AT DIFFERENT PERIODS. 79

*“ The value of a commodity,” says he, ““ or
the quantity of any other commodity for which
it will exchange, depends on the relative quantity
 of labour which is necessary for its production,
 and not on the greater or less compensation
 which is paid for that labour.”
In the first part of this sentence he appears
to be speaking of contemporary commodities,
but in the latter clause he has changed his
ground : it does not form a proper logical counterpart
 to the former: there is, I think, an implied
 although an unconscious reference to the
same commodity at different periods. For if
not, if he is speaking in the latter clause also
of contemporary commodities, the amount of
the proposition would be this :—
“ The values of two contemporary commodities,
 A and B, are to each other as the quantities
 of labour necessary to their production,
and they are not to each other as the values of
the labour employed in their production.”
But if commodities are to each other as the
quantities, they must also be to each other as the