and obvious employment. But it is not easy to find any accurate measure either of hardship or ingenuity. In exchanging, indeed, the different productions of different sorts of labour for one another, some allowance is commonly made for both. It is adjusted, however, not by any accurate measure, but by the higgling and bargaining of the market, according to that sort of rough equality which, though not exact, is sufficient for carrying on the business of common life.
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 produce. 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