Download The World According to Binmore

The World According to Binmore
Herbert Gintis
Department of Economics
University of Massachusetts
Amherst, Massachusetts, 01003
July 16, 1999
Ken Binmore, Game Theory and the Social Contract, is a two-volume
series published by MIT Press. I shall not discuss Volume I (Playing Fair,
1993). Indeed, Binmore urges economists to skip right to Volume II (Just
Playing, 1998), the subject of this review. Binmore writes as a political
philosopher in the tradition of David Hume and more recently, John Rawls
and John Harsanyi. His contribution to this tradition is highly original, and
will likely redirect research in this area for some time to come. I will focus
on three innovations in his work.
First, philosophers usually treat ethics as a system of rules that are
justified by the principles of reason. For Binmore, by contrast, ethics is
the scientific study of how humans behave and think. Binmore thus explores “the biological and social facts on which our moral intuitions are
based. . . Moral behavior in chimpanzees and baboons differs from behavior
in humans because their biological history differs from ours.” (511)
Binmore affirms the Rawls/Harsanyi ‘original position,’ according to
which just institutions are those that people would chose if they did not
know what positions they would hold in the society to which these institutions give rise. He rejects the standard Kantian justification for the original
position, however, in favor of a naturalistic one. The original position, he
holds, is “a stylized description of a fairness norm that has actually evolved
in human societies for sound biological reasons.” (viii)
Binmore reports extensively on contemporary ethnographies of huntergather societies, believing that such societies mirror the social and material
conditions the human race faced during its formative period as a species.
Such societies have no division of labor except for gender, and are politically egalitarian, decision-making power being quite equally distributed
among the adult males of the community. Binmore infers that fairness
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norms must be self-enforcing, and cannot depend on a hierarchical leader
(a “philosopher-king”) to enforce ethical principals. Moreover, since a division of labor (except for gender) is absent, deliberations in such groups
approximate the ‘original position.’
Binmore thus offers us a “coevolution of genes and culture” in which the
acceptance of original position moral arguments is written into our genes,
but the cultural content depends on local environmental conditions and
random variation. Again drawing on the ethnographic literature, Binmore
focuses on food sharing as the most important rule of justice to be decided
by a foraging group. In foraging societies, high variance foodstuffs such as
meat are equally shared, irrespective of who made the kill. Equal sharing is
thus a moral rule justified by reasoning from the original position of hunters
who do not know exactly which among them will be lucky or skilled.
Accepting original position moral arguments confers a fitness advantage
to human groups, and hence evolves genetically, because it allows a society “to single out one of the many equilibria typically available as Paretoimprovements on the status quo without the necessity for damaging and
potentially destabilizing internal conflict.” (209)
Binmore’s second innovation is to use evolutionary game theory to analyze social interactions. This adds a welcome degree of clarity to ethical
reasoning. Indeed, Binmore is quite clear that all of his substantive results
depend on the plausibility of the game theoretic models he presents and
analyzes. This relates to Binmore’s third innovation, which is to treat Just
Playing not as a stand-alone contribution to political philosophy, but as a
first step in a research program to which he expects many to contribute in
the coming years. This is in sharp contrast to classical political philosophy, in which works are treated as consummate, not to be tampered-with
statements. As an example of this stance, Binmore notes that many of
his conclusions may be overturned when his analysis is extended from twoperson to n-person games, and when we learn more about our evolutionary
history.
