Abstract

Neil Tennant (Tennant, 2005) has offered an important observation about the AGM theory of belief revision (G¨ardenfors, 1988). We attempt to restate and demonstrate his result in a slightly different way. Fix a formal language L that embeds sentential logic. Given K ⊆ L and ϕ ∈ L, K ⊥ ϕ denotes the class of maximally consistent subsets of K that do not imply ϕ. That is, A ∈ K ⊥ ϕ iff A ⊆ K, A |= ϕ, and there is no B ⊆ K such that B ⊃ A and..