The dictum that human nature cannot be changed is one of those tiresome platitudes that conceal from the ignorant the depths of their own ignorance.

We ought to look the world frankly in the face.

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.

The true spirit of delight...is to be found in mathematics as surely as in poetry.

The secret of happiness is this: let your interests be as wide as possible, and let your reactions to the things and persons that interest you be as far as possible friendly rather than hostile.

The secrets to happiness include enterprise, exploration of one's interests and the overcoming of obstacles.

Our great democracies still tend to think that a stupid man is more likely to be honest than a clever man.