He begins by insisting on the fact that labour in the modern world is
divided with such a general and such an increasing minuteness that each
labour produces one kind of product only, of which he himself can
consume but a small fraction, and often consumes nothing. His own
product, therefore, has for him the character of wealth only because he
is able to exchange it for commodities of other kinds; and the amount of
wealth represented by it depends upon what the quantity of other
assorted commodities, which he can get in exchange for it, is. What,
then, is the common measure, in accordance with which, as a fact, one
kind of commodity will exchange for any other, or any others? For his
answer to this question Marx goes to the orthodox economists of his
time--the recognised exponents of the system against which his own
arguments were directed--and notably, among these, to Ricardo; and,
adopting Ricardo's conclusions, as though they were axiomatic, he
asserts that the measure of exchange between one class of commodities
and another--such, for example, as cigars, printed books, and
chronometers--is the amount of manual labour, estimated in terms of
time, which is on an average necessary to the production of each of
them. His meaning in this respect is illustrated with pictorial
vividness by his teaching with regard to the form in which the measure
of exchange should embody itself. This, he said, ought not to be gold or
silver, but "labour-certificates," which would indicate that whoever
possessed them had laboured for so many hours in producing no matter
what, and which would purchase anything else, or any quantity of
anything else, representing an equal expenditure of labour of any other
kind.

Having thus settled, as it seemed to him beyond dispute, that manual
labour, estimated in terms of time, is the sole source and measure of
economic values or of wealth, Marx goes on to point out that, by the