INTERVIEW WITH ROBERT AUMANN
725
That sort of sums it up. Correlated equilibrium had a big impact. The work on
repeated games, the equivalence principle, the continuum of players, interactive
epistemology–all had a big impact.
Citations do give a good general idea of impact. But one should also look
at the larger picture. Sometimes there is a body of work that all in all has a
big impact, more than the individual citations show. In addition to the above-
mentioned topics, there is incomplete information, NTU-values and NTU-games
in general—with their many applications—perfect and imperfect competition,
utilities and subjective probabilities, the mathematics of set-valued functions and
measurability, extensive games, and others. Of course, these are not disjoint; there
are many interconnections and areas of overlap.
There is a joint paper with Jacques Dr`eze [51] on which we worked very, very
hard, for very, very long. For seven years we worked on it. It contains some of the
deepest work I have ever done. It is hardly cited. This is a paper I love. It is nice
work, but it hasn’t had much of an impact.
H: Sometimes working very hard has two bad side effects. One is that you have
solved the problem and there is nothing more to say. Two, it is so hard that nobody
can follow it; it’s too hard for people to get into.
We were talking about various stations in your life. Besides City College, MIT,
Princeton, and Hebrew University you have spent a significant amount of time
over the years at other places: Yale, Stanford, CORE, and lately Stony Brook.
A: Perhaps the most significant of all those places is Stanford and, specifi-
cally, the IMSSS, the Institute for Mathematical Studies in the Social Sciences—
Economics. This was run by Mordecai Kurz for twenty magnificent years between
1971 and 1990. The main activity of the IMSSS was the summer gatherings, which
lasted for six to eight weeks. They brought together the best minds in economic
theory. A lot of beautiful economic theory was created at the IMSSS. The meetings
were relaxed, originally only on Tuesdays and Thursdays, with the whole morning
devoted to one speaker; one or two speakers in the afternoon, not more. A little
later, Wednesday mornings also became part of the official program. All the rest
of the time was devoted to informal interaction between the participants. Kenneth
Arrow was a fixture there. So was Frank Hahn. Of course, Mordecai. I came every
year during that period.
It was an amazing place. Mordecai ran a very tight ship. One year he even
posted guards at the doors of the seminar room to keep uninvited people out. But
he himself realized that that was going a little far, so that lasted only that one
summer.
Another anecdote from that period is this: the year after Arrow got the Nobel
Prize, he was vacationing in Hawaii at the beginning of July, and did not turn up
for the first session of the summer. Mordecai tracked him down, phoned him and
said, Kenneth, what do you think you are doing? You are supposed to be here;
get on the next plane and come down, or there will be trouble. The audacity of
the request is sufficiently astounding, but even more so is that Arrow did it. He
cancelled the rest of his vacation and came down and took his seat in the seminar.
726
SERGIU HART
The IMSSS was tremendously influential in the creation of economic theory
over those two decades. And it was also very influential in my own career. Some of
my best work was done during those two decades—much of it with very important
input from the summer seminar at the IMSSS. Also, during those two decades I
spent two full sabbaticals at Stanford, in ’75–’76 and in ’80–’81. This was a very
important part of my life. My children used to say that California is their second
home. Being there every summer for twenty years, and two winters as well, really
enabled me to enjoy California to the fullest. Later on, in the nineties, we were
again at Stanford for a few weeks in the summer. I told my wife there was a friend
whom I hadn’t seen in a year. She said, who, and I said, the Sierra Nevada, the
mountains. We had been there a few weeks and we hadn’t gone to the mountains
yet. We went, and it was a beautiful day, as always. Many times during those
years we would get up at 3 or 4 in the morning, drive to eastern California, to
the beautiful Sierra mountains, spend the whole day there from 7 or 8
A
.
M
. until
9
P
.
M
., and then drive back and get to Palo Alto at 1
A
.
M
.; exhausted, but deeply
satisfied. We climbed, hiked, swam, skied.
The Sierra Nevada is really magnificent. I have traveled around the whole
world, and never found a place like it, especially for its lakes. There are grander
mountains, but the profusion and variety of mountain lakes in the Sierra is unbe-
lievable. I just thought I would put that in, although it has nothing to do with game
theory.
H: Getting back to the IMSSS summers: besides those who came every year,
there were always a few dozen people, from the very young who were in the ad-
vanced stages of their doctoral studies, to very senior, established economists.
People would present their work. There would be very exciting discussions.
Another thing: every summer there were one or two one-day workshops, which
were extremely well organized, usually by the very senior people like you; for
example, you organized a workshop on repeated games in 1978 [42]. One would
collect material, particularly material that was not available in print. One would
prepare notes. They were duplicated and distributed to everybody there. They
served for years afterwards as a basis for research in the area. I still have notes
from those workshops; they were highly influential.
In all the presentations, you couldn’t just come and talk. You had to prepare
meticulously, and distribute the papers and the references. The work was serious
and intensive, and it was very exciting, because all the time new things were
happening. It was a great place.
A: You are certainly right—I forgot to mention all the other people who were
there, and who varied from year to year. Sometimes people came for two or
three or four consecutive years. Sometimes people came and then didn’t come the
next summer and then came again the following summer. But there was always a
considerable group of people there who were contributing, aside from the three or
four “fixtures.”
Another point is the intensity of the discussion. The discussion was very free-
wheeling, very open, often very, very aggressive. I remember one morning I was