I spent every night until four in the morning on my dissertation, until I came to the point when I could not write another word, not even the next letter. I went to bed. Eight o'clock the next morning I was up writing again.

Some years ago John Kenneth Galbraith wrote in an essay on his efforts at writing a history of economics: 'As one approaches the present, one is filled with a sense of hopelessness; in a year and possibly even a month, there is now more economic comment in the supposedly serious literature than survives from the whole of the thousand years commonly denominated as the Middle Ages ... anyone who claims to be familiar with it all is a confessing liar.' I believe that all physicists would subscribe to the same sentiments regarding their own professional literature. I do at any rate.

[Heisenberg's seminal 1925 paper initiating quantum mechanics marked] one of the great jumps—perhaps the greatest—in the development of twentieth century physics.

Once I even took the train to Utrecht, forty miles from Amsterdam, with my yellow star, this star which I still have. Why did I go? I just wanted to visit some friends. I was a little bit crazy, a little bit insane.

To make a discovery is not necessarily the same as to understand a discovery. Not only Planck but also other physicists were intially at a loss as to what the proper context of the new postulate really was.

One of the things I learned, one of the strangest things, is how to think. There was nothing else to do. I couldn't see people, or go for a walk in the forest. All I had was my head and my books, and I thought a lot.

The rule of the game was never assume that anybody, however honorable, would be able to stand up under torture. If Mr. X, who knew where I was, was caught for some reason, I should move.