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C00002 00002	belief[f83,jmc]		Axioms for persistence of belief
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belief[f83,jmc]		Axioms for persistence of belief

We want to use  ab  and circumscription to formalize the persistence
of unchallenged beliefs.

1.	∀p t.¬ab aspect1(p,t) ⊃ ¬believe(p,t)
Normally a proposition isn't believed.

2.	∀p t t1.believed(p,t1) ∧ t1 < t ∧ (∀t2.t1≤t2≤t ⊃ ¬believed(not p,t2))
		⊃ ab aspect1(p,t)
(1) doesn't apply to propositions that were previously believed
and whose denial wasn't believed more recently.

3.	∀p t t1.believed(p,t1) ∧ t1 < t ∧ (∀t2.t1≤t2≤t ⊃ ¬believed(not p,t2))
		∧ ¬ab aspect2(p,t)
	⊃ believed(p,t)
Under the same conditions as (2), a proposition normally is believed.

	These axioms presume that  ab z  is to be circumscribed, but
since circumscription, as we presently know it, is expensive computationally,
we really propose that the same effect be obtained in some less
expensive way.  For now, however, circumscription defines the logic.