Before I go any further I would like to say a few words about some people I have known and particularly appreciated. I have met many great men in my life. I mentioned Von Neumann with whom I did my post-doc and I could mention many others. But two I would like to mention are not known in the same way, in particular Marcel-Paul Schätzenberger. When I was writing my Ph.D. in 1952, which I defended in 1952, about a year before, I met a man in Paris at the Henri Poincaré Institute. After a seminar he - I was very impressed by his seminar - we went to have a beer together and then went to have dinner together, then we had a chat together, and then about 5 am the next day we left each other, and we saw each other again the next day, then a month later and so on. He died two years ago. For this long period we had, perhaps one could say, a single conversation going on and interrupted sometimes for a day, sometimes for a month, sometimes for many years. Why did Schätzenberger like me? Why did I like him? Well, there are many reasons one cannot understand, but one reason linked us very strongly- that he too could not make up his mind about who he was and what field he was in. He happened to have studied medicine and got a medical degree during the war, but also studied mathematics and got in due time a Ph.D. in mathematics and studied many things. In his idle time he was studying Hungarian because why study an easy language if there are hard ones? But almost always when I had started working on some exotic field that nobody cared for, I was sure that Marco, as we all called him, would find fun and make some ferocious comments about how terrible and marvellous and awful and wonderful it was. He was my worst critic, more precisely my most critical critic, and my best friend. The difference between his work and mine is that his work remained, how should I say, scattered over many fields. He continued to do this field, that other field, without even attempting to draw a link between his various activities. After he died I realised that he had had many passions, which he never shared with me because he thought I would not be interested; that is, I knew only one side, or five sides, of the many other sides of this man. I, to the contrary, always wanted my different interests to come together because I always felt them to be one aspect of the same story.
