A MEASURE AND A CAUSE OF VALUE. 177

truly objects) © be ascertained without considerable
 difficulty :’ in most cases, indeed, it
could not be ascertained at all. A measure of
value, however, which cannot be practically
applied, is worthless*.”
It was probably some obscure and undefined
impression of this truth, which, when Mr. Ricardo
 deliberately set himself to treat on the
subject of a measure of value, influenced him
to speak, not of labour itself in that capacity,
but of a commodity produced by an invariable
quantity of labour. If the quantity of producing
 labour really determines the value of
commodities, it seems on a first view useless to
require for a measure an object of which the
producing labour is invariable, when we may
have recourse to the labour itself. But Mr. Ricardo
 probably perceived, that a knowledge of
the quantity of producing labour in objects
would be in most cases difficult of attainment,
and therefore betook himself to the considera~

x

London Magazine for May, 1824, page 559.