Progress in the Good: a Defense of the Thomistic Unity Thesis
Journal of Moral Theology, Vol. 3, No. 1 (2014): 147-174 Progress in the Good: A Defense of the Thomistic Unity Thesis Andrew Kim HE UNITY THESIS refers to the view that a single virtue can- not be possessed in isolation from the other virtues.1 It is a thesis with a long and complex history. Socrates is already in a defensive posture when he first defends the thesis againstT the commonsense point of view espoused by Protagoras in the early dialogues.2 Plato, Aristotle, the Stoics, Augustine, and Aquinas all affirm versions of the thesis that, as Alasdair MacIntyre notes, “differ… from each other in a number of important ways.”3 Whatever historical interest it may have today, the unity thesis is al- most universally rejected by contemporary ethicists.4 Though cri- tiques of the unity thesis are manifold and cannot be summarized under one head, the common denominator of these critiques may be stated as follows: if the unity thesis is true, then no one is virtuous. This is because the unity thesis appears to totalize virtue attribu- 1My focus throughout is on the cardinal virtues: prudence, justice, temperance, forti- tude. 2 Protagoras 359 b-c. See T. Penner, “The Unity of Virtue,” The Philosophical Re- view 82 (1973): 35-68; “What Laches and Nicias Miss—And Whether Socrates Thinks Courage is Merely a Part of Virtue,” Ancient Philosophy 12 (1992): 1-27; P. Woodruff, “Socrates on the Parts of Virtue,” Canadian Journal of Philosophy, Sup- plementary volume, 2 (1976): 101-16; T.H. Irwin, Plato’s Moral Theory (Oxford: Oxford University Press, 1977), 86-90; M.
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