AT DIFFERENT PERIODS. 9]
surd; but I lie under a great mistake, if it is
not really the proposition which X Y Z* has
been attacking, while he supposed himself to
be in logical combat with the first.

It is difficult to imagine how an error of this
kind (if I am right in supposing it to be one)
should have escaped a mind evidently well
versed in the detection of ambiguities in argu-
mentation. It appears to have arisen, as in the
case of Mr. Ricardo, from blending the compa-
rison of contemporary commodities with that
of the same commodity at different periods,
which led them to the erroneous inference, that
because the valueof A at one period did not bear
the same relation to the value of its producing
labour as at another period, therefore the values
of two contemporary commodities did not bear
the same relation to each other as the values of
the labour respectively bestowed on their pro-
duction.

* X Y Z is the designation assumed by the Author of the
Dialogues.