Whatever we know without inference is mental.

As soon as we abandon our own reason, and are content to rely upon authority, there is no end to our troubles.

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.

But courage in fighting is by no means the only form, nor perhaps even the most important. There is courage in facing poverty, courage in facing derision, courage in facing the hostility of one's own herd. In these, the bravest soldiers are often lamentably deficient. And above all there is the courage to think calmly and rationally in the face of danger, and to control the impulse of panic fear or panic rage.

Science can teach us, and I think our hearts can teach us, no longer to look around for imaginary supporters, no longer to invent allies in the sky, but rather to look to our own efforts here below to make the world a fit place to live.

When Benjamin Franklin invented the lightning-rod, the clergy, both in England and America, with enthusiastic support of George III, condemned it as an impious attempt to defeat the will of God.

Joy of life... depends upon a certain spontaneity in regard to sex. Where sex is repressed, only work remains, and a gospel of work for work's sake never produced any work worth doing.