I first got to meet Professor Chern as a student in 1962, in an AMS Summer Institute in Santa Barbara. Contrary to all the stories you have heard in the last two days, he did not take me out to lunch that day. I came to Berkeley as an Assistant Professor in 1965, and for the next thirty-five years I saw him often. It may be that I saw him even more after he really retired from the department and MSRI around 1985.
Our canonical image of Professor Chern is someone with impeccable judgment, so I’d like to share three stories with you about the few occasions when he was wrong. The first took place in 1949, between his departure from China and his arrival in Chicago. It may be recalled that he proved the Gauss–Bonnet theorem in late 1943, and finished his manuscript on Chern classes in July, 1945, in China. Soon after that he was called upon to create the Institute of Mathematics in China. For the next three years he had to be the all-in-one teacher, caretaker, and administrator of the institute, and these duties consumed him. He was then between 35 and 38 years old, and for a mathematician, these are the peak years of creativity. But he willingly sacrificed those years for the good of Chinese mathematics. Such onerous responsibilities took their toll, however, and he paid the price in his own mathematical work. Although he tried to keep his research going, it was not humanly possible under the circumstance to sustain the same high level as in the earlier years. Eventually, errors crept into his papers. So it came to pass that when he arrived at the Institute for Advanced Study in early 1949, he thought his career as a research mathematician was over; he did not believe he was capable of doing creative work anymore. Such self-doubt is in stark contrast with our usual perception of him as someone with unlimited self-confidence about mathematics. It makes him more human.
Of course he was wrong; he was completely wrong this time. The rest, as they say, is history.
A second story takes us to the early 1980s, when China was beginning to open up to the West after the long hibernation during the Cultural Revolution of 1966 to 1976. Professor Chern, in concert with the Chinese government, invited many mathematicians to visit China, including Atiyah, Bott, and many others. He did all this with a definite goal in mind, and I got a glimpse of it when he expressed frustration that the young mathematician in China did not make good use of the opportunity to talk to these distinguished guests and learn from them. We know how much he learned by talking to , and we also know that his conversations with Weil in 1943 made him aware of the Gauss–Bonnet enigma at the time. His own experiences no doubt colored his thinking, and that was why he was frustrated: why couldn’t they all be like me? This is the case of a great general not being in tune with the obstacles faced by his foot soldiers. I think he was wrong to expect so much from the young mathematicians of China because it takes confidence and talent to benefit from talking to a distinguished colleague. For example, it is amusing to contemplate how a young person, intellectually not quite the equal of Professor Chern himself, could benefit from talking to a curmudgeon like ., , , , ,
The last story is not about mathematics at all but about Chinese politics. After his visit to China in 1972 (right in the middle of the Cultural Revolution) Professor Chern began to tell those around him that Madame Mao would try to seize supreme power. He probably got some vibes to this effect during his visit, but it was news to many of us. Then toward the end of Mao’s life in 1976, he predicted that she would succeed. I want to assure you that he did not want her to succeed, but he had to call it like it is. He was not someone who would allow sentimentality to cloud his judgment. The topologistwas horrified by that prospect and he made a bet with Professor Chern that she would fail. At stake was a fancy dinner. I was witness to the bet so I would get my dinner either way, but I must say that, in all the years when I almost always agreed with Professor Chern in and out of mathematics, that time I was rooting against him like crazy. As we all know, Professor Chern lost the bet and everybody was happy at the end.
I would add a few comments about the Chern persona. Many people have referred to his charm and grace, but to my mind, those words do not begin to tell the story. His charisma had to be felt firsthand to be fully understood. I think Raoul Bott captured its essence by not using any standard words or phrases to describe what he saw. In 1979, there was a symposium at Berkeley in honor of Professor Chern’s retirement. On that occasion, Bott began his lecture like this:
It is a great pleasure to address this symposium in honor of my dear friend, teacher, and collaborator. I first met Chern in 1950, when he dropped in to visit Princeton for just one day and I sat near him at lunch. I don’t suppose that you remember this occasion, my dear friend, though I am sure I contrived to attract your attention by some impertinence or other. For I was immediately captivated by what you said and how you said it.
We are here this evening to honor Professor Chern’s memory, seven years after he passed away. You just might be curious, as one of my colleagues is, as to why he is singled out among many distinguished mathematicians for such adulation. There is no lack of first rate mathematicians of today that can inspire awe and admiration with their intellectual prowess, but awe and admiration do not directly translate into adulation. It may be that Hirzebruch got to the heart of the matter when in 2001, in the preface to a volume of Results in Mathematics dedicated to Professor Chern, he said:
There have been many meetings and volumes dedicated to Chern, always as a symbol of affection and gratitude.
Notice that Hirzebruch did not even mention Chern class. Rather, he spoke of affection for Professor Chern. Now to win over our minds there is a simple algorithm: prove great theorems. But to win over our hearts, there is no algorithm known to man. Perhaps we can gain an appreciation of how Professor Chern succeeded in doing that by reflecting on something he once said. In describing his experiences withand , perhaps the two most important mentors of his life, he said they were both extremely modest and personable. But the difference to Professor Chern was that whereas with Cartan, one could talk to him as a friend for hours without being aware that he was a great mathematician, with , one would know not only that he was a great mathematician but also that he knew he was great. Then he added that he preferred Cartan’s way. It would seem that Professor Chern managed to learn not only moving frames from Cartan, but this personal secret as well. He made us feel that he was one of us, and we surrendered our hearts to him without knowing.
On this occasion, I would like to close by remembering Mrs. Chern, because as Professor Chern wrote so movingly in the preface to his Selecta:
I would not conclude this account without mentioning my wife’s role in my life and work. Through war and peace and through bad and good times we have shared a life for forty years, which is both simple and rich. If there is credit for my mathematical works, it will be hers as well as mine.