We absolutely must leave room for doubt or there is no progress and there is no learning. There is no learning without having to pose a question. And a question requires doubt. People search for certainty. But there is no certainty. People are terrified — how can you live and not know? It is not odd at all. You only think you know, as a matter of fact. And most of your actions are based on incomplete knowledge and you really don’t know what it is all about, or what the purpose of the world is, or know a great deal of other things. It is possible to live and not know.

If we will only allow that, as we progress, we remain unsure, we will leave opportunities for alternatives.

If you think you understand quantum mechanics, you don't understand quantum mechanics.

The basis of action on love, the brotherhood of all men, the value of the individual... the humility of the spirit.

For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.

No man is rich who is unsatisfied, but who wants nothing possess his heart's desire.

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!"