They must often change, who would be constant in happiness or wisdom. Those who continually search for happiness will never find it. Happiness is made, not found. To be without some of the things you want is an indispensable part of happiness.

[There are m]oral precepts that we consider really important, such as 'don't pick your nose' or 'don't eat peas with a knife'. There may, for ought I know, be admirable reasons for eating peas with a knife, but . . . early persuasion has made me completely incapable of appreciating them.

The main thing needed to make men happy is intelligence.

Arithmetic must be discovered in just the same sense in which Columbus discovered the West Indies, and we no more create numbers than he created the Indians.

Science is what we know, and philosophy is what we don't know.

Even in civilized mankind faint traces of monogamous instinct can be perceived.

The governors of the world believe, and have always believed, that virtue can only be taught by teaching falsehood, and that any man who knew the truth would be wicked. I disbelieve this, absolutely and entirely. I believe that love of truth is the basis of all real virtue, and that virtues based upon lies can only do harm.