It has been said that man is a rational animal. All my life I have been searching for evidence which could support this.

By three methods we may learn wisdom: First, by reflection, which is noblest; Second, by imitation, which is easiest; and third by experience, which is the bitterest.

Silence is argument carried out by other means.

A physicist is an atom's way of knowing about atoms.

Thoughts without content are empty, intuitions without concepts are blind.

New opinions are always suspected, and usually opposed, without any other reason but because they are not already common.

Nothing is more honorable than enlightenment, nothing is more beautiful than virtue.

Wise men are instructed by reason; men of less understanding, by experience; the most ignorant, by necessity; the beasts, by nature.

How wonderful that we have met with paradox. Now we have some hope of making progress.

If there were in the world today any large number of people who desired their own happiness more than they desired the unhappiness of others, we could have paradise in a few years.