In its efforts to learn as much as possible about nature, modern physics has found that certain things can never be "known" with certainty. Much of our knowledge must always remain uncertain. The most we can know is in terms of probabilities.

Looking back at the worst times, it always seems that they were times in which there were people who believed with absolute faith and absolute dogmatism in something. And they were so serious in this matter that they insisted that the rest of the world agree with them. And then they would do things that were directly inconsistent with their own beliefs in order to maintain that what they said was true.

It is the facts that matter, not the proofs. Physics can progress without the proofs, but we can't go on without the facts ... if the facts are right, then the proofs are a matter of playing around with the algebra correctly.

I don't believe I can really do without teaching. The reason is, I have to have something so that when I don't have any ideas and I'm not getting anywhere, I can say to myself, "At least I'm living; at least I'm doing something. I'm making some contribution." It's just psychological.

In those days, in Far Rockaway, there was a youth center for Jewish kids at the temple.... Somebody nominated me for president of the youth center. The elders began getting nervous, because I was an avowed atheist by that time.... I thought nature itself was so interesting that I didn't want it distorted like that. And so I gradually came to disbelieve the whole religion.

Don't think about what you want to be, but what you want to do. Keep up some kind of a minimum with other things so that society doesn't stop you from doing anything at all.

Nature does not care what we call it, she just keeps on doing it.