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.

What did you ASK at school today?

You do not know anything until you have practiced.

If the professors of English will complain to me that the students who come to the universities, after all those years of study, still cannot spell 'friend,' I say to them that something's the matter with the way you spell friend.

We need to teach how doubt is not to be feared but welcomed. It's OK to say, "I don't know."

The test of all knowledge is experiment. Experiment is the sole judge of scientific truth.

I don't feel frightened by not knowing things, by being lost in the mysterious universe without any purpose - which is the way it really is, as far as I can tell. Possibly. It doesn't frighten me.