"I don't feel frightened by not knowing things, by being lost in a mysterious universe without any purpose, which is the way it really is, as far as I can tell, possibly. It doesn't frighten me."

"Scientific knowledge is a body of statements of varying degrees of certainty—some most unsure, some nearly sure, but none absolutely certain."

"You know, the dumbest goddamn student you ever saw can understand things if you explain them right. So if you can’t explain it, it’s because you don’t understand it."

"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…"

"Mathematics is not a science, but a language. It's a tool for science."