Doctors use reason and probability to assess and treat patients. But given the complexity, uncertainty, and fast pace of real-world medical practice, physicians have no choice but to use mental shortcuts and probability estimates as they do their vital work. When doctors deeply understand how they reason, they improve their clinical decision making. This book teaches students, residents, and practicing physicians to think clearly about the logic, probability, and cognitive psychology of medical reasoning. Simple examples, visual explanations, and historical context make the art of how doctors think fascinating and highly relevant to daily medical practice. Reading this book will help you improve the care of your patients, one at a time.