act to take place there must (at any rate in the mind of the explainer) be some explainee or auditor, in whose mind understanding is to be engendered[^1].

      -

      "The first condition expresses what I take to be a fundamental relationship between explaining and understanding. It is that S explains q by uttering u only if

      -

      (1) S utters u with the intention that his utterance of u render q understandable."(Page ??)

      +
      +

      "The first condition expresses what I take to be a fundamental relationship between explaining and understanding. It is that S explains q by uttering u only if

      +
        +
      1. S utters u with the intention that his utterance of u render q understandable."(Page ??)
        2. +
      +

      Under this account it is impossible to explain something by accident – a rather over strict condition, l think.

      Achinstein also claims that it is neccesary that the utterance produced by the explaining act must be (at least believed to be) a correct account:

      -

      "(2) S believes that u expresses a proposition that is a correct answer to Q…

      +
      +

      "2. S believes that u expresses a proposition that is a correct answer to Q…

      +

      Often people will present hints, clues, or instructions which do not themselves answer the questions… Some hints, no doubt, border on being answers to the question. But in those cases where they do not, it is not completely appropriate to speak of explaining."(p 17)

      Thus explanation by analogy is no explanation; again, this seems a very strong condition. Yet Achinstein goes on to make this even stronger by the assertion that the proposition expressed by u is itself a complete answer to Q:

      -

      “(3) S utters u with the intention that his utterance render q understandable by producing the knowledge, of the proposition expressed by u, that it is a correct answer to Q.”(p 18)

      +
      +

      “3. S utters u with the intention that his utterance render q understandable by producing the knowledge, of the proposition expressed by u, that it is a correct answer to Q.”(p 18)

      +

      Atchinstein goes on to say that ‘explain’ can be used in two senses: a loose sense, in which any situation fulfilling the above contains an explanation; and a more restricted sense, which will “cover only correct explainings”. He does not describe how these may be differentiated, however.

      -
        -
      1. -
          -
        1. -
            -
          1. Understanding
            2. -
          2. -
        2. -
      +

      Understanding

      If explaining is to be seen as an act directed at engendering understanding, some account of what is meant by ‘understanding’ must be supplied. Achinstein asserts that:

      "One understands q only if one knows a correct answer to Q which one knows to be correct (sic)… we can say that a necessary condition for the truth of sentences of the form ‘At understands q’ is

      -

      (1) (£x)(A knows of x that it is a correct answer to Q)" (p 23 - 4)

      +
      +

      (∀x)(A knows of x that it is a correct answer to Q)" (p 23 - 4)

      +

      Achinstein’s essential problem is quite simple to express: he wants to say that one doesn’t understand something until one not only knows a proposition which expresses the reason for it, and knows that this proposition does in fact express the ‘correct’ reason, but also has internalised this proposition.

      -
        -
      1. -
          -
        1. -
            -
          1. -
              -
            1. ‘Content-giving Propositions’
              2. -
            2. -
          2. -
        2. -
      +

      ‘Content-giving Propositions’

      Achinstein identifies a class of nouns which he describes as ‘content-giving’, such as ‘explanation’, ‘meaning’, ‘fact’, ‘reason’. He then defines a class of propositions, constructed using such nouns and the verb to be, which he calls ‘content-giving propositions’. These take roughly the form:

      -

      ‘the <cg-noun> {that | of | for} <proposition x> is <proposition y>.’

      +
      'the <cg-noun> {that | of | for} <proposition x> is
+<proposition y>'
+

      Achinstein now expands his definition of understanding to:

      -

      “(∃p)(A knows of p that it is a correct answer to Q, and p is a complete content-giving proposition with respect to Q)” (p 42) .

      +
      +

      “(∃p)(A knows of p that it is a correct answer to Q, and p is a complete content-giving proposition with respect to Q)” (p 42) .

      +

      Achinstein examines a number or accounts of the epistemic nature of an explanation, largely to use them as Aunt Sallies, before presenting his preferred account. He examines first explanation considered as sentence and as proposition.

      These are rejected for reasons which appear to me quite strange. Achinstein has trouble with the idea that two sentences can be differently constructed but have the same meaning. E.g.:

      -

      “…since sentence (1) ≠ sentence (2), the explanation of Bill’s stomach ache given by Dr. _Smith ≠ the explanation of Bill’s stomach ache given by Dr. Robinson, which seems unsatisfactory. Intuitively, both doctors have given the same explanation…”(p 76)

      +
      +

      “…since sentence (1) ≠ sentence (2), the explanation of Bill’s stomach ache given by Dr. Smith ≠ the explanation of Bill’s stomach ache given by Dr. Robinson, which seems unsatisfactory. Intuitively, both doctors have given the same explanation…”(p 76)

      +

      What Achinstein dearly wants is some Leibnitzian language in which he can express the semantic content of the sentences. Not having one, it is not sufficient for him to posit that such a thing must exist; so he claims that behind every sentence there is a (presumably unique) proposition, in English. Thus:

      -

      “Since sentences (1) and (2) express the same proposition we can conclude that the explanations given by the doctors are the same.”(p 76)

      +
      +

      “Since sentences (1) and (2) express the same proposition we can conclude that the explanations given by the doctors are the same.”(p 76)

      +

      For evidence that the proposition is considered to be unique, see the bizarre argument presented as the ’Locutionary Force Problem’ on p 77. ln this (by my reading) he claims that:

      ix if the product of an explanation is a proposition, and it is possible to produce, as separate acts of explanation and of criticism, utterances which map onto the same proposition, then that proposition is at once a criticism and an explanation, which is absurd. Therefore the product of an explanation cannot be a proposition.

      -

      l doubt whether this argument has meaning, let alone force. ln this and other arguments, Achinstein seems to confound operations which would be legitimate on some formal grammar with what it is possible to do with natural language.

      +

      I doubt whether this argument has meaning, let alone force. ln this and other arguments, Achinstein seems to confound operations which would be legitimate on some formal grammar with what it is possible to do with natural language.

      His view that propositions are unique is made more difficult to maintain by his apparent identification of the propositions themselves with the sequence of symbols used to represent it. For a statement of the view that sequences of symbols are efficient (i.e. that they may have many differing meanings), see e.g. [Barwise and Perry 86, p S2]; ,

      -

      He also has trouble with emphasis shifts in propositions which are

      -

      represented by the same sequence of word-tokens, which he resolves by the

      -

      concept of ‘e-sentences’ - sentences with additional flagging to indicate the

      -

      central phrase, so that:

      -

      "(7) the e-sentence ‘Bill ate spoiled meat on Tuesday’ is not

      -

      identical with

      -

      8 (8) the e-sentence ‘Bill ate spoiled meat on Tuesday"’ (p 80)

      -

      He next considers the deductive-nomological view - the view that an

      -

      ’ explanation is an argument.

      -

      Achinstein argues that the form of the deductive nomological explanation can

      -

      be seen as an ordered pair <conjunction of premises, conclusion>. This view is

      -

      dismissed for reasons analogous to those above.

      -

      Explanation as ordered pair

      -

      Having considered, and dismissed, the preceding accounts of explanation, A.

      -

      _ now proposes that explanation should be considered to be an ordered pair <x, y>

      -

      s.t.: .

      -

      "’The explanation of q given by S denotes (x; y) if and only if

      -

      (i) Q is a content-question;

      -

      (ii) x is a complete content-giving proposition with respect to Q;

      -

      (iii) y = explaining q; `

      -

      (iv) (£a)(£u)[a is an act in which S explained q by uttering u ->

      -

      (r)(r is associated with with a;r=x)]. (i.e., x is the one and only

      -

      A proposition associated with every act in which S explained q by `

      -

      uttering something.)"(p 87) _

      +

      He also has trouble with emphasis shifts in propositions which are represented by the same sequence of word-tokens, which he resolves by the concept of ‘e-sentences’ - sentences with additional flagging to indicate the central phrase, so that:

      +
      +

      "(7) the e-sentence ‘Bill ate spoiled meat on Tuesday’ is not identical with (8) the e-sentence ‘Bill ate spoiled meat on Tuesday"’ (p 80)

      +
      +

      He next considers the deductive-nomological view - the view that an explanation is an argument.

      +

      Achinstein argues that the form of the deductive nomological explanation can be seen as an ordered pair <conjunction of premises, conclusion>. This view is dismissed for reasons analogous to those above.

