 Plato’s concern with ‘right measure’ in a sense that is relevant for ethics is, of course, not confined to his late work. It shows up rather early. Already in the Gorgias, Socrates blames Callicles for the undisciplined state of his soul, and attributes it to his neglect of geometry, (508a): “You’ve failed to notice that proportionate equality (geometrikê isotês) has great power among both gods and men.” But it is unclear whether this expression is to be taken in a more than metaphorical sense; it is, at any rate, not repeated anywhere else in Plato’s earlier work. Numbers are treated as paradigmatic entities from the middle dialogues on, and in the Protagoras (156c–157e), Socrates maintains that virtue is ‘the art of measuring’ (metrêtikê technê) pleasure and pain. But nothing further is made of that suggestion; the dialogue ends in aporia about the nature of virtue (161c–d) — a fact that strongly speaks against the attribution of a kind of ‘enlightened hedonism’ to Plato, as certain interpreters are wont to do. There is no indication that Plato takes seriously the idea of a ‘quantification’ of the nature of the virtues in his middle dialogues. If mathematics looms large, then, it is as a model science on account of its exactness, the stability of its objects, and their accessibility to reason. A systematic exploration of the notion that measure and proportion are the fundamental conditions of goodness is confined to the late dialogues. Apart from the Timaeus’ emphasis on a precise cosmic and mental order, there is a crucial passage in the Statesman (283d–285c), where the Eleatic Stranger distinguishes two kinds of ‘art of measurement’. The first kind is the ordinary measuring of quantities relative to each other (‘the great and small’). The second kind has a normative component; it is concerned with the determination of ‘due measure’ (to metrion). The latter is treated with great concern, for the Eleatic Stranger claims that it is the basis of all expertise, including statesmanship, the very art that is the subject of the dialogue itself, (284a–b): “It is by preserving measure in this way that they produce all the good and fine things they do produce.” His point is that all good productions and all processes of generation that come to a good end presuppose ‘right measure’, while arbitrary quantities (‘the more and less’) have no such results. The Eleatic Stranger therefore suggests the separation of the simple arts of measuring from the arts concerned with due measure, (284e): “Positing as one part all those sorts of expertise that measure the numbers, lengths, depths, breadths and speeds of things in relation to what is opposed to them, and as the other, all those that measure in relation to what is in due measure (to metrion), what is fitting (to prepon), the right moment (to kairion), what is as it ought to be (to deon)—everything that is removed from the extremes to the middle (meson).” This distinction is not applied in the Statesman itself, except that due measure seems to be presupposed in the final definition of the statesman as a ‘kingly weaver’, weaving together the fabric of the state by combining the aggressive and the moderate temperaments of the population so as to produce a harmonious citizenry (305e– 311c). But mathematics is not mentioned as the condition of the ‘mixing of the citizens’ characters’. 