(?x)
&gt; &gt;         (&lt;=&gt; (Physical ?x)
&gt; &gt;              (exists (?y ?z)
&gt; &gt;                      (and (located-at ?x ?y)
&gt; &gt;                           (exists-at ?x ?z)))))
&gt; &gt;
&gt; &gt; (documentation "THEOREM:  Abstract and Physical are disjoint.")
&gt; &gt;
&gt; &gt; (disjoint Abstract Physical)
&gt; &gt;
&gt; &gt; ;; Proof: Immediate from the axioms for Abstract and Physical.
&gt; &gt;
&gt; &gt; (documentation "AXIOM: An independent entity need not bear the "has" 
&gt; r