Our theories of the eternal are as valuable as are those which a chick which has not broken its way through its shell might form of the outside world

The theory seems to be that as long as a man is a failure he is one of God's children, but that as soon as he succeeds he is taken over by the Devil.

Theory helps us to bear our ignorance of facts

If Darwin's theory should be true, it will not degrade man; it will simply raise the whole animal world into dignity, leaving man as far in advance as he is at present

There is a theory which states that if ever for any reason anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened

Thought and theory must precede all salutary action; yet action is nobler in itself than either thought or theory

An ounce of action is worth a ton of theory