35. Every species of merchandize does not present a scale
equally commodious. It is proper to prefer the use of such as are
not susceptible of any great alteration in quality, and have a
value principally relative to the number and quantity.
But although all merchandize has essentially this property of
representing any other, is able to serve as a common measure, to
express its value, and to become a universal pledge to procure
any of them by way of exchange, yet all cannot be employed with
the same degree of facility for these two uses. The more
susceptible any merchandize is to change its value by an
alteration in its quality, the more difficult it is to make it a
scale of reference for the value of others. For example, if
eighteen pints of wine of Anjou are equivalent in value to a
sheep, eighteen pints of Cape wine may be equivalent to eighteen
sheep. Thus he who to express the value of a sheep, would say it
is worth eighteen pints of wine, would employ an equivocal
language, and would not communicate any precise idea, at least
until he added some explanation, which would be very
inconvenient. We are, therefore, obliged to choose for a scale of
comparison, such commodities as being more commonly in use, and
consequently of a value more generally known, are more like each
other, and of which consequently the value has more relation to
the quantity than the quality.
