An inveterate fallacy asserted that things and services exchanged are of equal value. Value was considered as objective, as an intrinsic quality inherent in things and not merely as the expression of various people’s eagerness to acquire them. People, it was assumed, first established the magnitude of value proper to goods and services by an act of measurement and then proceeded to barter them against quantities of goods and services of the same amount of value. This fallacy frustrated Aristotle’s approach to economic problems and, for almost two thousand years, the reasoning of all those for whom Aristotle’s opinions were authoritative. It seriously vitiated the marvelous achievements of the classical economists and rendered the writings of their epigones, especially those of Marx and the Marxian school, entirely futile. The basis of modern economics is the congition that is precisely the disparity in the value attached to the objects exchanged that results in their being exchanged. People buy and sell only because they appraise the things given up less than those received. Thus the notion of a measurement of value is vain. An act of exchange neither preceded nor accompanied by any process which could be called a measuring of value. An individual may attach the same value to two things; but then no exchange can result. But if there is a diversity in valuation, all that can be asserted with regard to it is that one a is valued higher, that it is preferred to one b. Values and valuations are intensive quantities and not extensive quantities. They are not susceptible to mental grasp by the application of cardinal numbers.
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There is no method available to construct a unit of value. Let us remember that two units of a homogeneous supply are necessarily valued differently. The value attached to the nth unit is lower than that attached to the (n – 1)th unit.
In the market society there are money prices. Economic calculation is calculation in terms of money prices. The various quantities of goods and services enter into this calculation with the amount of money for which they are bought and sold on the market or for which they could prospectively be bought and sold. It is a fictitious assumption that an isolated self-sufficient individual or the general manager of a socialist system, i.e., a system in which there is no market for means of production, could calculate. There is no way which could lead one from the money computation of a market economy to any kind of computation in a nonmarket system.
Human Action, P. 205f