[76 DIFFERENCE BETWEEN

It is certainly true, that, provided quantity of
labour were the sole cause of value, we should
always be able to deduce the value of two comimodities
 from a knowledge of the quantities of
labour which they respectively required to produce
 them ; and in this sense, quantity of labour
 would be at once the cause and the measure
 of value. But even under these circumstances,
 an author would not be justified in an
indiscriminate use of the terms; nor could he
fall into such an error, had he a distinct apprehension
 of the difference between the two
ideas.

[t would by no means follow, however, from
quantity of labour being the cause of value,
that it would be of any service as a measure.
On this point we may adopt the language of
the author of the Dialogues: ‘ If it had been
proposed as a measure of value, we might
justly demand that it should be ready and easy
of application ; but it is manifestly not so; for
the quantity of labour employed in producing
A, ¢ could not in many cases’ (as Mr. Malthus