The ancestor of one of these sets of answers is Plato, for whom as we have seen the virtues are not merely compatible with each other, but the presence of each requires the presence of all. This strong thesis concerning the unity of the virtues is reiterated both by Aristotle and Aquinas, even though they differ from Plato – and each other – in a number of important ways. The presupposition which all three share is that there exists a cosmic order which dictates the place of each virtue in a total harmonious scheme of human life. Truth in the moral sphere consists in the conformity of moral judgment to the order of this scheme.
There is a sharply contrasting modern tradition which holds that the variety and heterogeneity of human goods is such that their pursuit cannot be reconciled in any single moral order and that consequently any social order which either attempts such a reconciliation or which enforces the hegemony of one set of goods over all other is bound to turn into a strait-jacket and very probably a totalitarian straitjacket for the human condition. This is a view which Sir Isaiah Berlin has urged upon us strenuously, and its ancestry, as we noted earlier, is in Weber’s writings. I take it that this view entails a heterogeneity of the virtues as well as of goods in general and that choice between rival claims in respect of the virtues has the same central place in the moral life for such theories that choice between goods in general does. And where judgments express choices of this kind, we cannot characterise them as either true or false.
The interest of Sophocles lies in his presentation of a view equally difficult for a Platonist or a Weberian to accept. There are indeed crucial conflicts in which different virtues appear as making rival and incompatible claims upon us. But our solution is tragic in that we have to recognise the authority of both claims. There is an objective moral order, but our perceptions of it are such that we cannot bring rival moral truths into complete harmony with each other and yet the acknowledgement of the moral order and of moral truth makes the kind of choice which a Weber or a Berlin urges upon us out of the question. For to choose does not exempt me from the authority of the claim which I choose to go against.
After Virtue, Duckworth Second Edition, pp 142-3