The demand for certainty is one which is natural to man, but is nevertheless an intellectual vice.

Ordinary language is totally unsuited for expressing what physics really asserts, since the words of everyday life are not sufficiently abstract. Only mathematics and mathematical logic can say as little as the physicist means to say.

To be without some of the things you want is an indispensable part of happiness.

This has been my life. I have found it worth living, and would gladly live it again if the second chance were offered me.

Awareness of universals is called conceiving, and a universal of which we are aware is called a concept.

It is clear that thought is not free if the profession of certain opinions makes it impossible to earn a living.

Those whose lives are fruitful to themselves, to their friends, or to the world are inspired by hope and sustained by joy: they see in imagination the things that might be and the way in which they are to be brought into existence.