Not all heads have a brain.

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

The brain may be regarded as a kind of parasite of the organism, a pensioner, as it were, who dwells with the body.

The mind is not, I know, a highway but a temple, and its doors should not be carelessly left open.

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.

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

Every thought is, strictly speaking, an afterthought.

Brain, n. An apparatus with which we think that we think.

What is the hardest task in the world? To think.

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

Sanity is madness put to good uses; waking life is a dream controlled.

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

Strength of mind is exercise, not rest.