      +

      Explanation as ordered pair

      +

      Having considered, and dismissed, the preceding accounts of explanation, Achinstein now proposes that explanation should be considered to be an ordered pair <x, y>

      +

      s.t.:

      +
      +

      "The explanation of q given by S denotes (x; y) if and only if

      +

      (i) Q is a content-question; (ii) x is a complete content-giving proposition with respect to Q; (iii) y = explaining q; (iv) (£a)(£u)[a is an act in which S explained q by uttering u -> (r)(r is associated with with a;r=x)]. (i.e., x is the one and only A proposition associated with every act in which S explained q by `uttering something.)"(p 87)

      +

      What this appears to boil down to is this:

      -

      Achinstein believes any given concatenation of symbols representing a

      -

      " proposition to be identical with that proposition; and that any proposition is

      -

      uniquel. ·

      +

      Achinstein believes any given concatenation of symbols representing a proposition to be identical with that proposition; and that any proposition is unique.

      Thus each and every occurance of this sequence of symbols is the same thing.

      Yet he believes, as shown above, that it is impossible for (e.g.) an explanation to

      -

      lln fact, Achinstein’s claim is even stronger than this, for he believes that there is some

      -

      proposition ‘underneath’ each sentence; thus, potentially, many sentences may map onto

      -

      the same proposition, and consequently all these sentences may be treated as being

      -

      identical (l).

      -

      Simon Brooke: Notes for a thesis entitled Page : 34

      -

      Meghaniseq Inference and Explanation Draught dated ; 2]{§[§§

      -

      be ‘the same thing’ as (e.g.) a criticism. So it is impossible for an explanation to

      -

      be identical with an occurance of a sequence of symbols.

      -

      Thus an ordered pair must be constructed, in which the symbol-sequence is

      -

      linked with another symbol sequence which represents a reference to the

      -

      question which was asked.

      +

      In fact, Achinstein’s claim is even stronger than this, for he believes that there is some proposition ‘underneath’ each sentence; thus, potentially, many sentences may map onto the same proposition, and consequently all these sentences may be treated as being identical (l).

      +

      be ‘the same thing’ as (e.g.) a criticism. So it is impossible for an explanation to be identical with an occurance of a sequence of symbols.

      +

      Thus an ordered pair must be constructed, in which the symbol-sequence is linked with another symbol sequence which represents a reference to the question which was asked.

      Note that q, the question, is also a sequence of symbols; so that a pair:

      -

      <[aI| plants are green]; [answering: “why is this grass green”]> .

      -

      is unique, and is always the same explanation. Therefore (since Achinstein’S4» gp

      -

      schema makes no mention of an auditor) it is always either a good explanation or

      -

      a bad one, regardless of whether the question was asked by a three year old child

      -

      or a plant physiologist.

      +

      <[all plants are green]; [answering: “why is this grass green”]> .

      +

      is unique, and is always the same explanation. Therefore (since Achinstein’s schema makes no mention of an auditor) it is always either a good explanation or always a bad one, regardless of whether the question was asked by a three year old child or a plant physiologist.

      I would like to return the readers attention to Achinstein’s claim that:

      -

      "One understands q only if one knows a correct answer to Q which

      -

      one knows to be correct " [p 23, my emphasis]

      -

      and goes on to clarify that, by this, he implies ‘…a de re sense of knowing.’ as

      -

      " The use of ‘correct’ here is the problem. It appears to imply that one knows that

      -

      the answer which one knows maps in some unproblematic way onto something

      -

      real in the external world. Thus Achinstein, too, falls into the trap sprung by the

      -

      radicals. ln the absence of some definition of what is to be understood by

      -

      ‘correct’, these definitions are simply meaningless.

      -

      ·; ; —• ·_ gt g J; rg FQ :r. ns .· efbr ¢’<—¤ · S = " . ~w’ ll’

      -

      9 (v x ~ J · ’Q~ k. , l 6 4 4

      -

      P7 » %‘· both orde al ;/ an ns (parables s ve.

      -

      ‘ This account does not address many of the facets of common sense explanation.

      -

      It has nothing to say about the amount of detail contained in an explanation. It has

      -

      nothing to say about the need to express an explanation in terms of an account of

      -

      the world which is accessible to the auditor. lt fails to account for the possibility

      -

      of explanation by analogy, or of unintentional explanation.

      -

      It appears that Achinstein’s motivation in producing a new account has less to

      -

      do with addressing these real world problems than with overcoming such

      -

      philosophical puzzles as the Paradox of the Ravens; so his account takes us no

      -

      nearer to providing a model which will support the construction of better

      -

      common sense explanations. 5

      +
      +

      “One understands q only if one knows a correct answer to Q which one knows to be correct ” [p 23, my emphasis]

      +
      +

      and goes on to clarify that, by this, he implies ‘…a de re sense of knowing.’

      +

      The use of ‘correct’ here is the problem. It appears to imply that one knows that the answer which one knows maps in some unproblematic way onto something real in the external world. Thus Achinstein, too, falls into the trap sprung by the radicals. In the absence of some definition of what is to be understood by ‘correct’, these definitions are simply meaningless.

      +

      This account does not address many of the facets of common sense explanation.

      +

      It has nothing to say about the amount of detail contained in an explanation. It has nothing to say about the need to express an explanation in terms of an account of the world which is accessible to the auditor. lt fails to account for the possibility of explanation by analogy, or of unintentional explanation.

      +

      It appears that Achinstein’s motivation in producing a new account has less to do with addressing these real world problems than with overcoming such philosophical puzzles as the Paradox of the Ravens; so his account takes us no nearer to providing a model which will support the construction of better common sense explanations. 5

      A [ mh L/Go/w%` \

      ` Eegozi

      -

      van Fraassen Arclltuqrfélv

      -

      _ Another philosopher who has attracted attention with his work on explanation

      -

      in recent years is Bas van Fraassen. His work seems MNMW directed, trbeislz

      -

      however, not primarily at providing better accounts of explanation, so much as

      -

      at defending the empirical view of science from the realist critics of it - surely,

      -

      at this late date, a redundant activity. The work is marred, in my opinion, by

      -

      intellectually dishonest treatment of the radicals, to whom van Fraassen has no

      -

      honest response.

      -

      van Fraassen’s response to the radicals

      -

      van Fraassen published his ‘the Scientific Image’ in 1980, in the age of

      -

      Feyerabend and Kuhn. He mentions both these authors twice, and is clearly

      -

      familiar with their theses, describing Feyerabend’s work as ‘well known’ (page

      -

      Simon Brooke: Notes for a thesis entitled Page : 35

      -

      l· 1¤ ·•I f I‘ · - • sustai n !q.u •q·• •\$€

      -

      14), and paraphrasing one of Feyerabend’s central points (although without

      -

      acknowledging it): l

      -

      "… one theory says that there are electrons, and the other says that

      -

      there may not be. Even if the observable phenomena are as Rutherford

      -

      says, the unobservable may be different. However, the positivists

      -

      would say, if you argue that way, you automatically become a prey to

      -

      scepticism. You will have to admit that there are possibilities that you

      -

      cannot prove or disprove by experiment, and so you will have to say we

      -

      cannot know what the world is like. Worse; you will have no reason to

      -

      reject any number of outlandish possibilities; demons, witchcraft,

      -

      hidden powers contirbuting to fantastic ends." (page 35, my emphasis)

      -

      Well yes, precisely. And although it is possible that the positivists would say

      -

      it, Feyerabend did say it, repeatedly; and the choice of words seems to me to

      -

      betray a consciousness of this [see for example Feyerabend, 81, vol 1, foot of

      -

      page 196 - which other evidence (below) shows us van Fraassen was familiar

      -

      with]. But the only time van Fraassen addresses an argument of Feyerabend’s

      -

      directly, he dismisses it as ‘…a totally false issue…’ (page 93). Let us look a

      -

      P little at the context for this. 3

      -

      van Fraassen is discussing the centrality of explanation to science, citing -

      -

      and accepting - Nagel’s strong claim [Nagel 61, page 4], and using incidentally

      -

      the same passage from Nagel as Feyerabend had used in his earlier critique of this

      -

      work [Feyerabend 81, page 52; this paper originally published in BJPS vol 16,

      -

      1964] to illustrate this. He claims that Nagel’s view does not entail realism, but

      -

      will equally support an empiricist view. He now claims that Feyerabend has

      -

      advanced the ‘..totally false..’ argument that, in his paraphrase:

      -

      ’…only Realism is a philosophy that stimulates scientific enquiry;

      -

      anti-realism hampers it." [page 93]

      -

      This is a position that Feyerabend advanced? Really? Feyerabend whose

      -

      central thesis might be summed up in his phrase "The only principle that does

      -

      not inhibit progress is: anything goes." [Feyerabend 75, p10: F’s emphasis]. van

      -

      Fraassen refers us to Feyerabend’s paper [in

      -

      Feyerabend 81 vol 1]. What Feyerabend in fact says (forgive me ifi quote at

      -

      length) is:

      -

      "To sum up: the issue between realism and instrumentalism has g`

      -

      A many facets….. There are arguments for instrumentalism which

      -

      concern specific theories such as the quantum theory or the

      -

      heliocentric hypothesis and which are based on specific facts and well

      -

      confirmed theories. It was shown that to demand realism in these cases

      -

      * amounts to demanding support for implausible conjectures which

      -

      possess no independent empirical support and which are inconsistent

      -

      with facts and well confirmed theories. It was also shown that this is a

      -

      plausible demand which immediately follows from the principle of

      -

      testability. Hence realism is preferable to instrumentalism even in

      -

      these most difficult cases." [Feyerabend 81 vol 1 pp 201-2;

      -

      Feyerabend’s emphasis.

