In the eighteenth century, two men dedicated their lives to the same daunting task: identifying and describing all life on Earth. Their approaches, however, could not have been more different. Carl Linnaeus, a pious Swedish doctor with a huckster’s flair, believed that life belonged in tidy, static categories. Georges-Louis de Buffon, an aristocratic polymath and keeper of France’s royal garden, viewed life as a dynamic swirl of complexities. Both began believing their task to be difficult, but not impossible. The rivalry between these two unique, driven individuals created reverberations that still echo today. Linnaeus gave the world such concepts as mammal, primate, and homo sapiens—but he also denied species change and promulgated racist pseudo-science. Buffon coined the term reproduction, formulated early prototypes of evolution and genetics, and argued passionately against prejudice.