It is a curious fact that of all the illusions that beset mankind none is quite so curious as that tendency to suppose that we are mentally and morally superior to those who differ from us in opinion.

Morality is the thing upon which your friends smile, and immorality is the thing upon which they frown

Be yourself and think for yourself, and while your conclusions may not be infallible they will be nearer right than the inclusions forced upon you by those who have a personal interest in keeping you in ignorance.

Progress needs the brakeman, but the brakeman should not spend all his time putting on the brakes.

In the Life of Darwin by his son, there is related an incident of how the great naturalist once studied long as to just what a certain spore was. Finally he said, "It is this, for if it isn't, then what is it?" And all during his life he was never able to forget that he had been guilty of this unscientific attitude, for science is founded on certitude, not assumption.

The only foes that threaten America are the enemies at home, and these are ignorance, superstition and incompetence.

Nature: The unseen intelligence which loved us into being, and is disposing of us by the same token