Man can be stimulated by hope or driven by fear, but the hope and the fear must be vivid and immediate if they are to be effective without producing weariness.

All the time that he can spare from the adornment of his person, he devotes to the neglect of his duties.

Do not feel certain of anything.

At the age of eleven, I began Euclid, with my brother as my tutor. ... I had not imagined that there was anything so delicious in the world. After I had learned the fifth proposition, my brother told me that it was generally considered difficult, but I had found no difficulty whatsoever. This was the first time it had dawned on me that I might have some intelligence.

To create a healthy philosophy you should renounce metaphysics but be a good mathematician.

The thing that I should wish to obtain from money would be leisure with security.

Freedom of opinion can only exist when the government thinks itself secure.