What was once thought can never be unthought.

If a man sits down to think, he is immediately asked if he has the headache.

Intellect annuls fate. So far as a man thinks, he is free.

Thought makes every thing fit for use.

To think is to act.

All thought is a feat of association: having what's in front of you bring up something in your mind that you almost didn't know you knew.

Those that think must govern those that toil.

Thinking is hard work. One can't bear burdens and ideas at the same time.

The secret thoughts of a man run over all things, holy, profane, clean, obscene, grave, and light, without shame or blame.

There is one disadvantage which the man of philosophical habits of mind suffers, as compared with the man of action. While he is taking an enlarged and rational view of the matter before him, he lets his chance slip through his fingers.