The test of all knowledge is experiment.

You see, the chemists have a complicated way of counting: instead of saying "one, two, three, four, five protons", they say, "hydrogen, helium, lithium, beryllium, boron."

There is a computer disease that anybody who works with computers knows about. It's a very serious disease and it interferes completely with the work. The trouble with computers is that you 'play' with them!

I think I can safely say that nobody understands Quantum Mechanics.

Once we were driving in the midwest and we pulled into a McDonald's. Someone came up to me and asked me why I have Feynman diagrams all over my van. I replied, "Because I am Feynman!" The young man went, "Ahhhhh!"

One of the ways of stopping science would be only to do experiments in the region where you know the law. But experimenters search most diligently, and with the greatest effort, in exactly those places where it seems most likely that we can prove our theories wrong. In other words, we are trying to prove ourselves wrong as quickly as possible, because only in that way can we find progress.

The unanswerable mysteries... the attitude that all is uncertain... to summarize it - the humility of the intellect.