Possibility of the Impossibility of Economics--论文代写范文精选

这导致的问题是，什么是标准的,一个简单的答案是,抽象模型只是对模型的定义,然后从这些定义中,这短暂的想法,最终必须被定义适当的对象的应用。下面的essay代写范文进行详述。

Abstract
Let us suppose that economic theory does consist of abstract models, in the sense indicated at the end of the previous section. In what way might such models be true or useful? It will be helpful here to consider a distinction discussed by Nancy Cartwright (1990, ch. 5), between abstraction and idealization. In an idealized model, causal variables are not ignored, but rather set to convenient values. Since important variables are all included, it is supposed that idealized models are approximately true. Abstract models, on the other hand, describe only the effects of selected causal influences. The point emphasized in the preceding section, that economic models are not expected to be even approximately true, and Hausman's idea that even the ceteris paribus laws in economics are vague as to what exactly has to be equal, make it clear that economic laws must be abstract rather than idealized. This leads us to the question, What are the criteria of, if not truth, then rightness or legitimacy, for such abstract models?

A simple answer would be that abstract models say merely that if there were objects subject to only the forces defined in the model, then from the definition of those forces it follows that the objects would behave in the ways specified by the model. This has momentary appeal in view of the idea that forces must ultimately be defined in terms of the kind of response they produce in appropriate objects to which they are applied. But this reply is plainly too easy to help with our question. On this criterion, any model is legitimate if it is coherent. It cannot, therefore, address the issue of which models have some relevance to the real world. It is tempting, then, to resort to counterfactual claims about real objects. Thus, for example, we might interpret models of consumer behavior as asserting that if people were motivated solely by self-interest, had perfect information, complete transitive preferences, etc., they would . . . To which a natural response would be, Why should we care about the hypothetical behavior of people so different from ourselves?

This entire discussion raises important philosophical difficulties that I shall, however, note only to pass over. It is questionable whether self-interest, for example, can coherently be thought of as one force competing with others in the manner of the combining or opposing forces of classical mechanics. (Though perhaps with self-interest in the guise of greed such a vision is implicit in certain, generally religious, models of moral deliberation.) However, assuming for present purposes that some adequate psychological theory can be provided to make sense of the economic model, let me consider further the proposed counterfactual. The response to the objection at the end of the last paragraph must be, presumably, that these people are not different from ourselves with regard to their dispositional structure. The claim is about how we would behave subject to only the forces specified. And this is not merely to serve as a definition of those forces (unless it is to be subject to the objection of triviality), but to say something contingent about our causal or dispositional structure. But even if we pass over all the notorious general difficulties with the interpretation of counterfactuals, it is still extremely doubtful whether such counterfactual claims have any relevance to real people in the real world.

We should begin with the fairly obvious point that the forces central to economic models, notably self-interest, must at least be seen as important determinants of human behavior. It is unimaginable, for example, that anyone should be much interested in a theory of some social phenomenon that treated human behavior soley insofar as it derived from embarrassment, or pique. With this assumption in mind, the question also arises, under what circumstances is self-interest a crucial or even decisive determinant of human behavior. Is this a universal feature of human nature, or something true only in a fairly specific set of social contexts9? Apparently training in economics has some tendency to elicit the kind of behavior assumed in economic models10, which suggests that such behavior might be very sensitive to details of the social environment. McCloskey (1990, p.140) makes some scathing remarks about the prevalence of unrestrained self-interest among his fellow-economists11. Regardless of the answer to this question, even assuming that self-interest is a sufficiently crucial determining factor of human behavior to justify the development of models of its consequences, what does the counterfactual tell us about human behavior in contexts in which other important factors are also acting such as altruism, force of habit, deference to local custom, systematic "irrationality" of the kind increasingly familiar to psychologists12, etc.

I suggest that if there is any sense to be made of the question what is the causal force of self-interest abstracted from such other factors relevant to the determination of economic behavior, it can only be because it is possible, at least in principle, to combine the causal influences of all such forces so as to produce a resultant that fully determines the relevant behavior. It is not merely that without such a possibility the abstract model can have no practical significance, but rather that this is a condition of the intelligibility of the abstract model. One way to make this point is to note that abstraction is often thought of as involving the subtraction of causal factors other than those under consideration (see Cartwright 1990, p. 197). But this metaphor only makes sense if there is some totality (the resultant of the various factors) from which this subtraction can begin, and if this really is a sum of the various causal factors involved.

