Thought is action in rehearsal.

It's true of all of us ... We think too much.

The fundamental fact about the Greek was that he had to use his mind. The ancient priests had said, "Thus far and no further. We set the limits of thought." The Greeks said, "All things are to be examined and called into question. There are no limits set on thought."

Never be afraid to sit awhile and think.

Every man has special thoughts of his own, rivaling the best literature of any nation.

A thought must tell at once, or not at all.

The essence of life consists in thinking, and being conscious of one's soul.

Vigilantly guard your mind against erroneous and destructive thought as you would guard your house against burglars and assassins.

You talk to yourself all the time, be careful what you say. Negative images are destructive.

Think wrongly, if you please, but in all cases think for yourself.