There is no learning without having to pose a question. And a question requires doubt.

There are theoretical physicists who imagine, deduce, and guess at new laws, but do not experiment; and then there are experimental physicists who experiment, imagine, deduce, and guess.

But there is nothing in biology yet found that indicates the inevitability of death.

You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts.

Study hard what interests you the most in the most undisciplined, irreverent and original manner possible.

Science alone of all the subjects contains within itself the lesson of the danger of belief in the infallibility of the greatest teachers of the preceding generation.

The game I play is a very interesting one. It's imagination in a straightjacket, which is this: that it has to agree with the known laws of physics. ... It requires imagination to think of what's possible, and then it requires an analysis back, checking to see whether it fits, whether its allowed, according to what's known, okay?