Authentic reflection on scientific thought, the present book, written in a clear and pleasant way by one of the great theoretical physicists of our time, illustrates the depth of the process of rethinking our image of the world: a search for knowledge based on rebellion against the evidence. How did the Greeks discover that the Earth floats in space? Or that there is still heaven also under our feet? Who came to imagine it this way and how did it succeed? This effort to "reinvent the world", a central aspect of the scientific search for knowledge, did not begin with the Newtonian synthesis or the pioneering experiences of Galileo, nor with the first mathematical models of Alexandrian astronomy. It began much earlier, with what should be called the first great "scientific revolution" in the history of humanity: Anaximander's revolution. The man who took that great step is the protagonist of the following pages: Anaximander, born twenty-six centuries ago in the Greek city of Miletus, on the western coast of present-day Turkey. He is the origin of a radical conceptual transformation in science itself as we know it.