always depends upon the way in which commodities express their own exchange value to each other.
Commodities now confront one another in a double capacity: actually as use- values, ideally as exchange values. The twofold aspect of labor contained in them is reflected in their mutual relations; the special concrete labor being virtually present as their use-value, while universal abstract labor-time is ideally represented in their price in which commodities appear as commensurable embodiments of the same value—substance differing merely in quantity.
The difference between exchange value and price appears to be merely nominal or, as Adam Smith says, labor is the real price, and money the nominal price of commodities. Instead of estimating the value of one quarter of wheat in thirty days of labor, it is estimated in one ounce of gold if one ounce of gold is the product of thirty days' labor. However, far from this difference being merely nominal, all the storms which threaten commodities in the actual process of circulation center about it. Thirty days of labor are contained in a quarter
quantities. What he is after is the common unit of commodities as exchange values, which as an ancient Greek he was unable to find. He gets out of the difficulty by making commensurable through money what is in itself incommensurable, so far as it is necessary for practical purposes, "Τῇ μὲν οὖν ἀληθείᾳ ἀδύνατον τὰ τοσοῦτον διαφέροντα σύμμετρα γενέσθαι, πρὸς δὲ τὴν χρείαν ἐνδέχεται ἱκανῶς." ("In truth it is impossible to make things that are so different, commensurable, but for practical purposes it is permissible.") Aristotle, Ethica Nicomachea, l. 5, c. 8, edit. Bekkeri, Oxonii, 1837.
