Our freedom to doubt was born out of a struggle against authority in the early days of science. It was a very deep and strong struggle: permit us to … - Richard Feynman

Finally, I must tell you what the arrow is for the net result. When a thing can happen in alternative ways you do what we call "add the arrows"... I know how to add numbers. How do you add arrows? The rule is... you simply put one arrow head on the tail of the other... I just draw the second arrow off from the first one... exactly parallel... it's drawn the same, but it's centered, it's moved... it's tied one onto the other, head to tail, and the result, it's supposed to be the sum. The adding is this net arrow that you would get, from where you started [from the beginning of the first arrow] to where you ended [at the end of the second arrow]. The way of thinking of it, that is rather nice, is to think of each arrow as indicating the direction of a step to be taken. If we take a step, on this plane, this way [the distance and direction of arrow #1] and then take a step that way [the distance and direction of arrow #2] and we say, where did we actually move? We could have done it all in one step, this one [from the beginning of arrow #1 to the end of arrow #2]. So this is the one step which is the equivalent of the succession of the other steps. Adding means putting together steps... The square of the [summation] arrow determines the probability of the reflection.

I went for a walk outside. Maybe I was fooling myself, but I was surprised how I didn’t feel what I thought people would expect to feel under the circumstances. I wasn’t delighted, but I didn’t feel terribly upset, perhaps because I had known for seven years that something like this was going to happen. I didn’t know how I was going to face all my friends up at Los Alamos. I didn’t want people with long faces talking to me about it. When I got back (yet another tire went flat on the way), they asked me what happened. “She’s dead. And how’s the program going?” They caught on right away that I didn’t want to moon over it. (I had obviously done something to myself psychologically: Reality was so important — I had to understand what really happened to Arlene, physiologically — that I didn’t cry until a number of months later, when I was in Oak Ridge. I was walking past a department store with dresses in the window, and I thought Arlene would like one of them. That was too much for me.)

"There was a Princess Somebody of Denmark sitting at a table with a number of people around her, and I saw an empty chair at their table and sat down.
She turned to me and said, "Oh! You're one of the Nobel-Prize-winners. In what field did you do your work?"
"In physics," I said.
"Oh. Well, nobody knows anything about that, so I guess we can't talk about it."
"On the contrary," I answered. "It's because somebody knows something about it that we can't talk about physics. It's the things that nobody knows anything about that we can discuss. We can talk about the weather; we can talk about social problems; we can talk about psychology; we can talk about international finance — gold transfers we can't talk about, because those are understood — so it's the subject that nobody knows anything about that we can all talk about!"
I don't know how they do it. There's a way of forming ice on the surface of the face, and she did it!"