Charles Darwin was an English naturalist whose account of evolution by natural selection is among the most consequential ideas ever proposed, and whose philosophical implications are still being worked through.

The argument

On the Origin of Species (1859) rests on three observations and one inference. Organisms vary. Some variation is heritable. More are born than can survive. Therefore variations that help an organism survive and reproduce become more common over generations.

The mechanism requires no foresight and no goal. What looks designed is the accumulated residue of differential survival.

Why philosophy had to respond

The design argument. Before Darwin, the appearance of purpose in organisms was the strongest argument for a designer, and Hume's attack on it had lacked an alternative explanation. Darwin supplied one. See natural theology.

Teleology. Aristotelian final causes had survived in biology long after physics abandoned them, because hearts obviously seemed to be for something. Natural selection explains that language without purposes: a heart is for pumping blood because pumping blood is why hearts were selected. See telos.

Human nature. The Descent of Man (1871) placed humans inside the same process, which unsettled accounts of morality, reason and the soul that had assumed a discontinuity.

What it does not settle

Darwin explains how complexity arises, not why there is anything at all — the cosmological argument is untouched. And the naturalistic fallacy applies with force: that a trait was selected says nothing about whether it is good. Evolutionary claims about ethics routinely slide across the is-ought gap, which is a mistake about logic rather than about biology.