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

“Ingels: A number of current theoretical explorations will turn out to be passing fancies...”

“The first thing Bohr said to me was that it would only then be profitable to work with him if I understood that he was a dilettante. The only way I knew to react to this unexpected statement was with a polite smile of disbelief. But evidently Bohr was serious. He explained how he had to approach every new question from a starting point of total ignorance. It is perhaps better to say that Bohr's strength lay in his formidable intuition and insight rather than erudition.”

“One of the absolute rules I learned in the war was, don't know anything you don't need to know, because if you ever get caught they will get it out of you.”

“Progress leads to confusion leads to progress and on and on without respite. Every one of the many major advances … created sooner or later, more often sooner, new problems. These confusions, never twice the same, are not to be deplored. Rather, those who participate experience them as a privilege.”

“I made a discovery, perhaps known to others but new to me: I need not put myself center stage but can rather place myself at the side, like a Greek chorus. As the curtain rises, I can walk to the center and can speak as follows: I wish to tell you of happenings in the twentieth century, as I witnessed them and reflected upon them. You will see me return to center stage, but only occasionally. Once that imagery had gotten hold of me, I went back to Ida and said yes, I shall try.”

“On the day we were caught, Lion and I had been talking about writing a memorandum on the fate of the Jewish war children living in hiding or among Dutch families … we were the representatives of the Zionist youth organization. … Lion who had been taking notes of the discussion, put these papers in his jacket pocket when he took a break from lunch. When the Germans caught us they discovered his notes. If those papers had been in my pocket I would have never lived to be seventy. I have led a strange life, a set of complete coincidences.”