As is the face, so is the mind.

The real question is not whether machines think but whether men do.

Sooner or later if the activity of the mind is restricted anywhere, it will cease to function even where it is allowed to be free.

Understanding is a very dull occupation.

The brain is an unreliable organ, it is monstrously great, monstrously developed. Swollen, like a goiter.

The sleep of reason produces monsters.

The mind of man is capable of anything.

Your mind’s got to eat, too.

A mind lively and at ease can do with seeing nothing, and can see nothing that does not answer.

Strength of mind is exercise, not rest.

What a torture to talk to filled heads that allow nothing from the outside to enter them.

“I think, therefore I am” is the statement of an intellectual who underrates toothaches.

The universe is an object of thought at least as much as it is a means of satisfying needs.