True, Aristotle sees that the exchange value of commodities underlies their prices: “ὅτι ὴ ἀλλαγη ἥν πρὶν τὸ νόμισμα ἔιναι, ὁῆλον· διαφέρει γὰρ οὐδὲν ἡ εί κλίναι πέντε ἀντι οἰκίας, ἣ ὅσου αὶ πέντε κλῖναι.” (“It is clear that exchange existed before coin. For it does not make any difference whether you give five beds for a house, or as much money as five beds are worth”). On the other hand, since commodities acquire only in price the form of exchange value with respect to one another, he makes them commensurable through money. “Διὸ δεῖ πάντα τετιμῆσθαι· οὕτω γὰρ ἀεὶ ἔσται ἀλλαγὴ, εἰ δὲ τοῦτο, κοινωνία. Τὸ δὴ νόμισμα ὥσπερ μέτρον σύμμετρα ποιῆσαν ἰσάζει, οὔτε γὰρ ἃν μὴ οὔσης ἀλλαγῆς κοινωνία ἡν, ὄυτ ‘ἀλλαγὴ ἰσότητος μὴ οὔτ’ ἰσότης, μὴ οὔσης συμμετρίας.” (“Therefore all has to be appraised. In that way exchange may always take place, and, with it, society can exist. Coin, like measure, makes everything commensurable and equal, for without exchange there would be no society, without equality there would be no exchange, and without commensurability, no equality.”) He does not conceal from himself that these different objects measured by money are entirely incommensurable quantities. What he is after is the common unit of commodities as exchange values, which as an ancient Greek he was unable to find.