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Milton Friedman's book ''Essays in Positive Economics'' (1953) is a collection of earlier articles by the author with as its lead an original essay "The Methodology of Positive Economics," on which this article focuses. ==The Methodology of Positive Economics== The most basic counsel of this essay is to respect John Neville Keynes's distinction between ''positive'' and ''normative'' economics, what ''is'' vs. what ''ought to be'' in economic matters.〔A more general distinction was made by David Hume in his discussion of the is-ought problem.〕 The essay sets out an epistemological program for Friedman's own research. The essay argues that economics as ''science'' should be free of normative judgments for it to be respected as objective and to inform normative economics (for example whether to raise the minimum wage). Normative judgments frequently involve implicit ''predictions'' about the consequences of different policies. The essay suggests that such differences in principle could be narrowed by progress in positive economics (1953, p. 5). The essay argues that a useful economic theory should ''not'' be judged primarily by its tautological completeness, however important in providing a consistent system for classifying elements of the theory and validly deriving implications therefrom. Rather a theory (or hypothesis) must be judged by its: * ''simplicity'' in being able to predict at least as much as an alternate theory, although requiring less information〔Simplicity in Friedman's sense may be described as an application of ''Occam's razor''. The essay refers to Occam's razor in a different context (Friedman, 1953, pp. 12-13n).〕 * ''fruitfulness'' in the precision and scope of its predictions and in its ability to generate additional research lines (p. 10). In a famous and controversial passage, Friedman writes that: :Truly important and significant hypotheses will be found to have "assumptions" that are wildly inaccurate descriptive representations of reality, and, in general, the more significant the theory, the more unrealistic the assumptions (in this sense) (p. 14). Why? Because such hypotheses and descriptions extract only those crucial elements sufficient to yield relatively precise, valid predictions, omitting a welter of predictively irrelevant details. Of course descriptive unrealism by itself does not ensure a "significant theory" (pp. 14–15). From such Friedman rejects testing a theory by the realism of its assumptions. Rather simplicity and fruitfulness incline toward such assumptions and postulates as utility maximization, profit maximization, and ideal types—not merely to ''describe'' (which may be beside the point) but to ''predict'' economic behavior and to provide an engine of analysis (pp. 30–35). On profit maximization, for example, firms are posited to push each line of action to the point of equating the relevant marginal revenue and marginal cost. Yet, answers of businessmen to questions about the factors affecting their decisions may show no such calculation. Still, if firms act ''as if'' they are trying to maximize profits, that is the relevant test of the associated hypothesis (pp. 15, 22, 31). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Essays in Positive Economics」の詳細全文を読む スポンサード リンク
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