Life is too short to occupy oneself with the slaying of the slain more than once.

If every man possessed everything he wanted, and no one had the power to interfere with such possession; or if no man desired thatwhich could damage his fellow-man, justice would have no part to play in the universe.

Nothing great in science has ever been done by men, whatever their powers, in whom the divine afflatus of the truth-seeker was wanting.

Teach a child what is wise, that is morality. Teach him what is wise and beautiful, that is religion!

What men of science want is only a fair day's wages for more than a fair day's work.

Each such answer to the great question, invariably asserted by the followers of its propounder, if not by himself, to be complete and final, remains in high authority and esteem, it may be for one century, or it may be for twenty: but, as invariably, Time proves each reply to have been a mere approximation to the truth tolerable chiefly on account of the ignorance of those by whom it was accepted, and wholly intolerable when tested by the larger knowledge of their successors.

If there is anything in the world which I do firmly believe in, it is the universal validity of the law of causation.