Aristotle could have avoided the mistake of thinking that women have fewer teeth than men, by the simple device of asking Mrs. Aristotle to keep her mouth open while he counted.

When we perceive any object of a familiar kind, much of what appears subjectively to be immediately given is really derived from past experience.

Love is wise; hatred is foolish. In this world, which is getting more and more closely interconnected, we have to learn to tolerate each other, we have to learn to put up with the fact that some people say things that we don't like. We can only live together in that way. But if we are to live together, and not die together, we must learn a kind of charity and a kind of tolerance, which is absolutely vital to the continuation of human life on this planet.

Science is what you know, philosophy is what you don't know.

To the primitive mind, everything is either friendly or hostile; but experience has shown that friendliness and hostility are not the conceptions by which the world is to be understood.

Mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true.

All forms of fear produce fatigue.