Men have called me mad; but the question is not yet settled, whether madness is or is not the loftiest intelligence.

I have always regarded that Constitution as the most remarkable work known to me in modern times to have been produced by the human intellect, at a single stroke (so to speak), in its application to political affairs.

It is not reason which is the guide of life, but custom.

The test of a first-rate intelligence is the ability to hold two opposed ideas in the mind at the same time, and still retain the ability to function.

In walking, the will and the muscles are so accustomed to working together and performing their task with so little expenditure of force that the intellect is left comparatively free.

I've always felt that a person's intelligence is directly reflected by the number of conflicting points of view he can entertain simultaneously on the same topic.

To criticize is to appreciate, to appropriate, to take intellectual possession, to establish in fine a relation with the criticized thing and to make it one's own.

Intelligent people tend to have less friends than the average person. The smarter you are, the more selective you become.