Every commodity, besides, is more frequently exchanged for, and thereby compared with, other commodities than with labour. It is more natural, therefore, to estimate its exchangeable value by the quantity of some other commodity than by that of the labour which it can purchase. The greater part of people, too, understand better what is meant by a quantity of a particular commodity than by a quantity of labour. The one is a plain palpable object; the other an abstract notion, which, though it can be made sufficiently intelligible, is not altogether so natural and obvious.

But when barter ceases, and money has become the common instrument of commerce, every particular commodity is more frequently exchanged for money than for any other commodity. The butcher seldom carries his beef or his mutton to the baker, or the brewer,