Intellect, without heart, is infinitely cruel. . . .

I have no reverence for any book that teaches a doctrine contrary to my reason; no reverence for any book that teaches a doctrine contrary to my heart; and, no matter how old it is, no matter how many have believed it, no matter how many have died on account of it, no matter how many live for it, I have no reverence for that book, and I am glad of it.

Religion has not civilized man, man has civilized religion.

When a man really believes that it is necessary to do a certain thing to be happy forever, or that a certain belief is necessary to ensure eternal joy, there is in that man no spirit of concession. He divides the whole world into saints and sinners, into believers and unbelievers, into God's sheep and Devil's goats, into people who will be glorified and people who are damned.

For thousands of years people have been trying to force other people to think their way. Did they succeed? No. Will they succeed? No. Why? Because brute force is not an argument.

Labor is the only prayer that Nature answers.

Sacred are the lips from which has issued only truth.