But this long history of learning how to not fool ourselves — of having utter scientific integrity — is, I’m sorry to say, something that we haven’t … - Richard Feynman

"The first person you should be careful not to fool is yourself. Because you are the easiest person to fool".

The first principle is that you must not fool yourself — and you are the easiest person to fool. So you have to be very careful about that. After you’ve not fooled yourself, it’s easy not to fool other scientists. You just have to be honest in a conventional way after that.

Science is a way of trying not to fool yourself. The principle is that you must not fool yourself, and you are the easiest person to fool.

You must not fool yourself — and you are the easiest person to fool.

The first principle is that you must not fool yourself — and you are the easiest person to fool.

The first principle is that you must not fool yourself, and you are the easiest person to fool.

In general, we look for a new law by the following process: First we guess it. Then we – now don't laugh, that's really true. Then we compute the consequences of the guess to see what, if this is right, if this law that we guessed is right, to see what it would imply. And then we compare the computation results to nature, or we say compare to experiment or experience, compare it directly with observations to see if it works. If it disagrees with experiment, it's wrong. In that simple statement is the key to science. It doesn't make any difference how beautiful your guess is, it doesn't make any difference how smart you are, who made the guess, or what his name is. If it disagrees with experiment, it's wrong. That's all there is to it.

"It is interesting that this thoroughness, which is a virtue, is often misunderstood. When someone says a thing has been done scientifically, often all he means is that it has been done thoroughly. I have heard people talk of the "scientific" extermination of the Jews in Germany. There was nothing scientific about it. It was only thorough. There was no question of making observations and then checking them in order to determine something. In that sense, there were "scientific" exterminations of people in Roman times and in other periods when science was not so far developed as it is today and not much attention was paid to observation. In such cases, people should say "thorough" or "thoroughgoing," instead of "scientific.

All mass is interaction.