As far as I'm concerned, I prefer silent vice to ostentatious virtue.

Only a life lived for others is a life worthwhile.

Teaching should be such that what is offered is perceived as a valuable gift and not as hard duty. Never regard study as duty but as the enviable opportunity to learn to know the liberating influence of beauty in the realm of the spirit for your own personal joy and to the profit of the community to which your later work belongs.

Science has gone a long way toward helping man to free himself from the burden of hard labor; yet, science itself is not a liberator. It creates means, not goals. It is up to men to utilize those means to achieve reasonable goals.

What is the meaning of human life, or, for that matter, of the life of any creature? To know the answer to this question means to be religious. You ask: Does it make any sense, then, to pose this question? I answer: The man who regards his fellow creatures as meaningless is not merely unhappy but hardly fit for life.

Anybody who really wants to abolish war must resolutely declare himself in favor of his own country's resigning a portion of sovereignty in place of international institutions.

Whether or not you can observe a thing depends upon the theory you use. It is the theory which decides what can be observed.