This book tells the story of Peter Cathcart Wason, offering unique insights into the life of the pioneering research psychologist credited for establishing a whole new field of science: the psychological study of reasoning. And this was just one of the major contributions he made to psychology. Covering much more than Wason’s academic work, the author, Ken Manktelow, paints a vivid and personal portrait of the man. The book traces Wason’s eclectic family history, steeped in Liberal politics and aristocratic antecedents, before moving through his service in the Second World War and the life-changing injuries he sustained at the end of it, and on to his abortive first attempt at a career and subsequent extraordinary success as a psychologist. Following a chronological structure with each chapter dedicated to a significant transition period in Wason’s life, Manktelow expertly weaves together personal narratives with Wason’s evolving intellectual interests and major scientific discoveries, and in doing so simultaneously traces the worlds that vanished during the twentieth century. A brilliant biography of one of the most renowned figures in cognitive psychology, this book will be of interest not only to students and scholars in thinking and reasoning, but to anyone interested in the life and lasting contribution of this celebrated scholar.