A thing is not proved just because no one has ever questioned it. What has never been gone into impartially has never been properly gone into. Hence scepticism is the first step toward truth. It must be applied generally, because it is the touchstone.
Denis DiderotIf reason be a gift of Heaven, and we can say as much of faith, Heaven has certainly made us two gifts not only incompatible, but in direct contradiction to each other. In order to solve the difficulty, we are compelled to say either that faith is a chimera or that reason is useless.
Denis DiderotIf there were a reason for preferring the Christian religion to natural religion, it would be because the former offers us, on the nature of God and man, enlightenment that the latter lacks. Now, this is not at all the case; for Christianity, instead of clarifying, gives rise to an infinite multitude of obscurities and difficulties.
Denis Diderot