belief revision the process by which cognitive states change in light of new information. This topic looms large in discussions of Bayes’s Theorem and other approaches in decision theory. The reasons prompting belief revision are characteristically epistemic; they concern such notions as quality of evidence and the tendency to yield truths. Many different rules have been proposed for updating one’s belief set. In general, belief revision typically balances risk of error against information increase. Belief revision is widely thought to proceed either by expansion or by conceptual revision. Expansion occurs in virtue of new observations; a belief is changed, or a new belief established, when a hypothesis (or provisional belief) is supported by evidence whose probability is high enough to meet a favored criterion of epistemic warrant. The hypothesis then becomes part of the existing belief corpus, or is sufficient to prompt revision. Conceptual revision occurs when appropriate changes are made in theoretical assumptions – in accordance with such principles as simplicity and explanatory or predictive power – by which the corpus is organized. In actual cases, we tend to revise beliefs with an eye toward advancing the best comprehensive explanation in the relevant cognitive domain. See also BAYESIAN RATIO- NALITY, COHERENTISM, EPISTEMOLOGY, FOUN- DATIONALISM , REFLECTIVE EQUILIBRIU.
J.D.T.