When I wrote After Virtue, I was already an Aristotelian, but not yet a Thomist… I became a Thomist after writing After Virtue in part because I became convinced that Aquinas was in some respects a better Arostotelian than Aristotle, that not only was he an excellent interpreter of Aristotle’s texts, but that he had been able to extend and deepen both Aristotle’s metaphysical and his moral enquiries. And this altered my standpoint in at least three ways. In After Virtue I had tried to present the case for a broadly Aristotelian account of the virtues without making use of or appeal to what I called Aristotle’s metaphysical biology. And I was of course right in rejecting most of that biology. But I had now learned from Aquinas that my attempt to provide an account of the human good purely in social terms, in terms of practices, traditions, and the narrative unity of human lives, was bound to be inadequate until I had provided it with a metaphysical grounding. It is only because human beings have an end towards which they are directed by reason of their specific nature, that practices, traditions, and the like are able to function as they do. So I discovered that I had, without realizing it presupposed the truth of something very close to the account of the concept of good that Aquinas gives in question 5 in the first part of the Summa Theologiae.
What I also came to recognize was that my conception of human beings as virtuous or vicious needed not only a metaphysical, but also a biological grounding, although not an especially Aristotelian one. This I provided a good deal later in Dependent Rational Animals, where I argued that the moral significance of the animality og human beings, of rational animals, can be understood only if our kinship to some species of not yet rational animals, including dolphins, is recognized. And in the same book I was also able to give a better account of the content of the virtues by identifying what I called the virtues of acknowledged dependence. In so doing I drew on Aquinas’s discussion of misericordia, a discussion in which Aquinas is more at odds with Aristotle than he himself realized.
MacIntyre, Alasdair, After Virtue: a study in moral theory. Third edition with a new prologue (Duckworth, 2007; 1st ed. 1981, 2nd ed. 1985), s. vii-ix. Dette er henta frå prologen som er skrive til denne tredje utgåva.