I see no reason why these conditions should be met. The assumption that there must be some such resultant of the causal influences on social, or specifically economic, phenomena is an expression of the commitment to determinism, or at least the probabilistic successors to determinism that still insist on the existence of the complete causal truth about any sequence of events. I cannot address the difficulties with these views in any detail here13. However, in the absence of a metaphysical argument for the necessity of determinism, the general failure to provide empirically adequate models of social phenomena is, ipso facto, a failure to provide evidence for the truth of determinism. Evidence for determinism, I suggest, is hard to come by.

It may be easier to see what is at stake here in the context of a concrete example. I do not at all mean to deny that there are economic causes. So, for instance, a reduction in the price of a commodity will generally cause an increase in demand for that commodity unless some other causal factor counteracts that causal tendency. Does this mean that there is some objectively real relation between price and demand of the sort expressed in a demand curve? Not necessarily. What an objectively real demand curve appears to add to the mere recognition of the causal capacity of the reduction in price, is the expectation that the relation between price and quantity demanded should be quantitatively stable14. Thus it implies that if, on two different occasions, the price falls from P1 to P2, the quantity demanded should, on both occasions, rise from Q1 to Q2. Of course, this is not really what anyone expects. Tastes may have changed, substitutes or complements become more or less available, etc. So, as usual, this implication will be qualified as true only ceteris paribus. This, in turn, implies that if the change in demand on the second occasion is not the same as on the first, there must be some explanation of this fact--some other factor must not have been equal. But only a commitment to determinism makes it seem necessary that there be such an explanation. I see no reason why demand curves should not evolve in erratic and unpredictable ways over history so that quantitative relations between price and quantity would have very little inductive value for predicting the future. In short, the failure of economics to predict future phenomena might reflect not merely the inability of economists to take account of the numerous factors impinging on economic reality, but rather the inherent unpredictability of the phenomena concerned. And if this were the case, finally, it would be impossible even to make sense of the counterfactuals that were supposed to underwrite the abstract economic models.

There are two kinds of response to the recognition of this possibility short of abandoning entirely the traditional quantitative methodology of economics, empirical optimism and metaphysics. By the latter, I mean that we might offer a metaphysical argument that there must be stable economic relations regardless of our inability to discover them. I have argued at length against this kind of metaphysical prejudice elsewhere (1993), and shall not discuss it further here. (Somewhat relatedly, we might suppose in the way suggested by the quote from Friedman at the beginning of this paper, that the assumption of the existence of underIying order is a precondition of scientific research. I shall explain below why I think that even in a merely methodological sense, such a presupposition is unacceptable.) In accordance with the former strategy, we may certainly continue to hope that empirical evidence will eventually sustain the stability of quantitative economic relations, though I suggest that this amounts to litttle more than blind faith. No doubt it may in the end turn out that, perhaps with the incorporation of specific further factors and barring gross and identifiable interventions, economic self-interest really does come close to providing an empirically adequate explanation or prediction of economic phenomena. But given the ease with which significant interfering factors can be imagined, this seems something of a forlorn hope.

It will be recalled that in offering evolutionary biology as an area of science the legitimacy of which does not seem seriously threatened by lack of predictive potential, I mentioned that the absence of serious alternatives to the theory of evolution as an explanation of the origin and diversity of life was important to its credibility. Could the same be said of economics? Surely not. As I have indicated, it seems hard to deny that the forces assumed by economic theory act, for example, on the prices of and demand for commodities. So any plausible account of the determination of these parameters will have to leave room for these causal influences. But how large a part of the story these forces will provide is another matter. In the short run, demand and supply may seldom be in equilibrium even if eventually producers will react to increasing inventories or shortages. These responses may seldom keep pace with endogenously determined changes in demand. Perhaps prices are largely determined by rule of thumb pricing techniques (cost + X%, for example), imitation, or guesswork, and demand fluctuates continuously with changes in fashion, advertising strategies, and so on. And most importantly unless determinism is assumed, there need be no stable and consistent way in which these various forces combine.

An even more significant employment of the parallel between economics is the following. The TINA15 defence of evolutionary theory is persuasive when it is deployed on behalf of broad qualitative accounts of aspects of the history of life. It is much less plausible if it is taken to legitimate detailed mathematical models of particular evolutionary phenomena. Indeed I have argued elsewhere (1993, ch.6) that population genetics, supposedly a source of detailed mathematical models of evolutionary changes in the genetic constitution of populations of organisms, is an extremely dubious enterprise. Similarly, insofar as economics restricts itself to identifying causal influences on economic phenomena, and deploying these in narrative accounts of economic phenomena, it should be seen as constituting a generally salutary contribution to general historiography. But the mismatch between the apparent precision and scope of theoretical economic models, and any reasonable assessment of the importance of the processes they describe to real economic history, makes most of economic theory an unpromising candidate for epistemologically respectable science. （essay代写)

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