I have not the hope of being immortal, because the desire of it has not given me that vanity.

Which is the greater merit, to enlighten the human race, which remains forever, or to save one's fatherland, which is perishable?

Fanaticism is just one step away from barbarism.

Does anyone really know where they're going to?

The most dangerous madmen are those created by religion, and people whose aim is to disrupt society always know how to make good use of them on occasion.

Anyone who takes it upon himself, on his private authority, to break a bad law, thereby authorizes everyone else to break the good ones.

As long as the centuries continue to unfold, the number of books will grow continually, and one can predict that a time will come when it will be almost as difficult to learn anything from books as from the direct study of the whole universe. It will be almost as convenient to search for some bit of truth concealed in nature as it will be to find it hidden away in an immense multitude of bound volumes.