Hypothetical thought involves the imagination of possibilities and the exploration of their consequences by a process of mental simulation. In this Classic Edition, Jonathan St B T Evans’ presents his pioneering Hypothetical Thinking Theory; an integrated theoretical account of a wide range of psychological studies on hypothesis testing, reasoning, judgement and decision making. Hypothetical Thinking Theory is built on three key principles and implemented in a version of Evans' well-known heuristic–analytic theory of reasoning. The central claim of this book is that this theory can provide an integrated account of apparently diverse phenomena including confirmation bias in hypothesis testing, acceptance of fallacies in deductive reasoning, belief biases in reasoning and judgement, biases of statistical judgement and numerous characteristic findings in the study of decision making. Featuring a reflective and insightful new introduction to the book, this classic edition discusses contemporary theory on cognitive biases, human rationality and dual-process theories of higher cognition. It will be of great interest to researchers, post graduates as well as advanced undergraduate students.