      -

      ‘Realism is preferable to instrumentalism’. That is a very different (and far

      -

      weaker) claim than ‘only Realism stimulates scientific enquiry’. So the

      -

      totally false issue is of van Fraassen’s own devising, and has nothing to do with

      -

      Feyerabend.

      -

      Simon Brooke: Notes for a thesis entitled Page : 36

      -

      ll‘ tan ·• l“`l · anu, ne u lan uw •\$¢

      -

      l have gone on at some length about van Fraassen’s slight (and slighting)

      -

      mention of Feyerabend. Why? Well, because van Fraassen, continueing the now

      -

      moribund debate between realsim and empiricism in order to defend the latter,

      -

      addresses Feyerabend’s criticisms of neither doctrine. This seems an

      -

      extraordinary ommission.

      -

      <Here insert some stuff about van Fs account of exp/anati0n…>

      -

      Toulmin

      -

      Turning aside for the moment from those philosophers who have made a study VcL‘&‘/6

      -

      of explanation per se, there is another whose work is currently attracting

      -

      fashionable attention in Expert Systems (and especially mechanised explanation)

      -

      circles; one must make passing reference to Toulmin, and, unless one chooses to

      -

      use his argument schema, one must produce a very good argument for not doing

      -

      so. Therfore it is important to know what he actually argued.

      -

      A Tou|min’s programme was to replace the syllogistic with a new logical

      -

      schema of his own. He did not address symbolic logic except by dismissing it as

      -

      irrelevant to the study of real world arguments:

      -

      "We shall have to replace mathematically-idealised logical

      -

      relations - timeless context-free relations between either statements

      -

      or propositions — by relations which in practical fact are no more than

      -

      the statements to which they relate. This is not to say that the

      -

      elaborate mathematical systems which constitute ‘symbolic logic’ must

      -

      now be thrown away; but only that people with intellectual capital

      -

      invested in them should retain no illusions about the extent of their

      -

      relevance to practical arguments." (Toulmin 58, p 185)

      +

      Toulmin

      +

      Turning aside for the moment from those philosophers who have made a study of explanation per se, there is another whose work is currently attracting fashionable attention in Expert Systems (and especially mechanised explanation) circles; one must make passing reference to Toulmin, and, unless one chooses to use his argument schema, one must produce a very good argument for not doing so. Therfore it is important to know what he actually argued.

      +

      A Toulmin’s programme was to replace the syllogistic with a new logical schema of his own. He did not address symbolic logic except by dismissing it as irrelevant to the study of real world arguments:

      +
      +

      “We shall have to replace mathematically-idealised logical relations - timeless context-free relations between either statements or propositions — by relations which in practical fact are no more than the statements to which they relate. This is not to say that the elaborate mathematical systems which constitute ‘symbolic logic’ must now be thrown away; but only that people with intellectual capital invested in them should retain no illusions about the extent of their relevance to practical arguments.” (Toulmin 58, p 185)

      +

      or again:

      -

      "…the question needs to be pressed, whether this branch of

      -

      mathematics (propositional calculus) is entitled to the name ’logical

      -

      theory’. If we give it this name, we imply that the propositional

      -

      calculus plays a part in the assessment of actual arguments comparable

      -

      to that played by physical theory in explaining actual physical

      -

      phenomena. But this we have seen reason to doubt: this branch of ~

      -

      " mathematics does not form the theoretical part of logic… By now, the

      -

      mathematicians logic has become a frozen calculus, having no

      -

      functional connection with the canons for assessing the strength and

      -

      _` cogency of arguments." (Ibid, p 186 - and he goes on in this vein!)

      -

      These contentions seem polemical, even propagandistic, in tone; they are

      -

      certainly not, in Tou|min‘s own terminology, ‘candid’. They advance scant

      -

      evidence in support of their allegations. They seem out of place in a work whose

      -

      matter is the analysis of argument; and they lie especially uneasy with TouImin’s

      -

      claim to be seeking to make argument more scrutable.

      -

      He goes on to attack the concept of ‘logicaI form’ and ‘formal validity’ in

      -

      argument:

      -

      Simon Brooke: Notes for a thesis entitled Page : 37

      -

      1: nan ·•. · ·n · an ,…».ent -1 U an u ·•. 1- \$3

      -

      "…the suggestion that validity is to be explained in terms of

      -

      ‘formal properties’, in any geometric sense, loses its plausibility."

      -

      (Ibid, p 120)

      -

      He argues that the conception that arguments in general could or should have a

      -

      logical form arises out of a false start in the study of logic:

      -

      "The development of logical theory… began historically with the

      -

      study of a rather special class of arguments -_ namely, the class of

      -

      unequivocal, analytic, formally valid arguments with a universal

      -

      statement as ‘major premiss’. Arguments in this class are exceptional

      -

      in four different ways, which together make them a bad example for

      -

      general study." (Ibid, p 144)

      -

      Clearly, if arguments have no logical form, it is not possible to advance a

      -

      decision process for them, and Toulmin does not attempt to do so. Rather, the

      -

      burden of his argument is that decision processes are (for real world arguments)

      -

      impossible in principle.

      -

      Thus those practitioners in the field of Expert Systems who advance Toulmin

      -

      ,·— as an authority must face up to this corrolary: if Toulmin’s arguments are valid,

      -

      then there cannot ever be a successful Expert System based on any technology we

      -

      have now available, as all current Expert Systems are based on some logical

      -

      formalism (even if, as in the case of production systems, this formalism is

      -

      crude); and all, certainly, claim to be decision processes for arguments in their

      -

      domain. As such, according to Toulmin, they are the modern equivalents of the

      -

      PhiIosophers’ stone - they cannot exist.

      -

      He was, to be fair to him, writing in the year that LISP was being developed,

      -

      when the posibility of mechanical inference was dreamed of only by visionaries

      -

      like Turing; nevertheless the cavalier manner in which he dismisses all of the

      -

      19th and 20th century advances in logic significantly weakens his claims to be

      -

      taken seriously in this field.

      -

      But if Toulmin cannot be taken seriously as a logician, is there any residual

      -

      value in his work on argument? I think it is possible that there is, because the

      -

      argument schema with which he hoped to replace both the traditional syllogism,

      -

      and the formalisms of modern logic, does indeed capture the content of normal

      -

      conversational discussion in an easily manageable form. Had Toulmin advanced

      -

      this and this only, I think he might have been taken more seriously; and I think x

      -

      A there is merit in the current revival of interest in it.

      -

      the Schema

      -

      Toulmin’s concern is with arguments as they are presented informally, in

      -

      * conversation or writing, and the relation between the form of such informal

      -

      arguments and the forms recognised by formal logic. `

      -

      He questions whether the aristotelian ‘standard form’ of an argument is

      -

      ‘candid’; that is, whether it is presented in such a way as to make its merits as

      -

      argument most manifest. He suggests that the analysis into only three elements,

      -

      major premiss, minor premiss, conclusion may be artificially simplified:

      -

      "Simplicity is of course a merit, but may it not in this case have

      -

      been bought too dearly? Can we properly classify all the elements in

      -

      our arguments under the three headings, ‘major premiss’, ’minor

      -

      premiss’ and ‘conclusion’, or are these categories misleadingly few in

      -

      Simon Brooke: Notes for a thesis entitled Page : 38

      -

      U’ al. “! ‘·1 · any t •n |»•1 •qf•. •¢\$

      -

      number? Is there even enough similarity between major and minor

      -

      premisses for them usefully to be yoked together by the single

      -

      name…?"

