Science is what we have learned about how to keep from fooling ourselves.

There is no harm in doubt and skepticism, for it is through these that new discoveries are made.

I have argued flying saucers with lots of people. I was interested in possible. They do not appreciate that the problem is not to demonstrate whether it's possible or not but whether it's going on or not.

All mass is interaction.

If we want to solve a problem that we have never solved before, we must leave the door to the unknown ajar.

Ordinarily it would take me about fifteen minutes to get a hallucination going," wrote Feynman, "but on a few occasions, when I smoked some marijuana beforehand, it came very quickly.

If you thought that science was certain - well, that is just an error on your part.