In the 1940's and 1950's proponents of a genuinely scientific political science looked with admiration on social sciences that were then more advanced, like sociology and psychology. As these behavioralists gained intellectual ground, historically and philosophically minded critics complained about mindless quantification, the reduction of political man and woman to the product of childhood socialization, and about a research agenda that focused on academic questions about political psychology and political sociology instead of improving people and government.

In the 1970's scholars dissatisfied with the prevailing nonrational conception of politics looked to disciplines like operations research and economics for models that would help to restore volition to a central place in political science. The establishment behavioralists along with surviving historically and philosophically minded critics now complained about mindless mathematization, the reduction of political man and woman to atomistic calculators, and the capture of the research agenda by applied mathematicians and "economic imperialists."

Peter DaSilva for The New York Times
Morris P. Fiorina, a professor of political science at Stanford.

Most recently, scholars concerned that biology has been overlooked are trying to move biopolitics -- which looks at how genetic and physiological tendencies are related to political behavior -- to a more prominent place on the discipline's shelf of approaches. If they succeed, they too will hear the complaints of the proponents of other previously borrowed approaches. As this brief review suggests, political science is defined more by its subject matter -- political institutions, processes and behavior -- than by any specific methodology. Other social sciences have characteristic ways of thinking. Economics, for example, has been called the study of how people make choices, while sociology has been called the study of how people have no choices to make. In contrast, political science has no characteristic approach. Historically it has tried out quite a few with differing degrees of success. But since success is relative and at least partly subjective, arguments naturally occur.

The central premise of the approaches known as rational choice, economic and public choice (although these variants differ in important particulars) is that behavior is purposive. Political behavior is not solely the product of psychological drives, socialization or organizational norms. Rather, individuals have goals they try to achieve, acting as rationally as their knowledge, resources and the situation permit. Here are two illustrations.

First, much Congressional scholarship of the 1950's and 1960's treated members of Congress as acting primarily in response to norms and role expectations enforced by other members. Rational choice scholars in the 1970's suggested that a better starting point would be the presumption that first and foremost, members of Congress wanted to be re-elected and acted accordingly. That assumption would not describe all members all the time, of course, but it would fit more members more of the time than any other assumption, and thus was the most appropriate starting point.

Second, by the mid-1960's studies of presidential voting behavior had concluded that the most important determinant of vote choice was party identification, viewed as a psychological allegiance that was largely apolitical, almost like an antibody you got from your family at an early age. By the late 1960's, as demonstrations raged outside, as a third party candidate -- George Wallace -- contended for the presidency and as long-time Democratic identifiers deserted their party, it became increasingly difficult to stand in front of a class and say that people voted on the basis of immutable and apolitical party identifications, paying little attention to issues. In the 1970's and 1980's rational choice scholars refocused attention on the importance of issues and government performance and re-examined party identification, finding a political component within it.

Most people would find it hard to argue with examples like these. Why then is rational choice at all controversial within political science?

One reason is that practitioners sometimes claim too much, a common fault among enthusiastic adherents of any approach. Bringing the volitional element back in should not mean kicking the nonrational and emotional out. In my own teaching I always emphasize that rational choice arguments are more useful where the stakes are relatively high and the number of players relatively low. Making a reasoned decision is not worth the effort if the consequences are trivial or if your decision makes no difference to the outcome or both.

Thus, rational choice arguments should be more appropriate for the study of why 100 senators vote as they do on a Supreme Court nomination than for the study of why nine million people vote as they do for California Secretary of State (or why the nine million vote at all for that matter).

That is not to say that a social-psychological approach has nothing to say about senators engaged in high politics, nor that a rational choice approach has nothing to say about ordinary citizens engaged in mass politics, but the two approaches should differ in their applicability to these situations.

Others dislike the rational choice approach because it is unapologetically social scientific. Certainly not everyone who works under the rational choice rubric constructs mathematical models, but many do; and formalization and generalization are ideals of social science. Those who prize detailed narratives of particular cases understandably feel devalued by rational choice.

Similarly, those who believe that a country's unique history or culture determines the operation of its institutions and political processes may reject the rational choice approach. In both these cases I believe that the critics' complaints often are less directed at a particular approach than at the idea of social science in general.

On the other hand, even some card-carrying social scientists view the rational choice approach with skepticism. Rational choice is more self-consciously theoretical than other research programs. Practitioners engage in model-building, and they make simplifying assumptions and draw logical consequences using the classic deductive method. Understandably, scholars whose approaches are inductive and empirical sometimes feel that rational choice models omit much of the rich detail they have painstakingly compiled. Readers will recognize this as yet another appearance of the fox versus hedgehog debate.

All in all, criticisms of the flowering rational choice research program are not completely without merit, but neither are they debilitating. Given the heterogeneity of the political science profession, it would be surprising if any one approach won general acceptance.

