The real doubt is the doubt that doubts that it doubts.

God is a questioner; Man is a philosopher.

If I am convinced that I will procure the profoundest idea only by undergoing the profoundest pain, I shall beg for strength to endure that pain.

Solitude is unquenched ego.

I speculate that this is the best of all possible worlds, for philosophy is the best of humanity, and this world is the best philosophically.

Every noble action is selfish. Some selfish actions are nobler than others. But they are all selfish. And as such there can be no action purely noble anyway. Even the nobility in God's great philosophical intentions is bounded by his vanity.

The worst of all superstitions may be that astrology is a superstition.