What is best in mathematics deserves not merely to be learnt as a task, but to assimilated as a part of daily thought, and brought again and again before the mind with ever-renewed encouragement.

There is little of the true philosophic spirit in Aquinas. He does not, like the Platonic Socrates, set out to follow wherever the argument may lead.

You find as you look around the world that every single bit of progress in humane feeling, every improvement in the criminal law, every step toward the diminution of war, every step toward better treatment of the colored races, or every mitigation of slavery, every moral progress that there has been in the world, has been consistently opposed by the organized churches of the world. I say quite deliberately that the christian religion, as organized in its churches, has been and still is the principle enemy of moral progress in the world.

Civilized life, if it is to be stable, must provide a harmless outlets for the impulses which our remote ancestors satisfied in hunting. In Australia, where people are few, and rabbits are many, I watched the whole populace satisfying the primitive impulse in the primitive manner by the skilful slaughter of many thousands of rabbits.

It is clear that thought is not free if the profession of certain opinions makes it impossible to earn a living.

I would never die for my beliefs because I might be wrong.

There was a law in Connecticut - I believe it is still formally unrepealed - making it illegal for a man to kiss his wife on Sunday.