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said, this is not really very interesting; we’re not going to sully our hands with this
stuff.
There is no justification for this in the game-theoretic sociology, just as there
was no justification for it in the mathematics sociology. Each one of these branches
of the discipline makes its contribution. In many ways, the coalitional theory has
done better than the strategic theory in giving insight into economic and other
environments. A prime example of this is the equivalence theorem, which gave
a game-theoretic foundation for the law of supply and demand. There has been
nothing of that generality or power in strategic game theory. Strategic game theory
has made important contributions to the analysis of auctions, but it has not given
that kind of insight into economics, or into any other discipline.
Another example of an important insight yielded by coalitional game theory
is the theory of matching markets. This whole branch of game theory—and it
is highly applied—grew out of the ’62 paper of Gale and Shapley “College Ad-
missions and the Stability of Marriage.” It is not quite as fundamental as the
equivalence theorem, but it is a very important application, certainly of compa-
rable importance to the work on auctions in strategic game theory, which is very
important. There is no reason to denigrate the contributions of coalitional game
theory, either on the applied or the theoretical level.
H: Indeed, Adam Brandenburger said that his students at Harvard Business
School found cooperative game theory much more relevant to them than the
noncooperative theory.
Let’s switch to another topic. You have had an enormous impact on the profes-
sion by influencing many people. I am talking first of all about your students. By
now you have had thirteen doctoral students. I think twelve of them are by now
professors, in Israel and abroad, who are well recognized in the field and also in
related fields.
A: Almost all the students eventually ended up in Israel, after a short break for
a postdoc or something similar abroad.
H: That’s not surprising since most of them—all except Wesley—started in
Israel and are Israelis.
A: There is quite a brain drain from Israel. A large proportion of prominent
Israeli scientists who are educated in Israel end up abroad—a much larger propor-
tion than among my students.
These are my doctoral students up until now: Bezalel Peleg, David Schmeidler,
Shmuel Zamir, Binyamin Shitovitz, Zvi Artstein, Elon Kohlberg, Sergiu Hart,
Eugene Wesley, Abraham Neyman, Yair Tauman, Dov Samet, Ehud Lehrer, and
Yossi Feinberg. Of these, three are currently abroad—Kohlberg, Wesley, and
Feinberg. Also, there are about thirty or forty masters students.
Each student is different. They are all great. In all cases I refused to do what
some people do, and that is to write a doctoral thesis for the student. The student
had to go and work it out by himself. In some cases I gave very difficult problems.
Sometimes I had to backtrack and suggest different problems, because the student
wasn’t making progress. There were one or two cases where a student didn’t make
INTERVIEW WITH ROBERT AUMANN
721
it—started working and didn’t make progress for a year or two and I saw that he
wasn’t going to be able to make it with me. I informed him and he left. I always
had a policy of taking only those students who seemed very, very good. I don’t
mean good morally, but capable as scientists and specifically as mathematicians.
All of my students came from mathematics. In most cases I knew them from my
classes. In some cases not, and then I looked carefully at their grades and accepted
only the very best. I usually worked quite closely with them, meeting once a week
or so at least, hearing about progress, making suggestions, asking questions. When
the final thesis was written I very often didn’t read it carefully. Maybe this is news
to Professor Hart, maybe it isn’t. But by that time I knew the contents of the work
because of the periodic meetings that we would have.
H: Besides, you don’t believe anything unless you can prove it to yourself.
A: I read very little mathematics—only when I need to know. Then, when
reading an article I say, well, how does one prove this? Usually I don’t succeed,
and then I look at the proof.
But it is really more interesting to hear from the students, so, Professor Hart,
what do you think?
H: Most doctoral students want to finish their thesis and get out as soon as
possible. Aumann’s students usually want to continue—up to a point, of course.
This was one of the best periods in my life—being immersed in research and
bouncing ideas back and forth with Professor Aumann; it was a very exciting
period. It was very educating for my whole life. Having a good doctoral advisor
is a great investment for life. There is a lot to say here, but it’s your interview, so
I am making it very short. There are many stories among your students, who are
still very close to one another.
F
IGURE
7. At the GAMES 1995 Conference in honor of Aumann’s sixty-fifth birthday,
Jerusalem, June 1995: Abraham Neyman, Bob Aumann, John Nash, Reinhard Selten, Ken
Arrow, Sergiu Hart (from left to right).
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SERGIU HART
Next, how about your collaborators? Shapley, Maschler, Kurz, and Dr`eze are
probably your major collaborators. Looking at your publications I see many other
coauthors—a total of twenty—but usually they are more focused on one specific
topic.
A: I certainly owe a lot to all those people. Collaborating with other people
is a lot of work. It makes things a lot more difficult, because each person has
his own angle on things and there are often disagreements on conceptual aspects.
It’s not like pure mathematics, where there is a theorem and a proof. There may
be disagreements about which theorem to include and which theorem not to
include, but there is no room for substantive disagreement in a pure mathematics
paper. Papers in game theory or in mathematical economics have large conceptual
components, on which there often is quite substantial disagreement between the
coauthors, which must be hammered out. I experienced this with all my coauthors.
You and I have written several joint papers, Sergiu. There wasn’t too much
disagreement about conceptual aspects there.
H: The first of our joint papers [50] was mostly mathematical, but over the
last one [82] there was some . . . perhaps not disagreement, but clarification of
the concepts. The other two papers [69, 70], together with Motty Perry, involved
a lot of discussion. I can also speak from experience, having collaborated with
other people, including some longstanding collaborations. Beyond mathematics,
the arguments are about identifying the right concept. This is a question of judg-
ment; one cannot prove that this is a good concept and that is not. One can
only have a feeling or an intuition that that may lead to something interesting,
that studying this may be interesting. Everybody brings his own intuitions and
ideas.
A: But there are also sometimes real substantive disagreements. There was a
paper with Maschler—“Some Thoughts on the Minimax Principle” [27]—where
we had diametrically opposed opinions on an important point that could not be
glossed over. In the end we wrote, “Some experts think A, others think ‘Not
A’.” That’s how we dealt with the disagreement. Often it doesn’t come to that
extreme, but there are substantial substantive disagreements with coauthors. Of
course these do not affect the major message of the paper. But in the discussion,
in the conceptualization, there are nuances over which there are disagreements.
All these discussions make writing a joint paper a much more onerous affair than
writing a paper alone. It becomes much more time-consuming.
H: But it is time well consumed; having to battle for your opinion and having
to find better and better arguments to convince your coauthor is also good for your
reader and is also good for really understanding and getting much deeper into
issues.
That is one reason why an interdisciplinary center is so good. When you
must explain your work to people who are outside your discipline, you cannot
take anything for granted. All the things that are somehow commonly known
and commonly accepted in your discipline suddenly become questionable. Then
you realize that in fact they shouldn’t be commonly accepted. That is a very
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