There's a bit of testicle at the bottom of our most sublime feelings and our purest tenderness.

But if you will recall the history of our civil troubles, you will see half the nation bathe itself, out of piety, in the blood of the other half, and violate the fundamental feelings of humanity in order to sustain the cause of God: as though it were necessary to cease to be a man in order to prove oneself religious!

I picture the vast realm of the sciences as an immense landscape scattered with patches of dark and light. The goal towards which we must work is either to extend the boundaries of the patches of light, or to increase their number. One of these tasks falls to the creative genius; the other requires a sort of sagacity combined with perfectionism.

What has not been examined impartially has not been well examined. Skepticism is therefore the first step towards truth.

Scepticism is the first step towards truth.

You live as if you were destined to live forever, no thought of your frailty ever enters your head, of how much time has already gone by you take no heed. You squander time as if you drew from a full and abundant supply, so all the while that day which you bestow on some person or thing is perhaps your last. You have all the fears of mortals and all the desires of immortals… What foolish forgetfulness of mortality to defer wise resolutions to the fiftieth or sixtieth year, and to intend to begin life at a point to which few have attained.

Passions destroy more prejudices than philosophy does.