Richard Feynman: Doing (page 3)

“…In that same period there was Newton, there was Harvey studying the circulation of the blood, there were people with methods of analysis by which progress was being made! You can take every one of Spinoza's propositions and take the contrary propositions and look at the world--and you can't tell which is right. Sure, people were awed because he had the courage to take on these great questions, but it doesn't do any good to have the courage if you can't get anywhere with the question…”

Richard Feynman book The Pleasure of Finding Things Out

From Omni interview, "The Smartest Man in the World" (1979) or from the book p. 195.
The Pleasure of Finding Things Out (1999)

People , World , Courage , Question

“What I cannot create, I do not understand.Know how to solve every problem that has been solved.”

Richard Feynman

on his blackboard at the time of death in February 1988; from a photo in the Caltech archives http://archives.caltech.edu/pictures/1.10-29.jpg

Problem

“Of course if we make good things, it is not only to the credit of science; it is also to the credit of the moral choice which led us to good work. Scientific knowledge is an enabling power to do either good or bad — but it does not carry instructions on how to use it. Such power has evident value — even though the power may be negated by what one does with it.I learned a way of expressing this common human problem on a trip to Honolulu. In a Buddhist temple there, the man in charge explained a little bit about the Buddhist religion for tourists, and then ended his talk by telling them he had something to say to them that they would never forget — and I have never forgotten it. It was a proverb of the Buddhist religion:To every man is given the key to the gates of heaven; the same key opens the gates of hell.What then, is the value of the key to heaven? It is true that if we lack clear instructions that enable us to determine which is the gate to heaven and which the gate to hell, the key may be a dangerous object to use.But the key obviously has value: how can we enter heaven without it?”

Richard Feynman

The Value of Science (1955)

Hell , Religion , Forgetting , Bad luck

“Do not keep saying to yourself, if you can possibly avoid it, "But how can it be like that?"”

Richard Feynman book The Character of Physical Law

because you will get "down the drain", into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.
Concerning the apparent absurdities of quantum behavior.
Source: The Character of Physical Law (1965), chapter 6, “Probability and Uncertainty — the Quantum Mechanical View of Nature,” p. 129

“What do we mean by “understanding” something? We can imagine that this complicated array of moving things which constitutes “the world” is something like a great chess game being played by the gods, and we are observers of the game. We do not know what the rules of the game are; all we are allowed to do is to watch the playing. Of course, if we watch long enough, we may eventually catch on to a few of the rules. The rules of the game are what we mean by fundamental physics.”

Richard Feynman

Even if we knew every rule, however, we might not be able to understand why a particular move is made in the game, merely because it is too complicated and our minds are limited. If you play chess you must know that it is easy to learn all the rules, and yet it is often very hard to select the best move or to understand why a player moves as he does. So it is in nature, only much more so.
volume I; lecture 2, "Basic Physics"; section 2-1, "Introduction"; p. 2-1
The Feynman Lectures on Physics (1964)

God , Imagination , Understanding , Game