Aristotle’s geometrical accounting

This paper comments on Ambrosi’s ‘Aristotle’s geometrical accounting’ (Cambridge Journal of Economics 2018, 42, 543–576). While supporting Ambrosi’s case that Aristotle may well have used geometry to demonstrate accounting equivalence, the paper takes issue with Ambrosi’s specific approach to interpreting Aristotle’s ‘merit or worth’ in terms of income. It is entirely reasonable to understand worth in terms of income. However, Ambrosi implies that worth is determined by market prices; this is inconsistent with Aristotle’s treatment of distributive justice. Rather Aristotle states that relative worth is determined prior to market exchange. In other words, Aristotle seeks to identify the just price to which market prices may or may not correspond. Ambrosi’s own geometrical method is extended to illustrate this point, to provide a geometrical alternative to Ambrosi’s algebraic derivation of the key proposition ‘as builder to shoemaker, so shoes to houses’, and to resolve what Aristotle means by ‘one should not introduce them as terms in a figure of proportion when they are already making the exchange (since otherwise one of the two extremes will have both of the excess amounts) but when they are still in possession of their own products’. Aristotle deserves recognition as the first Western economist and as a Classical economist to boot, in the sense of holding that distribution is determined prior to exchange.