Only free men are thoroughly grateful one to another.

I have tried sedulously not to laugh at the acts of man, nor to lament them, nor to detest them, but to understand them.

Man can, indeed, act contrarily to the decrees of God, as far as they have been written like laws in the minds of ourselves or the prophets, but against that eternal decree of God, which is written in universal nature, and has regard to the course of nature as a whole, he can do nothing.

The highest endeavor of the mind, and the highest virtue, it to understand things by intuition.

Let unswerving integrity be your watchword.

In the mind there is no absolute or free will; but the mind is determined to wish this or that by a cause, which has also been determined by another cause, and this last by another cause, and so on to infinity.

Superstition, then, is engendered, preserved, and fostered by fear.