These four virtues reappear in scholastic philosophy in the guise of the cardinal virtues (Lat. virtutes cardinales): prudence, fortitude, temperance and justice (cf. OED). To talk of 'good' and 'virtue' with respect to Plato and Aristotle is misleading insofar as these terms are inevitably understood in a moral sense. But in the context of these two thinkers' thinking on social life and the constitution of the polity of such living, the 'good' in question is ultimately living well (eu)= zh=n) or doing well (eu)daimoni/a). 'Good' is not a moral quality inhering in a human subject but is always good-for-living-well in society and thus always related to social practices beneficial or detrimental in a social world. Good is always pragmatic good relating to practical affairs or pra/gmata. The goodness of the polis which Plato casts in his Politeia is not that of perfect virtuousness of a city free from sin or morally without blame, but a perfect goodness in the sense that nothing remains to add to the degree of goodness for living well in the polity of such a polis. Likewise, the good citizen of such a polity is the one who is fit for contributing to its well-being.
Phronesis is insight into practical affairs which allows actions to be well-deliberated (eu)/bouloj 428b). It is the sight in which practical affairs come to light, the power of disclosure for how practical affairs show themselves. Such insight is the basis upon which deliberations and decisions are made and must play the leading role in a polis or an individual for it guides the actions either of the whole or its members. In Plato, phronesis is often used synonymously with other terms from which it should, strictly speaking, be distinguished, as Aristotle does. This is apparent in the present context of Book IV of the Politeia, where we read sofi/a (wisdom 427e) at one point, fro/nhsij (practical insight 433b) at another, lo/goj (reason 440b), logismo/j (reasoning 440b, 441b), e)pisth/mh (science, knowledge 444a). With regard to the individual ( i)diw/thj 441c) leading its practical life in the polis, phronesis is attributed to the soul or yuxh/ as one of its aspects. The soul is not some thing residing in the body. Yuxh/ is the name for the being of living beings, z%=a, and denotes not only their principle (a)rxh/) of self-movement, i.e. that they are the starting-points governing their own movements of growth, locomotion, etc., but also that they are open to the world surrounding them through sensuous perception (a)i)/sqhsij) and, in the case of human living beings, also through lo/goj, reason, understanding. With regard to human being, the insight of understanding essentially characterizes human openness to the world.
It was Plato's discovery that what characterizes the specifically human openness to the surrounding world is that it is able to see the looks which beings offer of themselves qua beings. He calls the look or sight of a being its ei)=doj or i)de/a, from the Greek verb i)dei=n, 'to see'. This look of beings in their showing of themselves is not accessible to sensuous perception, but only to the perception of the lo/goj, i.e. to understanding. The word for understanding in Greek, ei)de/nai, is also a form of the Greek verb i)dei=n, 'to see'. Aristotle refines Plato's metaphysical insight in the Aristotelean categories which differentiate the various ways in which the looks of beings can be addressed by the logos. Beings are seen by the understanding with a view to how they stand in the categories of what something is, how it is, how much it is, etc. The sight of human understanding is insight into the sights offered by beings of themselves qua beings. This sight, which is receptive of the sights offered, brings beings to stand for understanding. The sights offered of themselves by beings constitutes their self-showing, their showing-off, their a)pofa/nsij of what they are. This self-showing is their disclosure of themselves qua beings. If this disclosure takes place as a self-showing of beings as themselves, it is true, a)lhqe/j. If it is distorted or only partial, the self-showing is to that extent false, yeu=doj. The look of a being qua being is a well-defined outline seen by human understanding and addressable by the logos, which can carry on a discourse or diale/gesqai about the being concerned.
To be continued...