articles on economic affairs; and he suggested to me that in future I would do well to explain why models are sometimes useful and why they usually are not At the time I was fairly flabbergasted to question the usefulness of economic models at this late date seemed rather strange. But the economist's idea that economic theory for the most part consists of models has by no means been accepted by intellectuals outside our field. In fact, if one looks at the favorite economic writers of the non-economist intellectual--Robert Reich, Lester Thurow, John Kenneth Galbraith--one realizes that they have in common an aversion to or ignorance of modeling There are model-oriented economists. like alan blinder who also write for a broader audience and they don't put their equations in their books and articles; but the skeleton of the models that structur their thought is visible under the surface to those who know how to look. By contrast, in the writings of Reich or Galbraith what you read is what you get- there is no hidden mathematical structure to the argument, no diagram one might draw on a blackboard or simulation one might run on a computer to clarify the point In this the situation in economics is virtually identical to that in evolutionary theory. Ask a working biologist who is the greatest living evolutionary thinker, and he or she will probably answer John Maynard Smith(with nods to George Williams and william Hamilton). Maynard Smith not only has a name that should have made him an economist; he writes and thinks like an economist, representing evolutionary issues with stylized mathematical models that are sometimes confronted with data sometimes simulated on the computer, but always serve as the true structure informing the verbal argument. A textbook like his Evolutionary Genetics(1989) feels remarkably comfortable for an academic economist: the style is familiar, and even a good bit of the content looks like things economists do too. But ask intellectuals in general for a great evolutionary thinker and they will surely name Stephen Jay Gould-- who receives one brief, dismissive reference in Maynard Smith (1989).(One of my ill-advised moves in the conversation with the editor was to point out that the index to Tyson(1993) contains no references either to Reich or to Thurow) What does Gould have that Maynard Smith does not? He is a more accessible writer--but evolutionary theory is, to a far greater extent than economics, blessed with excellent popularizers writers like Dawkins(1989)or Ridley (1993), who provide beautifully written expositions of what researchers have learned ( Writers like Gould or Reich are not, in the proper sense, popularizers:a popularizer reports on the work of a community of scholars, whereas these writers argue for their own, heterodox points of view). No, what makes Gould so popular with intellectuals is not merely the quality of his writing but the fact that, unlike Dawkins or ridley, he is not trying to explain the essentially mathematical logic of modern evolutionary theory. It's not just that there are no equations or simulations in his books he doesn't even think in terms of the mathematical models that inform the work of writers like Dawkins. That is what makes his work so appealing. The problem, of course, that evolutionary theory -the real thing -is based on mathematical models; indeed, increasingly it is based on computer simulation And so the very aversion to mathematics that makes gould so appealing to his audience means that his books, while they may seem to his readers to contain deep ideas, seem to people who actually know the field to be mere literary confections with little serior intellectual content, and much of that simply wrong. In particular, readers whose ideas of evolution are formed by reading Gould's work get no sense of the power and reach of the theory of natural selection--if anything, they come away with a sense that modern thought has shown that theory to be inadequate Economics is not as well served by its writers as evolution. Still, the distinctive feature of the writersarticles on economic affairs; and he suggested to me that in future I would do well to explain why models are sometimes useful and why they usually are not. At the time I was fairly flabbergasted: to question the usefulness of economic models at this late date seemed rather strange. But the economist's idea that economic theory for the most part consists of models has by no means been accepted by intellectuals outside our field. In fact, if one looks at the favorite economic writers of the non-economist intellectual -- Robert Reich, Lester Thurow, John Kenneth Galbraith -- one realizes that they have in common an aversion to or ignorance of modeling. There are model-oriented economists, like Alan Blinder, who also write for a broader audience, and they don't put their equations in their books and articles; but the skeleton of the models that structure their thought is visible under the surface to those who know how to look. By contrast, in the writings of Reich or Galbraith what you read is what you get -- there is no hidden mathematical structure to the argument, no diagram one might draw on a blackboard or simulation one might run on a computer to clarify the point. In this the situation in economics is virtually identical to that in evolutionary theory. Ask a working biologist who is the greatest living evolutionary thinker, and he or she will probably answer John Maynard Smith (with nods to George Williams and William Hamilton). Maynard Smith not only has a name that should have made him an economist; he writes and thinks like an economist, representing evolutionary issues with stylized mathematical models that are sometimes confronted with data, sometimes simulated on the computer, but always serve as the true structure informing the verbal argument. A textbook like his Evolutionary Genetics (1989) feels remarkably comfortable for an academic economist: the style is familiar, and even a good bit of the content looks like things economists do too. But ask intellectuals in general for a great evolutionary thinker and they will surely name Stephen Jay Gould -- who receives one brief, dismissive reference in Maynard Smith (1989). (One of my ill-advised moves in the conversation with the editor was to point out that the index to Tyson (1993) contains no references either to Reich or to Thurow). What does Gould have that Maynard Smith does not? He is a more accessible writer -- but evolutionary theory is, to a far greater extent than economics, blessed with excellent popularizers: writers like Dawkins (1989) or Ridley (1993), who provide beautifully written expositions of what researchers have learned. (Writers like Gould or Reich are not, in the proper sense, popularizers: a popularizer reports on the work of a community of scholars, whereas these writers argue for their own, heterodox points of view). No, what makes Gould so popular with intellectuals is not merely the quality of his writing but the fact that, unlike Dawkins or Ridley, he is not trying to explain the essentially mathematical logic of modern evolutionary theory. It's not just that there are no equations or simulations in his books; he doesn't even think in terms of the mathematical models that inform the work of writers like Dawkins. That is what makes his work so appealing. The problem, of course, is that evolutionary theory -- the real thing -- is based on mathematical models; indeed, increasingly it is based on computer simulation. And so the very aversion to mathematics that makes Gould so appealing to his audience means that his books, while they may seem to his readers to contain deep ideas, seem to people who actually know the field to be mere literary confections with little serious intellectual content, and much of that simply wrong. In particular, readers whose ideas of evolution are formed by reading Gould's work get no sense of the power and reach of the theory of natural selection -- if anything, they come away with a sense that modern thought has shown that theory to be inadequate. Economics is not as well served by its writers as evolution. Still, the distinctive feature of the writers