Such a metal might then, by an unlimited division into parts exactly equal, be made to serve as a tolerable steady and universal measure. But the rivalship between the metals, and the perfect equality which is found between all their physical qualities, so far as regards purity, and divisibility, render them so equally well adapted to serve as the common measure of value, that they are universally admitted to pass current as money.
All measures ought to be invariable.
What is the consequence of this? That the one measures the value of the other, as well as that of every other thing. Now the moment any measure begins to be measured by another, whose proportion to it is not physically, perpetually, and invariably the same, all the usefulness of such a measure is lost. An example will make this plain.
A foot of measure is a determinate length. An English foot may be compared with the Paris foot, or with that of the Rhine; that is to say, it may be measured by them; and the proportion between their lengths may be expressed in numbers; which proportion will be the same perpetually. The measuring the one by the other will occasion no uncertainty; and we may speak of lengths by Paris feet, and be perfectly well understood by others who are used to measure by the English foot, or by the foot of the Rhine.
Consequences when they vary.
But suppose that a youth of twelve years old takes it into his head to measure from time to time, as he advances in age, by the length of his own foot, and that he divides this growing foot into inches and decimals: what can be learned from his account of measures? As he increases in years, his foot, inches, and subdivisions, will be gradually lengthening; and were every man to follow his example, and measure by his own foot, then the foot of a measure now established would totally cease to be of any utility.
This is just the case with the two metals. There is no determinate invariable proportion between their value; and the consequence of this is, that when they are both taken for measuring the value of other things, the things to be measured, like the lengths to be measured by the young man’s foot, without changing their relative proportion between themselves, change however with respect to the denominations of both their measures. An example will make this plain.
Let us suppose an ox to be worth three thousand pounds weight of wheat, and the one and the other to be worth an ounce of gold, and the ounce of gold to be worth exactly fifteen ounces of silver: If the case should happen, that the proportional value between gold and silver should come to be as 14 is to 1, would not the ox, and consequently the wheat, be estimated at less in silver, and more in gold, than formerly? I ask farther, if it would be in the power of any state to prevent this variation in the measure of the value of oxen and wheat, without putting into the unit of their money less silver and more gold than formerly.
Defects of a silver standard.
If therefore any particular state should fix the standard of the unit of their money to one species of the metals, while in fact both the one and the other are actually employed in measuring value; does not such a state resemble the young man, who measures all by his growing foot. For, if silver, for example, be retained as the standard, while it is gaining upon gold one fifteenth additional value; and if gold continues all the while to determine the value of things as well as silver, it is plain that, to all intents and purposes, this silver measure is lengthening daily, like the young man’s foot, since the same weight of it must become every day equivalent to more and more of the same commodity; notwithstanding that we suppose the same proportion to subsist, without the least variation, between that commodity and every other species of things alienable.