      -

      He draws on the practice of jurisprudence to find alternative schemae; and

      -

      synthesises one such comprising the following elements: a statement of some

      -

      assertion, which implicitly carries with it a g_|_a_j_m_ as to the truth of the

      -

      assertion; and data, information which is consensual at the time of argument (or

      -

      is supported by some futher argument), which tends to support that claim; some

      -

      inference rule, a warrant, which will allow the argument to move from the data

      -

      to the claim (for example, ‘all as are bs’), again optionally supported by some

      -

      further argument or bagking; an optional ggjalifigr (e.g. ‘probably’, ‘l believe’);

      -

      and, implicit in the qualifier, the possibility of a rebuttal:

      -

      D —————··-— > S0, O , C

      -

      I I

      -

      I I

      -

      Since Un/ess

      -

      ’ W F?

      -

      I

      -

      on account of

      -

      B

      -

      (after Toulmin, p 104: my emphasis of optional elements)

      -

      In conversation, Toulmin argues, it may be natural simply to say ’<data> so

      -

      <c|aim>‘ ; to say ’<c|aim> because <warrant> because <data>’ "…strikes us as

      -

      cumbrous and artificial, for it_puts in an extra step which is trivial and

      -

      unnecessary".

      -

      Toulmin sets out to validate this schema by comparing it with the syllogism,

      -

      and asking "’What corresponds in the syllogism to our distinction between data,

      -

      warrant, and backing?"’ He devotes special attention to arguments of the forms

      -

      ‘Almost all A’s are B’s’ and ‘Scarcely any A’s _are B’s’ - forms which are, of

      -

      course, of the utmost importance in default logics, but which are beyond the

      -

      scope of the syllogistic. He shows that such arguments are representable using

      -

      his schema without difficulty, and that the traditional syllogism forms are also so

      -

      representable.

      -

      f But beyond this he observes that the major premiss of a syllogism plays a

      -

      dual role with hegemonistic implications: it is at once an inference step and an

      -

      assertion of some piece of information. Thus one may challenge it in its role as

      -

      _; warrant, on the basis that it is not relevant to the case, and as backing, on the

      -

      grounds that it is not true. TouImin’s schema, by separating these roles, makes ` . _ E

      -

      clearer from what grounds a counter argument can be launched. °_ i._ ` `

      -

      While TouImin’s ambitious claims for his schema as the authoritative tt-, . _ f,

      -

      representation of argument - and his audacious dismissal of modern logic - seem Q_ A »_ ·_ ·

      -

      unworthy of attention, his representation shema does offer some merits in the W ; ‘ \ M I

      -

      representation of real world arguments, especially those which appeal to default .»—l— .,,_

      -

      reasoning. Furthermore, the fact that these argument structures can be ’daisy-

      -

      . chained’ offers a convenient way to pack up large arguments into a structure

      -

      which can be unfolded to any given level of detail, and this property makes the

      -

      Simon urookez Notes ror a tnesns emmeo r-age ; eu

      -

      · {n w 1.··1· qa .• ·n. •n |·.•n nv . •\$\$

      -

      schema an interesting candidate argument representation as we look for ways to

      -

      control the amount of detail revealed to the user of an Expert System.

      -

      His contention that argument can be hegemonic is one which I shall want to

      -

      examine further.

      -

      Towards a Situation Semantic account of Explanation

      -

      Part of Barwise and Perry’s programme in constructing Situation Semantics

      -

      was to elucidate the problem of the transfer of knowledge from one person to

      -

      another, and this is, of course, one of the central problems in an account of

      -

      explanation.

      -

      However, they give no account of explanation as such. What follows is my

      -

      guess at what their account would look like, had they formally stated it. This

      -

      should not be taken too seriously, as their formalism is rich and complex, and I

      -

      have by no means mastered it. Certainly, any howlers in what follows all my own

      -

      work. `

      -

      My first ‘cut’ at the problem looked like this. An explanation was to be that

      -

      which happened in a situation E defined:

      -

      ° E := at jj: understands, _a, gg no

      -

      understands, p_, _c_; yes

      -

      enquirlng, g; yes

      -

      addressing, _a_, _b_; yes

      -

      S¤Yl¤9. Q. 9; l/GS

      -

      subject, g, g; yes

      -

      atlz: responding, bi, g; yes

      -

      addressing, _b_, a_; yes

      -

      \$¤Yl¤9. 9.. ll; VSS

      -

      subject, _u, jg; yes

      -

      atj3: understands, gd, g; yes

      -

      understands, p_, _c_; yes `

      -

      I1 `< lz ’<Is

      -

      »» where: a, b are some actors; c is some concept; q, u are some utterances. "

      -

      This begs a number of questions. Firstly, what relationship is meant by

      -

      ’understands, x, y’ ? This question is, of course, the central one for the whole

      -

      programme of Situation Semantics; when it can be answered, the programme

      -

      *1 will have succeeded. Secondly, how can we represent the (presumed) causal

      -

      dependence of the understanding at I3 on the responding at I2 ? Thirdly, what

      -

      implications (if any) does this have for the semantic content of u?

      -

      However, this definition does have some points of value. Firstly, an

      -

      explanation is located in a situation with at least two roles (which,

      -

      incidentally, cannot be taken by the same individual); secondly, a transfer of

      -

      understanding takes place. Neither of these points are met by traditional

      -

      accounts.

      -

      So what we need to add is something like this. The sage’s response, u, must

      -

      be seen as a list of statements [sq, sg, sn], Such that, for any statement sj

      -

      Simon Brooke: Notes for a thesis entitled Page : 40

      -

      ll: ·.¤ ‘• .|.<·n · aan .•tn» •n |q•1 •··• •\$\$

      -

      in u, sj is understandable in terms of [<students state of knowledge at l1> + sj

      -
        -
      • -
          -
        • Sl-1]. and also that c, the concept originally asked about, is
          • -
        • -
      -

      understandable in-terms of [<students state of knowledge at l1> + sj + +

      -

      sn]. This (fortunately) accords with Barwise and Perry’s understanding:

      -

      "An utterance u of a sentence l/I gives us not just one discourse _

      -

      situation d for 1/J that is part of u, but also discourse situations d G for

      -

      every constituent expression 0 of ltr, discourse situations that are also

      -

      parts of u… Thus, part of what the utterance gives us is the set

      -

      {d G : cz is zlr or a constituent of lp}

      -

      of discourse situations." [Ibid p 123]

      -

      This is inadequate, because (among other things) it fails to represent the

      -

      negotiation which is inherent in the construction of many real world

      -

      explanations.

      -

      However, it appears to be a step along a potentially interesting path, and

      -

      one which I intend to pursue.

      -

      A lemma eeneerning the natjjre ef pereeptign

      -

      The major argument which l wish to develop in this chapter is based on a very

      -

      important - and contentious - assumption: there may (or may not) be such a thing

      -

      as a real world, but it’s existance is largely irrelevant, as if it does exist, we are

      -

      unable to percieve it directly. So before going on to advance this major argument, l

      -

      will attempt to support this lemma.

      -

      In van Fraassen’s words, "the human organism is, from the point of view of

      -

      physics, a certain kind of measuring apparatus. As such, it has certain inherent

      -

      |imitations… " [van Fraassen 80, p 17] Precisely: and as van Fraassen observes,

      -

      our perceptions of the world are conditioned by the nature of this apparatus, and by

      -

      these limitations, which, as he goes on to claim, "…wilI be described in the final

      -

      physics and biology." [ibid] But how can this be? We are to investigate the nature of

      -

      these instruments, using, as analytic tools, the instruments themselves.

      -

      Take for example the human eye. We know what the eye looks like; we’ve seen

      -

      many of them: with our eyes. We know their physical nature, because biologists have

      -

      dissected them, and using their eyes, have made careful diagrammes of what they 7;

      -

      A have seen, which we, in turn, can examine using our eyes. F `

      -

      So, if our theories about the nature of the eye are right, and it does indeed

      -

      project a two dimensional image of a three dimensional world (supposing such

      -

      at exists) onto our retinas, then our theories about the nature of the eye are right.

