No More Learning

Sometimes he speaks of corn, at other times of labour,
as a standard measure; not the quantity of labour bestowed on the
production of any object, but the quantity which it can command in the
market: as if these were two equivalent expressions, and as if because a
man's labour had become doubly efficient, and he could therefore produce
twice the quantity of a commodity, he would necessarily receive twice
the former quantity in           for it.