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

Madness need not be all breakdown. It may also be breakthrough.

What is outside my mind means nothing to it.

The march of the human mind is slow.

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

As is the face, so is the mind.

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.

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

It is far, far better and much safer to have a firm anchor in nonsense than to put out on the troubled seas of thought.

From a man’s face, I can read his character. If I can see him walk, I know his thoughts.

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

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

What the brain does by itself is infinitely more fascinating and complex than any response it can make to chemical stimulation.