There is only one duty; that is to be happy.

Those who fear the facts will forever try to discredit the fact-finders.

I feel, I think, I judge; therefore, a part of organized matter like me is capable of feeling, thinking, and judging.

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.

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!

The arbitrary rule of a just and enlightened prince is always bad. His virtues are the most dangerous and the surest form of seduction: they lull a people imperceptibly into the habit of loving, respecting, and serving his successor, whoever that successor may be, no matter how wicked or stupid.

The man who first pronounced the barbarous word God ought to have been immediately destroyed.