When World War II came along, which was when I was a teenager, we all expected we would have anthrax bombs and this kind of stuff. We thought it would be a biological war. Fortunately it wasn't and, but it's because the danger is still there and by some miracle we escaped all that, so you never can tell what it going to happen, but biology certainly could be even worse than physics and chemistry.

New directions in science are launched by new tools much more often than by new concepts. The effect of a concept-driven revolution is to explain old things in new ways. The effect of a tool-driven revolution is to discover new things that have to be explained.

Mind and intelligence are woven into the fabric of our universe in a way that altogether surpasses our understanding.

One of the memorable moments of my life was when Willard Libby came to Princeton with a little jar full of crystals of barium xenate. A stable compound, looking like common salt, but much heavier. This was the magic of chemistry, to see xenon trapped into a crystal.

[On Richard P. Feynman's live demonstration of the rigidity of the O-rings when cold that doomed the space shuttle Challenger, killing seven astronauts:] The public saw with their own eyes how science is done, how a great scientist thinks with his hands, how nature gives a clear answer when a scientist asks her a clear question.

It is characteristic of all deep human problems that they are not to be approached without some humor and some bewilderment.

It is not surprising that honest and well-informed experts can disagree about facts. But beyond the disagreement about facts, there is another deeper disagreement about values.