Date: Friday, 7th November, 2pm Location: E6A room 357 Speaker: Dr. Lee Flax Title: Three Uses of The Boolean Algebra of Sentences Abstract: A Boolean algebra of sets of sentences is described. Its elements are sets of first-order sentences and its operations are conjunction, disjunction and negation; its Boolean partial order relation is entailment. This cannot be done in a straightforward manner with ordinary first-order logic, so we need to constrain the language to make it all work. We do this by limiting the the vocabulary of the language, keeping it finite, and by limiting the depth of quantification and formation of terms. Using this Boolean algebra we can a) give an account of belief contraction that is equivalent to the usual AGM approach, b) give an account of nonmonotonic entailment (in the context of belief revision) and c) model some cognitive processes.