Front Page Titles (by Subject) Chapter III: The Functions of Money - Money and the Mechanism of Exchange
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Chapter III: The Functions of Money - William Stanley Jevons, Money and the Mechanism of Exchange 
Money and the Mechanism of Exchange (New York: D. Appleton and Co. 1876).
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The Functions of Money
We have seen that three inconveniences attach to the practice of simple barter, namely, the improbability, of coincidence between persons wanting and persons possessing; the complexity of exchanges, which are not made in terms of one single substance; and the need of some means of dividing and distributing valuable articles. Money remedies these inconveniences, and thereby performs two distinct functions of high importance, acting as—
In its first form money is simply any commodity esteemed by all persons, any article of food, clothing, or ornament which any person will readily receive, and which, therefore, every person desires to have by him in greater or less quantity, in order that he may have the means of procuring necessaries of life at any time. Although many commodities may be capable of performing this function of a medium more or less perfectly, some one article will usually be selected, as money par excellence, by custom or the force of circumstances. This article will then begin to be used as a measure of value. Being accustomed to exchange things frequently for sums of money, people learn the value of other articles in terms of money, so that all exchanges will most readily be calculated and adjusted by comparison of the money values of the things exchanged.
A Standard of Value.
A third function of money soon develops itself. Commerce cannot advance far before people begin to borrow and lend, and debts of various origin are contracted. It is in some cases usual, indeed, to restore the very same article which was borrowed, and in almost every case it would be possible to pay back in the same kind of commodity. If corn be borrowed, corn might be paid back, with interest in corn; but the lender will often not wish to have things returned to him at an uncertain time, when he does not much need them, or when their value is unusually low. A borrower, too, may need several different kinds of articles, which he is not likely to obtain from one person; hence arises the convenience of borrowing and lending in one generally recognized commodity, of which the value varies little. Every person making a contract by which he will receive something at a future day, will prefer to secure the receipt of a commodity likely to be as valuable then as now. This commodity will usually be the current money, and it will thus come to perform the function of a standard of value. We must not suppose that the substance serving as a standard of value is really invariable in value, but merely that it is chosen as that measure by which the value of future payments is to be regulated. Bearing in mind that value is only the ratio of quantities exchanged, it is certain that no substance permanently bears exactly the same value relatively to another commodity; but it will, of course, be desirable to select as the standard of value that which appears likely to continue to exchange for many other commodities in nearly unchanged ratios.
A Store of Value.
It is worthy of inquiry whether money does not also serve a fourth distinct purpose—that of embodying value in a convenient form for conveyance to distant places. Money, when acting as a medium of exchange, circulates backwards and forwards near the same spot, and may sometimes return to the same hands again and again. It subdivides and distributes property, and lubricates the action of exchange. But at times a person needs to condense his property into the smallest compass, so that he may hoard it away for a time, or carry it with him on a long journey, or transmit it to a friend in a distant country. Something which is very valuable, although of little bulk and weight, and which will be recognised as very valuable in every part of the world, is necessary for this purpose. The current money of a country is perhaps more likely to fulfil these conditions than anything else, although diamonds and other precious stones, and articles of exceptional beauty and rarity, might occasionally be employed.
The use of esteemed articles as a store or medium for conveying value may in some cases precede their employment as currency. Mr. Gladstone states that in the Homeric poems gold is mentioned as being hoarded and treasured up, and as being occasionally used in the payment of services, before it became the common measure of value, oxen being then used for the latter purpose. Historically speaking, such a generally esteemed substance as gold seems to have served, firstly, as a commodity valuable for ornamental purposes; secondly, as stored wealth; thirdly, as a medium of exchange; and, lastly, as a measure of value.
Separation of Functions.
It is in the highest degree important that the reader should discriminate carefully and constantly between the four functions which money fulfils, at least in modern societies. We are so accustomed to use the one same substance in all the four different ways, that they tend to become confused together in thought. We come to regard as almost necessary that union of functions which is, at the most, a matter of convenience, and may not always be desirable. We might certainly employ one substance as a medium of exchange, a second as a measure of value, a third as a standard of value, and a fourth as a store of value. In buying and selling we might transfer portions of gold; in expressing and calculating prices we might speak in terms of silver; when we wanted to make long leases we might define the rent in terms of wheat, and when we wished to carry our riches away we might condense it into the form of precious stones. This use of different commodities for each of the functions of money has in fact been partially carried out. In Queen Elizabeth's reign silver was the common measure of value; gold was employed in large payments in quantities depending upon its current value in silver, while corn was required by the Act 18th Elizabeth, c. VI. (1576), to be the standard of value in drawing the leases of certain college lands.
There is evident convenience in selecting, if possible, one single substance which can serve all the functions of money. It will save trouble if we can pay in the same money in which the prices of things are calculated. As few people have the time or patience to investigate closely the history of prices, they will probably assume that the money in which they make all minor and temporary bargains, is also the best standard in which to register debts and contracts extending over many years. A great mass of payments too are invariably fixed by law, such as tolls, fees, and tariffs of charges: many other payments are fixed by custom. Accordingly, even if the medium of exchange varied considerably in value, people would go on making their payments in terms of it, as if there had been no variation, some gaining at the expense of others.
One of our chief tasks in this book will be to consider the various materials which have been employed as money, or have been, or may be, suggested for the purpose. It must be our endeavour, if possible, to discover some substance which will in the highest degree combine the characters requisite for all the different functions of money, but we must bear in mind that a partition of these functions amongst different substances is practicable. We will first proceed to a brief review of the very various ways in which the need of currency has been supplied from the earliest ages, and we will afterwards analyse the physical qualities and circumstances which render the substances employed more or less suited to the purpose to which they were applied. We may thus arrive at some decision as to the exact nature of the commodity which is best adapted to meet our needs in the present day.