"The use of conditional terms such as 'if' also distinguishes human intelligence from that of all other animals, permitting a higher level of rationality in human reasoning and decision making. Until now, conditionals have been the subject of independent study by psychologists and philosophers. In this volume, Jonathan Evans and David Over present a new theoretical approach to understanding hypothetical thought. The book draws on studies from the psychology of judgement and decision making, as well as philosophical logic." A new volume in the acclaimed Oxford Cognitive Science series, If will be an important book for both psychologists and philosophers interested in human reasoning.