value of a commodity can only be proportioned to its general power of purchasing so long as the commodities with which it is exchanged continue to be obtained with the same facility. But as it is known by experience that no considerable mass of commodities ever continues to be obtained with the same facility, it is observable that when we speak of the variations in the exchangeable value of a particular commodity, we refer almost invariably to its power of purchasing arising from intrinsic causes.
That this is so, is incontrovertibly proved by the manner in which we practically estimate the variations of value by money. In the same places, and for short periods, money is universally considered as a correct measure of value in the ordinary sense in which the term is used. If from any cause whatever the members of the society are willing and able to make a greater sacrifice in money, in order to obtain a particular commodity, we say that it has risen in value, without stopping to inquire into the state of other commodities. If corn be dear, on account of a deficient supply, we say that corn has risen in value; but if we still pay the same money for our coats, shirts, and shoes, we never think of saying that they have fallen in value, although on account of the rise in a great mass of raw produce, they will have diminished most essentially in their general power of purchasing. The corn is said to have risen in exchangeable value, because its power of purchasing has been affected by a cause intrinsic to the article itself, namely, a deficiency of its supply. The coats, shirts, and shoes, are said to have remained of the same value, because their supply, compared with the demand, appears to have remained the same, and nothing has operated to increase or diminish their power of purchasing arising from intrinsic causes. In neither case do we trouble ourselves about the extrinsic causes of their power of purchasing. During the short periods in which we consider the value of money as nearly constant, we invariably refer to the power of particular commodities to command, at different times, different quantities of
