“All I had was my head and my books, and I thought a lot. I learned, because there was no interruption. I had access to myself, to my thinking.”

On life in hiding from Nazi authorities, p. 48
To Save a Life: Stories of Holocaust Rescue (2000)
Context: 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. I learned, because there was no interruption. I had access to myself, to my thinking. I wouldn't say that I particularly matured. The thinking was physics thinking. I was just short of twenty-two then.
I was in hiding for two years and two months, something like that. In all that time I went out very, very little, just once in a great while, after dark. 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.