How the study of causality revolutionized science and the world Cause and effect: it's at the center of scientific inquiry, and yet for decades scientists had no way of answering simple questions, such as whether smoking causes cancer. In The Book of Why , Judea Pearl and Dana Mackenzie show how Pearl's work on causality has broken through this stalemate, unleashing a revolution in our knowledge of the world. Anyone who wants to understand how science, the human mind, or artificial intelligence works needs The Book of Why . "Illuminating. . . a valuable lesson on the history of ideas." -- New York Times "This book really gets you thinking about cause and effect as it applies to issues of our time. . . . Extraordinary." -- Science Friday