Mild Contraction Evaluating Loss of Information Due to Loss of Belief

Isaac Levi's new book develops further his pioneering work in formal epistemology, focusing on the problem of belief contraction, or how rationally to relinquish old beliefs. Levi offers the most penetrating analysis to date of this key question in epistemology, offering a completely newsolution and explaining its relation to his earlier proposals. He mounts an argument in favour of the thesis that contracting a state of belief by giving up specific beliefs is to be evaluated in terms of the value of the information lost by doing so. The rationale aims to be thoroughly decisiontheoretic. Levi spells out his goals and shows that certain types of recommendations are obtained if one seeks to promote these goals. He compares his approach to his earlier account of inductive expansion. The recommendations are for 'mild contractions'. These are formally the same as the 'severewithdrawals' considered by Pagnucco and Rott. The rationale, however, is different. A critical part of the book concerns the elaboration of these differences. The results are relevant to accounts of the conditions under which it is legitimate to cease believing and to accounts of conditionals. MildContraction will be of great interest to all specialists in belief revision theory and to many students of formal epistemology, philosophy of science, and pragmatism.

Isaac Levi is John Dewey Professor Emeritus of Philosophy at Columbia University.