Why is our world comprehensible? This question seems so trivial that few people have dared to ask it. In this book we explore the deep roots of the mystery of rationality. The inquiry into the rationality of the world began over two-and-a-half-thousand years ago, when a few courageous people tried to understand the world with the help of reason alone, rejecting the comforting fabric of myth and legend.After many philosophical and theological adventures the Greek concept of rationality laid the foundations of a revolutionary way of thinking: the scientific method, which transformed the world.