#### Supplement to Defeasible Reasoning

## 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*).