      -

      This argument is not as far fetched as it sounds: after all, the memory of a

      -

      computer [assuming, for the moment, that such things exist] is strictly one

      -

      dimensional - a vector of cells. Yet Computer-aided design software, for example, or

      -

      flight simulator software, renders an image from this one-dimensional environment

      -

      onto a two dimensional screen in such a way that we interpret it in three dimensions.

      -

      Simon Brooke: Notes for a thesis entitled Page : 41

      -

      Meclgegieeg lgteregce egg Explegeticg Qragghtegtegj ·, 21[§[§§

      -

      If such transformations between a one dimensional reality and a three dimensional

      -

      appearance are possible in a machine, why not in our own optical systems?1

      -

      Furthermore, our theories about the nature of world are conditioned by the

      -

      languages in which we express them. Different languages allow for the descrition of

      -

      different theories about reality. Again, different communities (or even individuals)

      -

      using what they believe to be the same language (say, for example, English) may

      -

      attatch sufficiently different interpretations to the same linguistic symbols and

      -

      constructs that communication fails, without either of the parties being aware that

      -

      it has failed. This point, about the incommensurability of (some) theories has been

      -

      made many times [see eg Kuhn, Feyerabend]; but some of the consequences require

      -

      exploration.

      -

      An erggment cencerning the netgre cf explgneticn

      -

      Firstly, if we cannot access reality except through the medium of theory, then

      -

      Nagel’s claim that an explanation is a mapping from a statement to reality must fall.

      -

      It becomes clear that explanation can at best be a mapping from a statement to a

      -

      theory. ls this a good account of the nature of explanation? .

      -

      A Well, let us consider what, in common sense, we think of as ‘a good explanation’.

      -

      We feel we have recieved a good explanation if we ‘understand’ both the explanation

      -

      and the explicandum; if it ‘makes sense’: if, in fact, we do not percieve it as grossly

      -

      inconsistent with the body of ‘be|ief’ or ’know|edge’ which we already hold.

      +
      +

      “…the question needs to be pressed, whether this branch of mathematics (propositional calculus) is entitled to the name ‘logical theory’. If we give it this name, we imply that the propositional calculus plays a part in the assessment of actual arguments comparable to that played by physical theory in explaining actual physical phenomena. But this we have seen reason to doubt: this branch of mathematics does not form the theoretical part of logic… By now, the mathematicians logic has become a frozen calculus, having no functional connection with the canons for assessing the strength and cogency of arguments.” (Ibid, p 186 - and he goes on in this vein!)

      +
      +

      TODO: I can use precisely this - and van Frassen’s work, too - to illustrate and underline my case later that the purpose of argument is hegemonistic, not truth-seeking. This is so clearly polemical.

      +

      These contentions seem polemical, even propagandistic, in tone; they are certainly not, in Tou|min‘s own terminology, ‘candid’. They advance scant evidence in support of their allegations. They seem out of place in a work whose matter is the analysis of argument; and they lie especially uneasy with Touimin’s claim to be seeking to make argument more scrutable.

      +

      He goes on to attack the concept of ‘logicaI form’ and ‘formal validity’ in argument:

      +
      +

      “…the suggestion that validity is to be explained in terms of ‘formal properties’, in any geometric sense, loses its plausibility.” (Ibid, p 120)

      +
      +

      He argues that the conception that arguments in general could or should have a logical form arises out of a false start in the study of logic:

      +
      +

      “The development of logical theory… began historically with the study of a rather special class of arguments -_ namely, the class of unequivocal, analytic, formally valid arguments with a universal statement as ‘major premiss’. Arguments in this class are exceptional in four different ways, which together make them a bad example for general study.” (Ibid, p 144)

      +
      +

      Clearly, if arguments have no logical form, it is not possible to advance a decision process for them, and Toulmin does not attempt to do so. Rather, the burden of his argument is that decision processes are (for real world arguments) impossible in principle.

      +

      Thus those practitioners in the field of Expert Systems who advance Toulmin as an authority must face up to this corrolary: if Toulmin’s arguments are valid, then there cannot ever be a successful Expert System based on any technology we have now available, as all current Expert Systems are based on some logical formalism (even if, as in the case of production systems, this formalism is crude); and all, certainly, claim to be decision processes for arguments in their domain. As such, according to Toulmin, they are the modern equivalents of the PhiIosophers’ stone - they cannot exist.

      +

      He was, to be fair to him, writing in the year that LISP was being developed, when the posibility of mechanical inference was dreamed of only by visionaries like Turing; nevertheless the cavalier manner in which he dismisses all of the 19th and 20th century advances in logic significantly weakens his claims to be taken seriously in this field.

      +

      But if Toulmin cannot be taken seriously as a logician, is there any residual value in his work on argument? I think it is possible that there is, because the argument schema with which he hoped to replace both the traditional syllogism, and the formalisms of modern logic, does indeed capture the content of normal conversational discussion in an easily manageable form. Had Toulmin advanced this and this only, I think he might have been taken more seriously; and I think there is merit in the current revival of interest in it.

      +

      The Schema

      +

      Toulmin’s concern is with arguments as they are presented informally, in conversation or writing, and the relation between the form of such informal arguments and the forms recognised by formal logic.

      +

      He questions whether the aristotelian ‘standard form’ of an argument is ‘candid’; that is, whether it is presented in such a way as to make its merits as argument most manifest. He suggests that the analysis into only three elements, major premiss, minor premiss, conclusion may be artificially simplified:

      +
      +

      “Simplicity is of course a merit, but may it not in this case have been bought too dearly? Can we properly classify all the elements in our arguments under the three headings, ‘major premiss’, ‘minor premiss’ and ‘conclusion’, or are these categories misleadingly few in number? Is there even enough similarity between major and minor premisses for them usefully to be yoked together by the single name…?”

      +
      +

      He draws on the practice of jurisprudence to find alternative schemae; and synthesises one such comprising the following elements: a statement of some assertion, which implicitly carries with it a claim as to the truth of the assertion; and data, information which is consensual at the time of argument (or is supported by some futher argument), which tends to support that claim; some inference rule, a warrant, which will allow the argument to move from the data to the claim (for example, ‘all as are bs’), again optionally supported by some further argument or bagking; an optional qualifier (e.g. ‘probably’, ‘I believe’); and, implicit in the qualifier, the possibility of a rebuttal:

      +

      Argument schama after Toulmin, p 104

      +

      In conversation, Toulmin argues, it may be natural simply to say ‘<data> so <c|aim>’ ; to say ‘<c|aim> because <warrant> because <data>’ “…strikes us as cumbrous and artificial, for it puts in an extra step which is trivial and unnecessary”.

      +

      Toulmin sets out to validate this schema by comparing it with the syllogism, and asking "‘What corresponds in the syllogism to our distinction between data, warrant, and backing?"’ He devotes special attention to arguments of the forms ‘Almost all A’s are B’s’ and ‘Scarcely any A’s _are B’s’ - forms which are, of course, of the utmost importance in default logics, but which are beyond the scope of the syllogistic. He shows that such arguments are representable using his schema without difficulty, and that the traditional syllogism forms are also so representable.

      +

      But beyond this he observes that the major premiss of a syllogism plays a dual role with hegemonistic implications: it is at once an inference step and an assertion of some piece of information. Thus one may challenge it in its role as warrant, on the basis that it is not relevant to the case, and as backing, on the grounds that it is not true. TouImin’s schema, by separating these roles, makes clearer from what grounds a counter argument can be launched.

      +

      {**TODO**: Again back-reference this when I’m arguing that argument is hegemonistic!}

      +

      While TouImin’s ambitious claims for his schema as the authoritative representation of argument - and his audacious dismissal of modern logic - seem unworthy of attention, his representation schema does offer some merits in the representation of real world arguments, especially those which appeal to default reasoning. Furthermore, the fact that these argument structures can be ‘daisy-chained’ offers a convenient way to pack up large arguments into a structure which can be unfolded to any given level of detail, and this property makes the schema an interesting candidate argument representation as we look for ways to control the amount of detail revealed to the user of an Expert System.

      +

      His contention that argument can be hegemonic is one which I shall want to examine further.

      +

      Towards a Situation Semantic account of Explanation

      +

      Part of Barwise and Perry’s programme in constructing Situation Semantics was to elucidate the problem of the transfer of knowledge from one person to another, and this is, of course, one of the central problems in an account of explanation.

      +

      However, they give no account of explanation as such. What follows is my guess at what their account would look like, had they formally stated it. This should not be taken too seriously, as their formalism is rich and complex, and I have by no means mastered it. Certainly, any howlers in what follows all my own work.

