Definitions.... are never really needed, and rarely of any use

We have become makers of our fate when we have ceased to pose as its prophets.

Ignorance is not a simple lack of knowledge but an active aversion to knowledge, the refusal to know, issuing from cowardice, pride, or laziness of mind.

The growth of knowledge depends entirely upon disagreement.

Philosophy is a necessary activity because we, all of us, take a great number of things for granted, and many of these assumptions are of a philosophical character; we act on them in private life, in politics, in our work, and in every other sphere of our lives -- but while some of these assumptions are no doubt true, it is likely, that more are false and some are harmful. So the critical examination of our presuppositions -- which is a philosophical activity -- is morally as well as intellectually important.

Every discovery contains an irrational element or a creative intuition.

I don't know whether God exists or not. ... Some forms of atheism are arrogant and ignorant and should be rejected, but agnosticism—to admit that we don't know and to search—is all right. ... When I look at what I call the gift of life, I feel a gratitude which is in tune with some religious ideas of God. However, the moment I even speak of it, I am embarrassed that I may do something wrong to God in talking about God.