"In Greek Ethics, the doctrine of the Right Mean has been developed by Plato (Philebus) and Aristotle (Nic. Ethics II. 6-8) principally, on the Pythagorean analogy between the sound mind, the healthy body and the tuned string, which has inspired most of the Greek Moralists. Though it is known as the "Aristotelian Principle of the Mean", it is essentially a Platonic doctrine which is preformed in the Republic and the Statesman and expounded in the Philebus, where we are told that all good things in life belong to the class of the mixed (26 D). This doctrine states that in the application of intelligence to any kind of activity, the supreme wisdom is to know just where to stop, and to stop just there and nowhere else. Hence, the "right-mean" does not concern the quantitative measurement of magnitudes, but simply the qualitative comparison of values with respect to a standard which is the appropriate (prepon), the seasonable (kairos), the morally necessary (deon), or generally the moderate (metrion). The difference between these two kinds of metretics (metretike) is that the former is extrinsic and relative, while the latter is intrinsic and absolute. This explains the Platonic division of the sciences into two classes: those involving reference to relative quantities (mathematical or natural), and those requiring absolute values (ethics and aesthetics). The Aristotelian analysis of the "right mean" considers moral goodness as a fixed and habitual proportion in our appetitions and tempers, which can be reached by training them until they exhibit just the balance required by the right rule. This process of becoming good develops certain habits of virtues consisting in reasonable moderation where both excess and defect are avoided: the virtue of temperance (sophrosyne) is a typical example. In this sense, virtue occupies a middle position between extremes, and is said to be a mean; but it is not a static notion, as it leads to the development of a stable being, when man learns not to over-reach himself. This qualitative conception of the mean involves an adaptation of the agent, his conduct and his environment, similar to the harmony displayed in a work of art. Hence the aesthetic aspect of virtue, which is often overstressed by ancient and neo-pagan writers, at the expense of morality proper" (Runes, Dictionary of Philosophy).