Binmore analyzes an indefinitely repeated game with two players (Adam
and Eve). In each period the players, knowing their position in society, play
a game G, called the ‘game of Life’ involving production, distribution, and
consumption. Prior to playing G, however, another ‘game of Morals’ M may
be played. Binmore describes this game as follows:
. . . the rules of the artificial game M require that Adam and
Eve pretend that each round of G is preceded by an episode
during which each player can call for the veil of ignorance to be
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lowered. They then bargain in the original position about which
equilibrium is to be operated when the veil is lifted. The rules of
M then require that the actions specified by this equilibrium be
implemented in future plays—unless Adam or Eve demand that
the veil of ignorance be lowered again for the agreement to be
renegotiated. An equilibrium of the natural game G is said to
be fair if its play would never give a player reason to appeal to
the device of the original position under the rules of the morality
game M . (11)
While the fairness norms that justify the rules of the games G and M
are biologically determined, the players in Binmore’s games are rational selfinterested agents. Thus all of the results of two-person game theory based
on the rational actor model can be deployed in analyzing social justice. It
follows in particular that “[i]n a well-ordered society, each citizen honors
the social contract because it is in his own self-interest to do so, provided
that enough of his fellow citizens do the same.” (5) There is no sense in
which moral behavior is opposed to self-interested behavior. Moreover, since
players do not behave ethically in bargaining, there is no sense in which the
institutions resulting from their bargaining have any abstract normative
standing. “Evolutionists simply seek to understand,” says Binmore, “why
some types of human organization survive better than others.. . . evolutionary
ethics offers no authority whatsoever to those who wish to claim that some
moral systems are somehow intrinsically superior to others.’ (179)
Different societies can thus embrace different institutions because comparisons in the original position depend on ‘empathetic preferences’ that are
culturally specific. It is in part for this reason that Binmore calls himself a
‘whig,’ by which he means a moderate progressive, not seduced by the grand
visions of a totally alternative society as proposed by the Left and the Right.
The latter two, he claims, make social judgments in a universal, ahistorical
manner that have nothing to do with the actual fairness processes in real
societies. Whigs like himself, he asserts “are content to aim at finding workable ways of making life just a little bit more bearable for everyone. . . My
pragmatic suggestion is that we adapt the fairness norms that are in daily
use for settling small-scale coordinating problems to large-scale problems of
social reform.” (258,500)
Since we live in a market society, Binmore’s whiggish sympathies and the
cultural specificity of judgments in the original position lead him to affirm
the justice of the market system. He says, “the market is precisely what one
should expect to see in the long run as a result of people’s personal prefer3
ences adapting over time to the use of the device of the original position as
a fairness norm.” (474) This homage to the market, however, is not a sign
of Binmore’s love for the system. “The market,’ he writes, is therefore the
final step in a process that first leaches out the moral content of a culture
and then erodes the autonomy of its citizens by shaping their personal preferences. . . a market cannot easily be corrupted because its institutions have
been corrupted already.” (475)
Just Playing is an important and welcome contribution to the literature.
The book does, however, have some faults. The most salient is that crucial
analytical material and discursive asides jumbled together. One must read
the whole book, and make numerous references back and forth, to understand the basic argument. Moreover, the book is intended for a general
audience interested in political philosophy, yet even professional economists
will find the analytical parts difficult to follow.
Another problem is that Binmore uses evolutionary game theory where
it suits him, but abandons it when it does not. For instance, the Nash equilibria he describes in the Game of Life depend on the folk theorem (p. 293),
while such equilibria in general are not stable with respect to plausible dynamic processes. Moreover the folk theorem depends on agents’ having long
time horizons, but Binmore gives no evolutionary reason why agents should
have long time horizons. Similarly, while Binmore uses naturalism to justify the assertion that Homo sapiens is genetically programed to accept the
original position, but he gives no empirical evidence that this is in fact the
case. Moreover, it is implausible that evolution imprinted us with an original position orientation, but in no other way affected our moral behavior,
so that the assumption of Homo economicus remains valid for bargaining
purposes. Laboratory experiments reveal forms of prosocial behavior (e.g.,
rejecting ‘unfair’ offers in an ultimatum game, or punishing free riders in a
public goods game) that relate directly to questions of justice and fairness,
yet contradict the Homo economicus model. The notion that human sociality can be explained by ‘enlightened self-interest,’ even when accompanied
by respect for the original position, will not likely survive a close study of
the evidence (Herbert Gintis, Game Theory Evolving, Princeton University
Press, 2000).
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