Denis Diderot is often associated with the decades-long battle to bring the world's first comprehensive Encyclopedie into existence. But his most daring writing took place in the shadows. In the astonishing cache of unpublished writings left behind after his death, Diderot dreamed of natural selection before Darwin, the Oedipus complex before Freud, and genetic manipulation centuries before Dolly the Sheep. Even more audaciously, the writer challenged virtually all of his century's accepted truths, from the sanctity of monarchy, to the racial justification of the slave trade, to the complications of human sexuality.