Now revised and updated, this introduction to decision theory is both accessible and comprehensive, covering topics including decision making under ignorance and risk, the foundations of utility theory, the debate over subjective and objective probability, Bayesianism, causal decision theory, game theory, and social choice theory. No mathematical skills are assumed, with all concepts and results explained in non-technical and intuitive as well as more formal ways. There are now over 140 exercises with solutions, along with a glossary of key terms and concepts. This second edition includes a new chapter on risk aversion as well as updated discussions of numerous central ideas, including Newcomb's problem, prisoner's dilemmas, and Arrow's impossibility theorem. The book will appeal particularly to philosophy students but also to readers in a range of disciplines, from computer science and psychology to economics and political science. A comprehensive and accessible introduction to all aspects of decision theory, now with new and updated discussions and over 140 exercises. Martin Peterson holds the Sue and Harry Bovay Chair in the Department of Philosophy, Texas A&M University. He is the author of several books on decision theory, ethics, and risk, including Non-Bayesian Decision Theory (2008), The Dimensions of Consequentialism (Cambridge, 2013), and The Ethics of Technology (forthcoming).