What is the fundamental hypothesis of science, the fundamental philosophy? We stated it in the first chapter: the sole test of the validity of any idea is experiment. ... If we are told that the same experiment will always produce the same result, that is all very well, but if when we try it, it does not, then it does not. We just have to take what we see, and then formulate all the rest of our ideas in terms of our actual experience.

Phenomena complex-laws simple....Know what to leave out.

Just as a poet often has license from the rules of grammar and pronunciation, we should like to ask for 'physicists' license from the rules of mathematics in order to express what we wish to say in as simple a manner as possible.

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.

You see, I get such fun out of thinking that I don't want to destroy this most pleasant machine that makes life such a big kick.

I don't believe I can really do without teaching.

The test of all knowledge is experiment.