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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 1 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 2 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). 4