While differing widely in the various little bits we know, in our infinite ignorance we are all equal.

If you know that things are bound to happen whatever you do, then you may feel free to give up the fight against them.

It can't happen here is always wrong: a dictatorship can happen anywhere.

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.

No rational argument will have a rational effect on a man who does not want to adopt a rational attitude.

There is no pure, disinterested, theory-free observation.

Optimism is a duty. The future is open. It is not predetermined. No one can predict it, except by chance. We all contribute to determining it by what we do. We are all equally responsible for its success.