      +

      My first ‘cut’ at the problem looked like this. An explanation was to be that which happened in a situation E defined:

      +
      E := at I1: understands, a, c; no
+    understands, b, c; yes
+    enquirlng, a; yes
+    addressing, a, b; yes
+    saying, a, q; yes
+    subject, q, c; yes
+
+  at I2: responding, b, q; yes
+    addressing, b, a; yes
+    saying, b, u; yes
+    subject, u, c; yes
+
+  at I3: understands, a, c; yes
+    understands, b, c; yes
+
+  I1 < I2 < I3
+
      +

      where: a, b are some actors; c is some concept; q, u are some utterances.

      +

      This begs a number of questions. Firstly, what relationship is meant by ’understands, x, y’ ? This question is, of course, the central one for the whole programme of Situation Semantics; when it can be answered, the programme will have succeeded. Secondly, how can we represent the (presumed) causal dependence of the understanding at I3 on the responding at I2 ? Thirdly, what implications (if any) does this have for the semantic content of u?

      +

      However, this definition does have some points of value. Firstly, an explanation is located in a situation with at least two roles (which, incidentally, cannot be taken by the same individual); secondly, a transfer of understanding takes place. Neither of these points are met by traditional accounts.

      +

      So what we need to add is something like this. The sage’s response, u, must be seen as a list of statements [s1, s2, … sn], Such that, for any statement sj in u, sj is understandable in terms of [<student’s state of knowledge at I1> + s1 + Sj-1]. and also that c, the concept originally asked about, is understandable in terms of [<student’s state of knowledge at I1> + sj + … + sn]. This (fortunately) accords with Barwise and Perry’s understanding:

      +
      +

      "An utterance u of a sentence φ gives us not just one discourse situation d for φ that is part of u, but also discourse situations dα for every constituent expression α of φ, discourse situations that are also parts of u… Thus, part of what the utterance gives us is the set

      +

      {dα : α is φ or a constituent of φ}

      +

      of discourse situations." [Ibid p 123]

      +
      +

      This is inadequate, because (among other things) it fails to represent the negotiation which is inherent in the construction of many real world explanations.

      +

      However, it appears to be a step along a potentially interesting path, and one which I intend to pursue.

      +

      A lemma concerning the nature of perception

      +

      The major argument which I wish to develop in this chapter is based on a very important - and contentious - assumption: there may (or may not) be such a thing as a real world, but it’s existance is largely irrelevant, as if it does exist, we are unable to percieve it directly. So before going on to advance this major argument, I will attempt to support this lemma.

      +

      In van Fraassen’s words, “the human organism is, from the point of view of physics, a certain kind of measuring apparatus. As such, it has certain inherent limitations… ” [van Fraassen 80, p 17] Precisely: and as van Fraassen observes, our perceptions of the world are conditioned by the nature of this apparatus, and by these limitations, which, as he goes on to claim, “…wilI be described in the final physics and biology.” [ibid] But how can this be? We are to investigate the nature of these instruments, using, as analytic tools, the instruments themselves.

      +

      Take for example the human eye. We know what the eye looks like; we’ve seen many of them: with our eyes. We know their physical nature, because biologists have dissected them, and using their eyes, have made careful diagrams of what they have seen, which we, in turn, can examine using our eyes.

      +

      So, if our theories about the nature of the eye are right, and it does indeed project a two dimensional image of a three dimensional world (supposing such at exists) onto our retinas, then our theories about the nature of the eye are right.

      +

      This argument is not as far fetched as it sounds: after all, the memory of a computer [assuming, for the moment, that such things exist] is strictly one dimensional - a vector of cells. Yet Computer-aided design software, for example, or flight simulator software, renders an image from this one-dimensional environment onto a two dimensional screen in such a way that we interpret it in three dimensions.

      +

      If such transformations between a one dimensional reality and a three dimensional appearance are possible in a machine, why not in our own optical systems? [1]

      +

      Furthermore, our theories about the nature of world are conditioned by the languages in which we express them. Different languages allow for the description of different theories about reality. Again, different communities (or even individuals) using what they believe to be the same language (say, for example, English) may attatch sufficiently different interpretations to the same linguistic symbols and constructs that communication fails, without either of the parties being aware that it has failed. This point, about the incommensurability of (some) theories has been made many times [see eg Kuhn, Feyerabend]; but some of the consequences require exploration.

      +

      An argument concerning the nature of explanation

      +

      Firstly, if we cannot access reality except through the medium of theory, then Nagel’s claim that an explanation is a mapping from a statement to reality must fall.

      +

      It becomes clear that explanation can at best be a mapping from a statement to a theory. ls this a good account of the nature of explanation? . Well, let us consider what, in common sense, we think of as ‘a good explanation’. We feel we have recieved a good explanation if we ‘understand’ both the explanation and the explicandum; if it ‘makes sense’: if, in fact, we do not percieve it as grossly inconsistent with the body of ‘belief’ or ’knowledge’ which we already hold.

      For example, most modern Western people would not think that the statement:

      -

      ‘the God Fla drives his chariot daily across the rainbow bridge’

      -

      was a good explanation of why the sun rises and sets; we do not believe that there

      -

      is a God Fla, nor that what we percieve as the sun is identical with this being, nor

      -

      that a rainbow is sufficiently rigid and strong to bear the weight of such a being,

      -

      lThis argument that our perception of a ‘real world’ does not prove its existence is not

      -

      new, of course. Here is a classic statement of a similar argument from BerkeIey’s Fire;

      -

      Dielegge cf Hylee end Philcnegcz

      -

      Hyl.: Do we not perceive the stars and moon, for example, to be a

      -

      A great way off? Is not this, I say, manifest to the senses? I

      -

      Phil.: Do you not in a dream too perceive those or like objects?

      -

      Hyl.: I do.

      -

      )‘ Phil.: And have they not then the same appearance of distance?

      -

      Hyl.: They have.

      -

      Phil.: But you do not htence conclude the apparitions in a dream to q..;F

      -

      be without the mind?

      -

      Hyl.: By no means.

      -

      Phil.: You ought not therefore to conclude that sensible objects are

      -

      without the mind, from their appearance or manner wherein they are

      -

      percieved.

      -

      Hyl.: I acknowledge it.

      -

      Simon Brooke: Notes for a thesis entitled Page : 42

      -

      should it exist. But to a first kingdom Egyptian, it may have been an excellent

      -

      explanation. Similarly, that first kingdom Egyptian would not accept the statement:

      -

      ‘the Earth rotates on its axis once every day’

      -

      as a good explanation for the occurance of the same phenomenon. He would know

      -

      perfectly well that the earth, being fixed, could not rotate on its axis. And even if it

      -

      could, why should this influence the daily ritual of Ra?

      -

      We consider an explanation good if it maps a statement about theexplicandum

      -

      onto the theory, or body of belief, which we currently ho|d.1

      -

      [Main text of argument. In the tradition of ‘philosophy of science’ I intend to

      -

      draw on examples from two genuine debates, drawn in this instance from the

      -

      development of the theory of evolution. These debates are

      -

      The debate between Huxley and Kropotkin over whether co-operation or

      -

      competition was the more important factor in the survival of species.

      -

      Kropotkin, a leading Anarchist, sought to show that human beings (among

      -

      other animals) were inherently co-operative, and (implied conclusion)

      -

      »· would get along fine in the absence of government. Huxley, a Tory, sought to

      -

      show that, on the contrary, competition (and, implicitly, capitalism) red in

      -

      tooth and claw was ‘natural’.

      -

      The debate between Bateson and Kammerer over whether aquired

      -

      characteristics were inherited.

      -

      Kammerer, then the only scientist capable of breeding many species of

      -

      amphibian in captivity, showed in a series of experiments that

      -

      characteristics aquired by parents were inherited by their offspring.

      -

      Bateson, in a series of increasingly virulent attacks, ultimately claimed that

      -

      these experiments were fraudulent. As no-one else was even capable of

      -

      breeding the creatures involved, they could not be repeated.

      -

      Kammerer was a communist, and the implicit argument behind his work

      -

      was that human beings were perfectable; that some parts of the benefits of

      -

      humane education and culture would be transmitted. Bateson was again a Tory,

      -

      though not as politically committed as the other figures discussed.

      -

      In these debates it is clear that the protagonists sought ot explain a

      -

      phenomenon - in this case evolution - in terms of theories which supported their _

      -

      » own views of the world. The act of explanation was clearly being used as a polemic

      -

      act, to try to pursuade the explainee of the correctness of the explainers

      -

      ideological stance]

      -

      4.

