Wolfgang Spohn presents the first full account of the dynamic laws of belief, by means of ranking theory. This book is his long-awaited presentation of ranking theory and its ramifications. He motivates and introduces the basic notion of a ranking function, which recognises degrees of belief and at the same time accounts for belief simpliciter. He provides a measurement theory for ranking functions, accounts for auto-epistemology in ranking-theoretic terms, and explicates the basic notion of a (deductive or non-deductive) reason. The rich philosophical applications of Spohn's theory include:...