The best rational choice applications carry over central features of the earlier institutional and behavioral traditions. And I am confident that even as tomorrow's students borrow new intellectual frameworks (biopolitics?), they will carry over central features of rational choice.

onsider this: The last 40 years have seen an enormous infusion of the methodologies of economics into the academic study of politics, but the practitioners would be hard pressed to tell you what has been learned as a result.

	George Ruhe for The New York Times
	Ian Shapiro, chairman of Yale's political science department.

Political science journals abound in rational choice models that are shrouded in jargon and largely impenetrable to the uninitiated. Yet all this technification didn't help political scientists offer wisdom to constitutional designers after the collapse of Communism. Nor have they said anything important about more conventional politics that was not previously known.

Typically rational choice theorists either ignore or recycle conventional wisdom through their models or they specify the models so vaguely as to render them compatible with every possible outcome. Often this vagueness is obscured by intimidating mathematics, creating a misleading appearance of rigor.

When rational choice models are specified in ways that make clear, arresting predictions, they often lead to results that are contradicted by what we know about politics. For example, they imply that egoistic rational maximizers have no reason to vote, given the infinitesimal odds of affecting the result. Yet people vote in the millions all over the world. Sometimes they are willing to die for the right to vote. Indeed, people invest time and resources in all kinds of collective political activities, demonstrations and campaigns even though this is irrational from the standpoint of strategic rationality. No matter how much you care about the result, in all but a handful of cases it would make more sense to "free ride" -- let others contribute while you reap the benefits.

Defenders of rational choice respond with endless adaptations of the meaning of rationality, saving the models at the price of rendering them banal. Thus voters are said to be maximizing their sense of civic virtue. Alternatively, people are said to take part in collective action in response to "selective incentives" or bribes offered by organizers. To get a sense of how illuminating this is, ask yourself how likely it is that would-be political demonstrators choose between rallies for and against nuclear power plants, racial profiling or abortion clinics on the basis of which side offers better cookies and refreshments.

Another common tack is to adapt complex models from game theory -- a field that tries to analyze human interactions from the gains and losses observed in games -- to explain the behavior of politicians. But these models take no account of the reality that some politicians are more strategically able than others and that political outcomes may just as often be due to ideology, luck or blunder as to the net consequence of well-informed strategic calculations by all the relevant players. Small wonder that game-theoretic models cannot tell you who will win the primaries or the elections (or even why the winners won after the fact), why negotiated transitions to democracy succeed in some circumstances and fail in others or why countries do or do not go to war.

Practitioners sometimes respond that rational choice explanations are "other things equal" explanations. The difficulty is that all too often most of the explanation lurks in that clause. Other things equal, tall people are more likely than short people to bump their heads on the moon. How does it help us to know that?

Why has the rational choice approach become so influential in political science when it illuminates so little about politics? The answer lies in the professional imperatives political scientists face. Too many of them buy into the misguided idea that the only way to develop a science of politics (as distinct from journalistic commentary) is to have a universal deductive theory, and they then turn to economics in search of it. (The economists turned to physics for the same reason; I leave it to others to debate the wisdom of that move.)

The result is a theory in search of applications, exemplifying the old adage that when the only tool you have is a hammer, everything around you starts to look like a nail. In fact the things political scientists study differ so much from one another that it is highly unlikely that any "one size fits all" theory will do the job. In addition to nails, there are screws, bolts, wheels, pulleys, pipes and cables out there, and a host of other objects for which it is as yet unclear which is the best tool to use or, indeed, what the objects themselves actually are.

Rather than engage in method-driven political science, it makes more sense to start with a problem: why do politicians who lose elections sometimes attempt coups rather than accept the popular verdict? Why do democracies seem better able to prevent famines than nondemocracies? What leads some people to vote for ethnic parties rather than those that appeal to economic interest or some other ideology, and why does this vary from time to time and place to place?

Once the question is stated, the search should begin for the most viable explanation. This choice should be influenced by a host of things: the accumulated stock of knowledge about the question and closely related ones, what appears to have worked in the study of comparable questions, and the hunches of the researcher.

The goal should be to get the right answer, not to vindicate a pet approach. The most promising way to advance toward it is to develop empirical generalizations that can be tested by the predictions they make, modified when they fail, and tested again and again and again. Perhaps this inductive approach will add up to a general theory of politics one day, perhaps not. In the interim, it is more likely to illuminate political arrangements and behavior than the endless elaboration of models that purport to explain everything and as a result explain nothing.

This is not to mention an additional danger: if the next several cohorts of graduate students are trained primarily in the techniques of rational choice rather than in substantive political subjects, the rational choice movement may actually erode the stock of knowledge about politics that is passed on to subsequent generations.