diff --git a/src/beowulf/bootstrap.clj b/src/beowulf/bootstrap.clj
index 3b69d49..ade18df 100644
--- a/src/beowulf/bootstrap.clj
+++ b/src/beowulf/bootstrap.clj
@@ -11,7 +11,7 @@
   objects."
   (:require [clojure.string :as s]
             [clojure.tools.trace :refer [deftrace]]
-            [beowulf.cons-cell :refer [make-beowulf-list make-cons-cell NIL T F]]))
+            [beowulf.cons-cell :refer [cons-cell? make-beowulf-list make-cons-cell NIL pretty-print T F]]))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;
@@ -38,6 +38,11 @@
   [x]
   `(if (= ~x NIL) T F))
 
+(defmacro NILP
+  "Not part of LISP 1.5: `T` if `o` is `NIL`, else `NIL`."
+  [x]
+  `(if (= ~x NIL) T NIL))
+
 (defmacro ATOM
   "Returns `T` if and only if the argument `x` is bound to an atom; else `F`.
   It is not clear to me from the documentation whether `(ATOM 7)` should return
@@ -280,6 +285,16 @@
        "/")))
     l))
 
+(defn to-beowulf
+  "Return a beowulf-native representation of the Clojure object `o`.
+  Numbers and symbols are unaffected. Collections have to be converted;
+  strings must be converted to symbols."
+  [o]
+  (cond
+    (coll? o) (make-beowulf-list o)
+    (string? o) (symbol (s/upper-case o))
+    :else o))
+
 (defn to-clojure
   "If l is a `beowulf.cons_cell.ConsCell`, return a Clojure list having the 
   same members in the same order."
@@ -359,6 +374,33 @@
       {:cause  :interop
        :detail :strict}))))
 
+(defn OBLIST
+  "Not certain whether or not this is part of LISP 1.5; adapted from PSL. 
+  return the current value of the object list. Note that in PSL this function
+  returns a list of the symbols bound, not the whole association list."
+  [args]
+  (@oblist))
+
+(deftrace DEFINE
+  "Bootstrap-only version of `DEFINE` which, post boostrap, can be overwritten 
+  in LISP. 
+
+  The single argument to `DEFINE` should be an assoc list which should be 
+  nconc'ed onto the front of the oblist. Broadly, 
+  (SETQ OBLIST (NCONC ARG1 OBLIST))"
+  [args]
+  (swap!
+   oblist
+   (fn [ob arg1]
+     (loop [cursor arg1 a arg1]
+       (if (= (CDR cursor) NIL)
+         (do
+           (.rplacd cursor @oblist)
+           (pretty-print a)
+           a)
+         (recur (CDR cursor) a))))
+     (CAR args)))
+
 (defn APPLY
   "For bootstrapping, at least, a version of APPLY written in Clojure.
   All args are assumed to be symbols or `beowulf.cons-cell/ConsCell` objects.
@@ -373,6 +415,7 @@
           (= function 'CAR) (CAAR args)
           (= function 'CDR) (CDAR args)
           (= function 'CONS) (make-cons-cell (CAR args) (CADR args))
+          (= function 'DEFINE) (DEFINE args)
           (= function 'ATOM) (if (ATOM? (CAR args)) T NIL)
           (= function 'EQ) (if (= (CAR args) (CADR args)) T NIL)
           (= function 'INTEROP) (INTEROP (CAR args) (CDR args))
@@ -381,6 +424,8 @@
            (EVAL function environment)
            args
            environment))
+    (fn? function) ;; i.e., it's a Clojure function
+    (apply function (to-clojure args))
     (= (first function) 'LAMBDA) (EVAL
                                   (CADDR function)
                                   (PAIRLIS (CADR function) args environment))
@@ -424,9 +469,9 @@
                      (throw
                       (ex-info
                        (str "EVAL: strings not allowed in strict mode: \"" expr "\"")
-                      {:cause  :eval
-                       :detail :strict
-                       :expr   expr}))
+                       {:cause  :eval
+                        :detail :strict
+                        :expr   expr}))
                      (symbol expr))
     (= (ATOM? expr) T) (CDR (ASSOC expr env))
     (=
diff --git a/src/beowulf/cons_cell.clj b/src/beowulf/cons_cell.clj
index f99f4f2..f15106e 100644
--- a/src/beowulf/cons_cell.clj
+++ b/src/beowulf/cons_cell.clj
@@ -4,6 +4,8 @@
   must have both CAR and CDR mutable, so cannot be implemented on top
   of Clojure lists.")
 
+(declare cons-cell?)
+
 (def NIL
   "The canonical empty list symbol."
   (symbol "NIL"))
@@ -46,6 +48,7 @@
               ;; beowulf.cons_cell.ConsCell,
               ;; because it is not yet
               ;; defined
+      (cons-cell? value)
       (number? value)
       (symbol? value))
       (do
@@ -60,6 +63,7 @@
     (if
      (or
       (satisfies? MutableSequence value)
+      (cons-cell? value)
       (number? value)
       (symbol? value))
       (do
@@ -217,6 +221,11 @@
        (throw (ex-info "Cound not construct cons cell" {:car car
                                                         :cdr cdr} any)))))
 
+(defn cons-cell?
+  "Is this object `o` a beowulf cons-cell?"
+  [o]
+  (instance? beowulf.cons_cell.ConsCell o))
+
 (defn make-beowulf-list
   "Construct a linked list of cons cells with the same content as the
   sequence `x`."