      -

      ll am grateful to Vernon Pratt for helping me clarify the consequences that this doctrine

      -

      has for the concepts of ‘theory’ and ‘belief’. lf it is the case that there is no access to a

      -

      ‘real world’, then all statements about the nature of the world are of equal -

      -

      undifferentiable - validity (except in so far as some aesthetic criteria may be applied to

      -

      them). lt remains possible to differentiate between a belief - an unsupported statement

      -

      about the nature of the world - and a theory: a statement that the world has some

      -

      property as a consequence of certain other properties which it may have. However, it

      -

      seems to me that this distinction is of little practical importance.

      -

      Simon Brooke: Notes for a thesis entitled Page : 43

      -

      li‘ al ,‘! n··n ¢ in L.•-,ni •a |a•1•¤·• •\$¢

      -

      Linguistics

      -

      Psychology

      -

      Referenses:

      -

      PhHosophy · V

      -

      Barwise, Situations and Attitudes (?)

      -

      Feyerapend, Ageinst Metheg

      -

      ven Fresssen, B Q: The Seientifis Image: Qlerengen Press, Qxfgrg, 1QSQ

      +
      'the God Ra drives his chariot daily across the rainbow bridge'
+
      +

      was a good explanation of why the sun rises and sets; we do not believe that there is a God Ra, nor that what we percieve as the sun is identical with this being, nor that a rainbow is sufficiently rigid and strong to bear the weight of such a being should it exist. But to a first kingdom Egyptian, it may have been an excellent explanation. Similarly, that first kingdom Egyptian would not accept the statement:

      +
      'the Earth rotates on its axis once every day'
+
      +

      as a good explanation for the occurance of the same phenomenon. He would know perfectly well that the earth, being fixed, could not rotate on its axis. And even if it could, why should this influence the daily ritual of Ra?

      +

      We consider an explanation good if it maps a statement about the explicandum onto the theory, or body of belief, which we currently hold.

      +

      [Main text of argument. In the tradition of ‘philosophy of science’ I intend to draw on examples from two genuine debates, drawn in this instance from the development of the theory of evolution. These debates are

      +

      The debate between Huxley and Kropotkin over whether co-operation or competition was the more important factor in the survival of species.

      +

      Kropotkin, a leading Anarchist, sought to show that human beings (among other animals) were inherently co-operative, and (implied conclusion) would get along fine in the absence of government. Huxley, a Tory, sought to show that, on the contrary, competition (and, implicitly, capitalism) red in tooth and claw was ‘natural’.

      +

      The debate between Bateson and Kammerer over whether acquired characteristics were inherited.

      +

      Kammerer, then the only scientist capable of breeding many species of amphibian in captivity, showed in a series of experiments that characteristics aquired by parents were inherited by their offspring. Bateson, in a series of increasingly virulent attacks, ultimately claimed that these experiments were fraudulent. As no-one else was even capable of breeding the creatures involved, they could not be repeated.

      +

      Kammerer was a communist, and the implicit argument behind his work was that human beings were perfectable; that some parts of the benefits of humane education and culture would be transmitted. Bateson was again a Tory, though not as politically committed as the other figures discussed.

      +

      In these debates it is clear that the protagonists sought ot explain a phenomenon - in this case evolution - in terms of theories which supported their own views of the world. The act of explanation was clearly being used as a polemic act, to try to pursuade the explainee of the correctness of the explainers ideological stance]

      +

      Acknowledgments

      +

      I am grateful to Vernon Pratt for helping me clarify the consequences that this doctrine has for the concepts of ‘theory’ and ‘belief’. lf it is the case that there is no access to a ‘real world’, then all statements about the nature of the world are of equal - undifferentiable - validity (except in so far as some aesthetic criteria may be applied to them). It remains possible to differentiate between a belief - an unsupported statement about the nature of the world - and a theory: a statement that the world has some property as a consequence of certain other properties which it may have. However, it seems to me that this distinction is of little practical importance.

      +

      [**TODO**: Talk about what constitutes a good explanation. Draw on work from

      +
        +
      • Linguistics
        • +
      • Psychology]
        • +
      +

      Referenses:

      +

      Philosophy

      +

      Barwise & Perry, Situations and Attitudes {have this}

      +

      Feyerapend, Against Method {have this}

      +

      ven Fresssen, B Q: The Scientific Image: Clarenden Press, Oxford, 1980

      Garfinkel, Forms of Explanation

      Nagel, The Structure of Science

      -

      Pepper, K Qeniesjures and Refujetiens

      -

      A Toulmin, The uses of Argument A

      -

      Linguistics

      -

      Sperber, Relevance

      -

      Psychology

      -

      Antaki, Lay Explanations of Behaviour

      +

      Pepper, K Conjectures and Refutations {don’t have this but might be worth buying}

      +

      A Toulmin, The uses of Argument

      +

      Linguistics

      +

      Sperber, Relevance {have this}

      +

      Psychology

      +

      Antaki, C: Lay Explanations of Behaviour

      +

      Antaki, C: Analysing Everyday Explanation

      Craik, The Nature of Explanation

      -

      Draper, S W·, A User Qentreg Qeneep] ef Explenatien: Alvey Exp SIS 2

      -

      O’Me||ey, Q: Applying Studies ef Neturel Dielegge te Human Qempggter Intereejienz Alvey

      -

      Exp SIQ 2 _

      -

      Artificial Intelligence . ~

      +

      Draper, S W: A User Centred Concept of Explanation: Alvey Exp SIG 2

      +

      O’Melley, Q: Applying Studies of Natural Dialogue to Human Computer Interaction: Alvey Exp SIG 2

      +

      Artificial Intelligence

      A Goguen, Reasoning and Natural Explanation `

      -

      ·k.

      -

      [^1]: Later (p 19), Achinstein refers to ‘the audience’. By contrast, he cites (p 20) an alternative formulation by RJ Mattews in which the audience is explicitly represented.

      \ No newline at end of file +
      +

      [^1]: Later (p 19), Achinstein refers to ‘the audience’. By contrast, hecites (p 20) an alternative formulation by RJ Mattews in which the audience is explicitly represented. [1][OnHylasAndPhilonus.html] Statement of this argument from Berkley’s ‘Three Dialogues of Hylas and Philonous’

    \ No newline at end of file diff --git a/docs/codox/Arboretum.html b/docs/codox/Arboretum.html new file mode 100644 index 0000000..4a8536d --- /dev/null +++ b/docs/codox/Arboretum.html @@ -0,0 +1,6 @@ + +Arboretum

    Project

    Topics

    Namespaces

    Arboretum

    +

    TODO: To be scanned from chapter iv of the 21st June 1988 draft.

    +

    Arboretum screen view showing sample explanations

    +

    Arboretum screen showing a number of generated explanations. This picture was scanned from a 32 year old acetate slide, apologies for quality

    \ No newline at end of file diff --git a/docs/codox/Conception.html b/docs/codox/Conception.html new file mode 100644 index 0000000..06934ca --- /dev/null +++ b/docs/codox/Conception.html @@ -0,0 +1,4 @@ + +Conception

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    Conception

    +

    TODO: To be scanned from chapter v of the 21st June 1988 draft.

    \ No newline at end of file diff --git a/docs/codox/Errata.html b/docs/codox/Errata.html index 1a48473..5968a57 100644 --- a/docs/codox/Errata.html +++ b/docs/codox/Errata.html @@ -1,6 +1,6 @@ -Errata

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    Errata

      -
    1. On title page: the claim that Zaphod Beeblebrox said ‘Hey, what IS truth, man?’ in the printed text of Douglas Adams ‘Hitchhikers Guide to the Galaxy’ is false.
      2. +
    2. On title page: the claim that Zaphod Beeblebrox is quoted as saying ‘Hey, what IS truth, man?’ in the printed text of Douglas Adams ‘Hitchhikers Guide to the Galaxy’ is false.
    \ No newline at end of file diff --git a/docs/codox/History.html b/docs/codox/History.html index efedad6..f4493ca 100644 --- a/docs/codox/History.html +++ b/docs/codox/History.html @@ -1,6 +1,6 @@ -History

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    +History

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    History

    History: Introduction

    The object of this chapter is to describe and discuss the development of Expert System explanations from the beginning’ to the most recent systems. The argument which I will try to advance is that development has been continuously driven by the perceived inadequacy of the explanations given; and that, while many ad hoc, and some principled, approaches have been tried, no really adequate explanation system has emerged. Further, I will claim that, as some of the later and more principled explanation systems accurately model the accounts of explanation advanced in current philosophy, the philosophical understanding of explanation is itself inadequate.

