Scientific knowledge is an enabling power to do either good or bad — but it does not carry instructions on how to use it.

Outside of their particular area of expertise scientists are just as dumb as the next person.

When it came time for me to give my talk on the subject, I started off by drawing an outline of the cat and began to name the various muscles. The other students in the class interrupt me: "We *know* all that!" "Oh," I say, "you *do*? Then no *wonder* I can catch up with you so fast after you've had four years of biology." They had wasted all their time memorizing stuff like that, when it could be looked up in fifteen minutes.

To test whether you have learned an idea or a definition, rephrase what you just learned without using the new word.

I am not interested in what today's mathematicians find interesting.

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.

The present situation in physics is as if we know chess, but we don't know one or two rules.