_X_. The great law which governs exchangeable value has now been stated and argued. Next, it seems, we must ask, what are its uses? This is a question which you or I should not be likely to ask; for with what color of propriety could a doubt be raised about the use of any truth in any science? still less, about the use of a leading truth? least of all, about the use of _the_ leading truth? Nevertheless, such a doubt _has_ been raised by Mr. Malthus. _Phæd_. On what ground or pretence. _X_. Under a strange misconception of Mr. Ricardo's meaning. Mr. Malthus has written a great deal, as you may have heard, against Mr. Ricardo's principle of value; his purpose is to prove that it is a false principle; independently of which, he contends that, even if it were a true principle, it would be of little use. [Footnote: _Vide_ the foot-note to p. 54 of "The Measure of Value."] _Phæd_. Little use? In relation to what? _X_. Ay, _there_ lies the inexplicable mistake: of little use as a _measure_ of value. Now, this is a mistake for which there can be no sort of apology; for it supposes Mr. Ricardo to have brought forward his principle of value as a standard or measure of value; whereas, Mr. Ricardo has repeatedly informed his reader that he utterly rejects the possibility of any such measure. Thus (at p. 10, edit. 2d), after laying down the _conditio sine quâ non_ under which any commodity could preserve an unvarying value, he goes on to say: "of such a commodity we have no knowledge, and consequently are unable to fix on any standard of value." And, again (at p. 343 of the same edition), after exposing at some length the circumstances which disqualify "any commodity, or all commodities together," from performing the office of a standard of value, he again states the indispensable condition which must be realized in that commodity which should pretend to such an office; and again he adds, immediately, "of such a commodity we have no knowledge." But what leaves this mistake still more without excuse is, that in the third edition of his book Mr. Ricardo has added an express section (the sixth) to his chapter on value, having for its direct object to expose the impossibility of any true measure of value. Setting aside, indeed, these explicit declarations, a few words will suffice to show that Mr. Ricardo could not have consistently believed in any standard or measure of value. What does a standard mean? _Phæd_. A standard is that which stands still whilst other things move, and by this means serves to indicate or measure the degree in which those other things have advanced or receded.