You write often of the loss of Aristotelian metaphysics (specifically as adopted and developed by St. Thomas) and all the modern philosophical "problems" that have arisen as a result. Discussions of God's existence, the mind-body relation, ethics, etc. all become "problematic" when we remove formal and final causality. I find this amazingly effective in answering modern arguments because it is often their metaphysical presuppositions that cause problems in the first place.
My question is: were the concepts of final and formal causality present in the Patristic era? As I understand it, most of the Church Fathers were only marginally (if at all?) influenced by Aristotle, and were typically more dependent on Platonic or Neo-platonic metaphysics. Does this mean that up until the time of Aquinas, when Aristotle is "rediscovered" in the West, that Christian philosophy was incoherent because it depended more on a Platonic metaphysics than an Aristotelian metaphysics?
The answer is no, it was not incoherent, but rather incomplete. When a baby or child is developing, it cannot do everything an adult can do. Yet that is not because the organism is defective, but only because it hasn't yet matured. Thus it is perfectly healthy despite its lack of full development. But when an adult becomes sick or otherwise does not function the way an adult ought to, that is not because the organism is immature but rather because it is positively breaking down or because things are at least temporarily not working together correctly. This is decay or at least damage rather than development. Now ancient Christian theology is like the baby or child. The Scholastic tradition, I would say, is like the healthy adult. Modern theologies which reject Scholasticism and try to substitute for it some post-Scholastic modern metaphysics are like the sick adult. They typically preserve some aspect of the Scholastic inheritance, but take on board novel elements that are incompatible with it and/or leave out aspects without which the preserved ones cannot function. (In my work I have described how Cartesian and Lockean approaches to theological questions exhibit this sort of incoherence. See chapter 5 of The Last Superstition and my book Locke.)
It is important to stress that the more Platonic approach that dominated earlier Christian thought was by no means like the post-Cartesian approaches that defined themselves against Scholasticism. The latter approaches, as I often emphasize, tend toward a mechanistic conception of the natural world. It is not merely that they don’t have the Aristotelian notions of formal and final causality. It is that they self-consciously reject these notions and replace them with the understanding of nature first developed by the ancient Greek atomists (altering the details, of course). There is nothing like that in Platonism or Neo-Platonism. (This is one reason it is very misleading to assimilate Plato’s and Descartes’ views of human nature, as is often done.) Furthermore, there is really no such thing as a purely Platonist or purely Aristotelian tradition in the first place. It is more a question of which tendency dominates. The Neo-Platonist tradition tried to incorporate Aristotle’s insights by “Platonizing” them, and Aquinas takes the insights of the Neo-Platonic and Augustinian traditions and “Aristotelianizes” them. (Consider e.g. the Fourth Way and Aquinas’s use of the notion of “participation.”)
Now, the various problems that I have said afflict modern thought are associated with the mechanistic and positively anti-Aristotelian tendencies specifically. Since there is nothing like that in the earlier tradition, the earlier tradition does not have the same problems. To the extent it did have problems, they are more like the problems a baby has in learning to walk (compare the tentative and inchoate use of Greek philosophical concepts by the early Christian theologians) or an adolescent has when he is just coming out of his childhood but not quite ready for adult responsibilities (compare the excesses of a thinker like John Scotus Eriugena).
Modern theologies which do not endorse novel post-Cartesian metaphysical systems but seek instead to revert to some pre-Scholastic Neo-Platonism might therefore best be described in terms of a third comparison -- not to a child and not to a sick or dying man, but rather to a man going through a midlife crisis. Such a man finds his middle-aged responsibilities tedious and longs to recapture the excitement of youth. Similarly, theologians hostile to Scholasticism and its Aristotelian philosophical basis often complain that it is too dry, systematic, and logic-oriented -- interestingly, they often do not claim that it is false -- and prefer the more mystical and inchoate approach of pre-Scholastic and Neo-Platonic theologians. (Platonism, as I say in The Last Superstition, is “sexier” than Aristotelianism, but also less sober and rigorous.)
Now, a man faced with a midlife crisis might take it as an opportunity to spice up his life a bit in a healthy way -- to rekindle romance with his wife, to supplement the necessary routines of middle age with a return to some of the hobbies he has neglected, or what have you. But he might go instead in an unhealthy direction -- by leaving his wife, neglecting his responsibilities in favor of foolish adventures, etc. In mid-twentieth-century Catholic theology, there was much talk among critics of Scholasticism of going “back to the sources” -- to the early Fathers of the Church and in general to thinkers of the ages before the Scholastic tradition had taken definite shape. If what this means is recalling and reapplying, within the existing tradition, neglected insights from an earlier era, then that is all to the good. But if what it means is chucking out the tradition that the great Scholastics painstakingly worked out in a rigorous and systematic way over the course of centuries, then this is not so good and (as R. R. Reno pointed out in a piece in First Things some time back) it has had some very bad consequences.