To know what people really think, pay regard to what they do, rather than what they say.

I think, therefore I am.

The reading of all good books is like a conversation with the finest minds of past centuries.

In order to improve the mind, we ought less learn than to contemplate.

Illusory joy is often worth more than genuine sorrow.

I hope that posterity will judge me kindly, not only as to the things which I have explained, but also to those which I have intentionally omitted so as to leave to others the pleasure of discovery.

Except our own thoughts, there is nothing absolutely in our power.