Mill’s “all useful and agreeable things” presents a marked contrast to this in spirit. Aristotle’s “useful” means “what subserves the final good” (πρὸς ἀγαθὴν ζωήν), while Mill’s means “things that give sensations of comfort or pleasure.” Thus Aristotle’s wealth is necessarily limited, while Mill’s is unlimited, since, as Barker observes, “only an infinity of wealth can satisfy an infinity of need.”546
It will be seen from the following discussion, however, that Aristotle includes more than “necessary things” in his category of economic wealth.
He does not specify “material things,” as does Mill, but it seems probable that this is his meaning.547 In all the passages where he enumerates the different kinds of wealth, only material things are included, except slaves, who are counted as mere tools.548 One of these passages specifically excludes intellectual wealth by defining property as a “separable instrument.”549 The use of the term for value (ἀξία) probably implies the same limitation.550
Though Aristotle does not mention exchange value specifically, it is clearly implied in his definition. “Things useful for the association of a state” and things “capable of accumulation” must have exchange value, thus excluding illimitable utilities such as air and light.551
His use of κτῆμα, “possession,” and his recognition of cost of production and economic demand as the main factors in determining value,552 are further evidence of this. Moreover, as seen above, in the Ethics, he clearly makes exchange value an attribute of all wealth.553
From our comparison of the two definitions, then, it is evident that, though Aristotle is antithetical to Mill in putting the ethical interest first, and though his definition is not so scientifically specific, yet the two agree in recognizing the qualities of materiality, exchange value, and possibility of accumulation as necessary attributes of wealth. We shall see below,