I have to keep going to find out ultimately what is the matter with it in the end. - Richard Feynman

Well, we're getting a little philosophical and serious, ok? Let's go back to what we're doing. One day we look at a map and this capital is K-Y-Z-Y-L and we decided it would be fun to go there because it's so obscure and peculiar. It's a game. It's not serious. It doesn't involve some deep philosophical point of view about authority or anything. It's just the fun of having an adventure to try to go to a land that we'd never heard of, that we knew was an independent country once, no longer an independent country, find out what it's like. And discover as we went along that nobody went there for a long time and it's isolated made it more interesting. But, you know, many explorers liked to go to places that are unusual. And, it's only for the fun of it. I don't go for this philosophical interpretation of "our deeper understanding of what we’re doing." We haven't any deep understanding of what we're doing. If we tried to understand what we're doing, we'd go nutty.

...Dirac discovered the correct laws for relativity quantum mechanics simply by guessing the equation. The method of guessing the equation seems to be a pretty effective way of guessing new laws. This shows again that mathematics is a deep way of expressing nature, and any attempt to express nature in philosophical principles, or in seat-of-the-pants mechanical feelings, is not an efficient way.
...It always bothers me that, according to the laws as we understand them today, it takes a computing machine an infinite number of logical operations to figure out what goes on in no matter how tiny a region of space, and no matter how tiny a region of time. How can all that be going on in that tiny space? Why should it take an infinite amount of logic to figure out what one tiny piece of space/time is going to do? So I have often made the hypotheses that ultimately physics will not require a mathematical statement, that in the end the machinery will be revealed, and the laws will turn out to be simple, like the chequer board with all its apparent complexities.

The scientist has a lot of experience with ignorance and doubt and uncertainty, and this experience is of very great importance, I think. When a scientist doesn't know the answer to a problem, he is ignorant. When he has a hunch as to what the result is, he is uncertain. And when he is pretty darn sure of what the result is going to be, he is still in some doubt. We have found it of paramount importance that in order to progress we must recognize our ignorance and leave room for doubt. Scientific knowledge is a body of statements of varying degrees of certainty — some most unsure, some nearly sure, but none absolutely certain.<P> Now, we scientists are used to this, and we take it for granted that it is perfectly consistent to be unsure, that it is possible to live and not know. But I don't know whether everyone realizes this is true. 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 question — to doubt — to not be sure. I think that it is important that we do not forget this struggle and thus perhaps lose what we have gained.