Book I: Chapter 5 - Page 2

labour, which it enables him to purchase or command. The exchangeable value
of every thing must always be precisely equal to the extent of this power
which it conveys to its owner.

But though labour be the real measure of the exchangeable value of all
commodities, it is not that by which their value is commonly estimated. It
is often difficult to ascertain the proportion between two different
quantities of labour. The time spent in two different sorts of work will not
always alone determine this proportion. The different degrees of hardship
endured, and of ingenuity exercised, must likewise be taken into account.
There may be more labour in an hour's hard work, than in two hours easy
business ; or in an hour's application to a trade which it cost ten years
labour to learn, than in a month's industry, at an ordinary 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 for any other commodity. The butcher seldom carries his beef or his
mutton to the baker or the brewer, in order to exchange them for bread or
for beer ; but he carries them to the market, where he exchanges them for
money, and afterwards exchanges that money for bread and for beer. The
quantity of money which he gets for them regulates, too, the quantity of
bread and beer which he can afterwards purchase. It is more natural and
obvious to him, therefore, to estimate their value by the quantity of money,
the commodity for which he immediately exchanges them, than by that of
bread and beer, the commodities for which he can exchange them only by the
intervention of another commodity ; and rather to say that his