    Family Tree of Systems discussed

    @@ -362,13 +362,17 @@ we shall set up testers for 2273 of card1 in quarter 3

    The application here is to the adjudication of claims to health insurance benefits. The system would be used by the adjudication officer, and the explanation would be sent to the claimant.

    Dear [Name of  Claimant]
 
-You are capable of work and  there are no special circumstances permitting you to be deemed  incapable of work. Although you provided a valid certificate of  explanation, this is insufficient unless either there is evidence  of contact with the disease or you are a known carrier  thereof.
+Although physically capable of work you may
+nonetheless be deemed incapable of work today. You are
+deemed incapable of work for precautionary reasons. You
+are deemed incapable of work on precautionary grounds
+as you are under medical care, and your doctor has
+recommended that you abstain from working.
 
 Yours Sincerely
 
 [your name]
    -

    TODO: this is not a very good Arboretum explanation; I know we did better ones on Widows’ benefit. Check whether I can find a surviving good one, and substitute it.

    Discussion

    It will be seen that this is a short, clear, declarative statement in seemingly natural English, which covers all (and only) the relevant points of a complex case. To be fair, the system does not always do this well, but most of its explanations are of this quality.

    Attempts at more principled approaches

    @@ -408,7 +412,11 @@ Yours Sincerely 
    (EXPLAIN (SHOW  <assertion>))

    Example explanation:

    -
    Well, Peter makes less than 750  dollars, and Peter is under 19, and Harry supports Peter so Peter  is a dependent of Harry's. Uh Peter makes less than 750 dollars  because Peter does not work, and Peter is a dependent of Harry's  because Harry provides more than one half of Peter's  support.
+
    Well, Peter makes less than 750  dollars, and Peter is under 19, and
+Harry supports Peter so Peter  is a dependent of Harry's. Uh Peter
+makes less than 750 dollars  because Peter does not work, and Peter
+is a dependent of Harry's  because Harry provides more than one half
+of Peter's  support.
 
    
 
    I should explain that the application is to the US Federal Income Tax system. This explanation does indeed capture something of the flavour of a natural spoken explanation. Furthermore, it is clearly declarative rather than procedural. However, personally, I find its style rather too informal for textual presentation. I particularly dislike the meaningless ‘Uh’ which is use to tag the supporting point.
    
 
    Discussion
    
diff --git a/docs/codox/Manifesto.html b/docs/codox/Manifesto.html
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+++ b/docs/codox/Manifesto.html
@@ -1,6 +1,6 @@
 
-
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+
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    Machine inference – automated reasoning, the core of what gets called Artificial Intellegence – has ab initio been based on the assumption that the purpose of reasoning was to preserve truth. It is because this assumption is false that the project has thus far failed to bear fruit, that Allan Turing’s eponymous test has yet to be passed.
    
 
    Of course it is possible to build machines which, within the constraints of finite store, can accurately compute theora of first order predicate calculus ad nauseam but such machines do not display behaviour which is convincingly intelligent. They are cold and mechanical; we do not recognise ourselves in them. Like the Girl in the Fireplace’s beautiful clocks, they are precisely inhuman.
    
 
    As Turing’s test itself shows, intelligence is a hegemonic term, a term laden with implicit propaganda. A machine is ‘intelligent’ if it can persuade a person that it is a person. By ‘intelligent’ we don’t mean ‘capable of perfect reasoning’. We mean ‘like us’; and in meaning ‘like us’ we are smuggling under the covers, as semantic baggage, the claim that we ourselves are intelligent.
    
diff --git a/docs/codox/OnHylasAndPhilonus.html b/docs/codox/OnHylasAndPhilonus.html
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@@ -0,0 +1,15 @@
+
+On the First Dialogue of Hylas and Philonous
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    On the First Dialogue of Hylas and Philonous
    
+
    The argument that our perception of a ‘real world’ does not prove its existence is not new, of course. Here is a classic statement of a similar argument from BerkeIey’s First Dialogue of Hylas and Philonous:
    
+
    
+  
    Hyl.: Do we not perceive the stars and moon, for example, to be a A great way off? Is not this, I say, manifest to the senses? I
    
+  
    Phil.: Do you not in a dream too perceive those or like objects?
    
+  
    Hyl.: I do.
    
+  
    Phil.: And have they not then the same appearance of distance?
    
+  
    Hyl.: They have.
    
+  
    Phil.: But you do not thence conclude the apparitions in a dream to be without the mind?
    
+  
    Hyl.: By no means.
    
+  
    Phil.: You ought not therefore to conclude that sensible objects are without the mind, from their appearance or manner wherein they are percieved.
    
+  
    Hyl.: I acknowledge it.
    
+
    
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diff --git a/docs/codox/PredicateSubtext.html b/docs/codox/PredicateSubtext.html
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@@ -1,6 +1,6 @@
 
-
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    On the subtext of a predicate
    
+
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    On the subtext of a predicate
    
 
    Predicates are not atomic. They do not come single spies, but freighted with battalions of inferable subtexts. Suppose Anthony says
    
 
    Brutus killed Caesar in Rome during the ides of March
    
 
    I learn more than just that ‘Brutus killed Caesar in Rome during the ides of March’. I also learn that
    
diff --git a/docs/codox/TheProblem.html b/docs/codox/TheProblem.html
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+++ b/docs/codox/TheProblem.html
@@ -1,6 +1,6 @@
 
-The  Problem
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    The Problem
    
+The  Problem
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    The Problem
    
 
    In this chapter talk about the perceived need for expert system explanations. Advance:
    
 
    the arguments used by expert systems designers, saying why explanations are needed;
    
 
    the arguments used by critics which claim that the explanations given are not good enough.
    
diff --git a/docs/codox/index.html b/docs/codox/index.html
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+++ b/docs/codox/index.html
@@ -1,3 +1,3 @@
 
-Wildwood 0.1.0-SNAPSHOT
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    Wildwood 0.1.0-SNAPSHOT
    Released under the EPL-2.0 OR GPL-2.0-or-later WITH Classpath-exception-2.0
    A general inference library using a game theoretic inference mechanism.
    Installation
    To install, add the following dependency to your project or build file:
    [wildwood "0.1.0-SNAPSHOT"]
    Topics
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    wildwood.core
    TODO: write docs
    Public variables and functions:
    
\ No newline at end of file
+Wildwood 0.1.0-SNAPSHOT
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    Wildwood 0.1.0-SNAPSHOT
    Released under the EPL-2.0 OR GPL-2.0-or-later WITH Classpath-exception-2.0
    A general inference library using a game theoretic inference mechanism.
    Installation
    To install, add the following dependency to your project or build file:
    [wildwood "0.1.0-SNAPSHOT"]
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    wildwood.core
    TODO: write docs
    Public variables and functions:
    
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diff --git a/docs/codox/intro.html b/docs/codox/intro.html
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-# Introduction to Wildwood
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+# Introduction to Wildwood
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    Introduction to Wildwood
    
 
    I started building Wildwood nearly forty years ago on InterLisp-D workstations. Then, because of changing academic projects, I lost access to those machines, and the project was effectively abandoned. But, I’ve kept thinking about it; it has cool ideas.
    
 
    Explicable inference
    
 
    Wildwood was a follow on from ideas developed in Arboretum, an inference system based on a novel propositional logic using defaults. Arboretum was documented in our paper
    
diff --git a/docs/codox/wildwood.core.html b/docs/codox/wildwood.core.html
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+++ b/docs/codox/wildwood.core.html
@@ -1,3 +1,3 @@
 
-wildwood.core documentation
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    wildwood.core
    TODO: write docs
    foo
    (foo x)
    I don’t do a whole lot.
    view source
    
\ No newline at end of file
+wildwood.core documentation
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    wildwood.core
    TODO: write docs
    foo
    (foo x)
    I don’t do a whole lot.
    view source
    
\ No newline at end of file
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@@ -0,0 +1,184 @@
+
+
+
+
+  
+    
+      
+    
+    
+      
+    
+  
+  
+    
+  
+  
+    
+      
+        image/svg+xml
+        
+        
+      
+    
+  
+  
+    
+    
+    D
+    So, Q, C
+    
+    
+    Since W
+    
+    on account of B
+    (after Toulmin, p 104; my emphasis of optional elements)
+  
+
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