I do not say think as I think, but think in my way. Fear no shadows, least of all in that great spectre of personal unhappiness which binds half the world to orthodoxy.

To say that an idea is necessary is simply to affirm that we cannot conceive the contrary; and the fact that we cannot conceive the contrary of any belief may be a presumption, but is certainly no proof, of its truth.

There is no sadder sight in the world than to see a beautiful theory killed by a brutal fact.

Do what you can to do what you ought, and leave hoping and fearing alone.

No delusion is greater than the notion that method and industry can make up for lack of mother-wit, either in science or in practical life.

Only a scientific people can survive in a scientific future.

Extinguished theologians lie about the cradle of every science as the strangled snakes beside that of Hercules; and history records that whenever science and orthodoxy have been fairly opposed, the latter has been forced to retire from the lists, bleeding and crushed if not annihilated; scotched, if not slain.