"The Sirian resumed his discussion with the little mites. He spoke to them with great kindness, although in the depths of his heart he was a little angry that the infinitely small had an almost infinitely great pride."
Voltaire was a great freethinker of his day. He wasn't an atheist - more of a deist actually. Although if he had known modern cosmology (e.g. Big Bang), I believe he may have become a fully fledged atheist. Around 1752 he composed one of the first science fiction short stories, Micromégas, about an inhabitant of Sirius who first made friends with a philosopher from Saturn.