He who lives in the single exercise of his mental faculties, however usefully or curiously directed, is equally an imperfect animal with the man who knows only the exercise of muscles.

Instead of establishing facts, we have to overthrow errors; instead of ascertaining what is, we have to chase from our imaginations what is not.

You have heard of, and studied various systems of philosophy; but real philosophy is opposed to all systems.

Equality is the soul of liberty; there is, in fact, no liberty without it.

The sciences have ever been the surest guides to virtue.

All that I say is, examine, inquire. Look into the nature of things. Search out the grounds of your opinions, the for and against. Know why you believe, understand what you believe, and possess a reason for the faith that is in you.

The simplest principles become difficult of practice, when habits, formed in error, have been fixed by time, and the simplest truths hard to receive when prejudice has warped the mind.