Defeasible Reasoning > AGM Postulates (Stanford Encyclopedia of Philosophy/Fall2006 Edition)

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AGM Postulates

Where K is a belief state, K*A represents the set of beliefs resulting from revising K with new belief A.

(K*1) K*A is closed under logical consequence.
(K*2) A belongs to K*A.
(K*3) K*A is a subset of the logical closure of K ∪ {A}.
(K*4) If ¬A does not belong to K, then the closure of K ∪ {A} is a subset of K*A.
(K*5) If K*A is logically inconsistent, then either K is inconsistent, or A is.
(K*6) If A and B are logically equivalent, then K*A = K*B.
(K*7) K*(A & B) is a subset of the logical closure of K*A ∪ {B}.
(K*8) If ¬B does not belong to K*A, then the logical closure of K*A ∪ B is a subset of K*(A & B).