English naturalist whose On the Origin of Species (1859) and The Descent of Man (1871) are the foundation of modern biology and, more pervasively, of the modern Western picture of the living world — including the human part of it. No 19th-century thinker, including Marx and Freud (both of whom acknowledged the debt), more thoroughly reshaped the categories in which the century that followed did its thinking. Darwin is therefore a presence in this knowledge graph less as a philosopher than as the source material most of its 19th- and 20th-century figures are responding to, knowingly or not.
The five-year Beagle voyage (1831–36) gave him the observations — the Galápagos finches, the South American fossil mammals, the geological evidence for a deeply old earth — that, over the next two decades of patient barnacle-dissecting and pigeon-breeding in the garden at Down House, became a single sustained argument: that the variety of living forms is the product of descent with modification through natural selection, a mechanism requiring no designer and no teleology. The argument is notorious for what it does not require (a creator, a goal, a hierarchy of beings) and for what it implies: that Homo sapiens is one species among millions, continuous with the rest of nature, and that the moral and cognitive capacities that seemed to set humans apart are themselves products of the same unguided process. The Descent of Man extended the framework to human evolution, including the evolution of the moral sense — a move for which Darwin was attacked in his lifetime and which remains under sustained theological and philosophical pressure.
His later books — on earthworms, on orchid pollination, on the expression of emotions — continued the patient, accumulating empirical work that was always his characteristic mode. He was a meticulous observer and a cautious, revising writer; the boldest thinker of his century was also its most constitutionally modest.