There are two things that kill a genius - a fatal disease and contentment.

It’s not bad people I fear so much as good people. When a person is sure that he is good, he is nearly hopeless; he gets cruel- he believes in punishment.

One believes in the truthfulness of a man because of his long experience with the man, and because the man has always told a consistent story. But no man has told so consistent a story as nature.

If today you can take a thing like evolution and make it a crime to teach it in the public school, tomorrow you can make it a crime to teach it in the private schools, and the next year you can make it a crime to teach it to the hustings or in the church. At the next session you may ban books and newspapers. Soon you may set Catholic against Protestant and Protestant against Protestant, and try to foist your own religion upon the minds of men.

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.

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.

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