'But,' I [Dmitri Karamazov] asked, 'how will man be after that? Without God and the future life? It means everything is permitted now, one can do anything?' 'Didn't you know?' he said. And he laughed. 'Everything is permitted to the intelligent man,' he said.

Book XI, ch. 4 (trans. Pevear and Volokhonsky). - The Brothers Karamazov (1879–1880)