The Theory of Money and Credit - Ludwig von Mises [13]
Particular attention has been devoted, especially in recent times, to the function of money as a general medium of payment. Indirect exchange divides a single transaction into two separate parts which are connected merely by the ultimate intention of the exchangers to acquire consumption goods. Sale and purchase thus apparently become independent of each other Furthermore, if the two parties to a sale-and-purchase transaction perform their respective parts of the bargain at different times, that of the seller preceding that of the buyer (purchase on credit), then the settlement of the bargain, or the fulfillment of the seller's part of it (which need not be the same thing), has no obvious connection with the fulfillment of the buyer's part. The same is true of all other credit transactions, especially of the most important sort of credit transaction—lending. The apparent lack of a connection between the two parts of the single transaction has been taken as a reason for regarding them as independent proceedings, for speaking of the payment as an independent legal act, and consequently for attributing to money the function of being a common medium of payment. This is obviously incorrect. "If the function of money as an object which facilitates dealings in commodities and capital is kept in mind, a function that includes the payment of money prices and repayment of loans...there remains neither necessity nor justification for further discussion of a special employment, or even function of money, as a medium of payment." [9]
The root of this error (as of many other errors in economics) must be sought in the uncritical acceptance of juristical conceptions and habits of thought. From the point of view of the law, outstanding debt is a subject which can and must be considered in isolation and entirely (or at least to some extent) without reference to the origin of the obligation to pay. Of course, in law as well as in economics, money is only the common medium of exchange. But the principal, although not exclusive, motive of the law for concerning itself with money is the problem of payment. When it seeks to answer the question, What is money? it is in order to determine how monetary liabilities can be discharged. For the jurist, money is a medium of payment. The economist, to whom the problem of money presents a different aspect, may not adopt this point of view if he does not wish at the very outset to prejudice his prospects of contributing to the advancement of economic theory.
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[1] See Wicksell, Über Wert, Kapital und Rente (Jena, 1893; London, 1933), pp. 50 f.
[2] The conclusion that indirect exchange is necessary in the majority of cases is extremely obvious. As we should expect, it is among the earliest discoveries of economics. We find it clearly expressed in the famous fragment of the Pandects of Paulus: "Quia non semper nec