Over two millennia ago, a Greek philosopher had a number of wondrous insights that paved the way to cosmology, physics, geography, meteorology and biology, setting in motion a new way of seeing the world. Anaximander's legacy includes the revolutionary idea that the earth floats in a void, that the world can be understood in natural rather than supernatural terms, that animals evolved, and that universal laws govern all phenomena. He introduced a new mode of rational thinking with an openness to uncertainty and to the progress of knowledge. In this elegant work, acclaimed physicist Carlo Rovelli brings to light the importance of Anaximander's overlooked legacy to modern science. He examines Anaximander as a scientist interested in shedding light on the deep nature of scientific thinking, which Rovelli locates in his rebellious ability to reimagine the world again and again. Anaximander celebrates the radical lack of certainty that defines the scientific quest for knowledge.