The fear of God is not the beginning of wisdom. The fear of God is the death of wisdom. Skepticism and doubt lead to study and investigation, and investigation is the beginning of wisdom.

Every one knows that the heavenly bodies move in certain paths in relation to each other with seeming consistency and regularity which we call [physical] law. ... No one attributes freewill or motive to the material world. Is the conduct of man or the other animals any more subject to whim or choice than the action of the planets? ... We know that man's every act is induced by motives that led or urged him here or there; that the sequence of cause and effect runs through the whole universe, and is nowhere more compelling than with man.

Education was in danger from the source that always hampered it—religious fanaticism.

The objector and the rebel who raises his voice against what he believes to be the injustice of the present and the wrongs of the past is the one who hunches the world along.

Everyone is the heir to all that has gone before; his structure and emotional life is fixed, and no two children of nature have the same heredity. I believe everyone should and must live out what is in him. So no two lives can be the same.

For to know all is to understand all, and this leaves no room for judgment and condemnation.

I feel as I always have, that the earth is the home and the only home of man, and I am convinced that whatever he is to get out of his existence he must get while he is here.