If Tolkien’s hypothesis of non-naturally but voluntarily incarnate angelic beings captures something of the “freedom” but also the problematic character of modern mind-body dualism, his fictional anthropology of Elves and Men, by contrast, seems to channel the hylomorphic (matter-form) theory of body and soul propounded by Aristotle and Aquinas. According to this tradition, the human soul is not extrinsically related to the body, as per the soul-body dualism of Plato and Descartes, but is the formal, final, and efficient cause of the human body, the form and actuality through which, by which, and for which the body has its very being as a body (Summa Theologiae 1.76.1). It follows from this, for both Thomas and Tolkien, that, on the one hance, the soul (or what the Elves call “fëa”), is incorporeal and incorruptible and thus capable of existing from the body (see, for example, Summa Theologiae 1.75.2 and Morgoth’s Ring 223, 245, and 330). (Although Tolkien says in one note that hröa and fëa are “roughly but not exactly equivalent to ‘body’ and ‘soul’” [Morgoth’s Ring 330], he does not specify how they are in fact different, and elsewhere he simply asserts that fëa “corresponds, more or less, to ‘soul’; and to ‘mind’” in its immaterial aspects .)
On the other hand, we find both Thomas and Tolkien eager to maintain that the soul, its ability to exist apart from the body notwithstanding, nevertheless does not constitute the whole of man. Thomas argues this position in Summa Theologiae 1.75.2, and we find Tolkien in basic agreement when he writes, for example, that when a man receives an injury it is not merely the soul-principle, the “Indweller,” that suffers the wound, but “Man, the whole: house, life, and master” (Morgoth’s Ring 353). As Tolkien explains elsewhere, the soul is indeed the principle or source of “identity” (227), being both “conscious” and “self-aware,” and yet he also adamantly affirms the body to constitute an integral and necessary part of the “self” of the person (349). St. Thomas also argues that, however much the soul may be able to go on existing apart from its body, it still remains greatly dependent on its body in order to carry out its own proper acts of knowing, as this requires the operation of the bodily powers of sensation and imagination (Summa Theologiae 1.84.7). Tolkien may be seen to echo this point when he says that, although it is the soul that has “the impulse and power to think: enquire and reflect,” its mental processes, like Thomas’s incarnate soul, are nevertheless “conditioned and limited by the co-operation of the physical organs” of the body (Morgoth’s Ring 349).
 For an alternative (and somewhat underdeveloped) reflection on Tolkien’s anthropology in light of St. Thomas’s philosophy of man to the one I am offering here, see Nimmo, “Tolkien and Thomism: Middle-earth and the States of Nature.” As the title of Nimmo’s article suggests, the author takes up the five states of nature distinguished by Aquinas, namely the “hypothetical” states of (1) pure nature and (2) integral nature, and the “historical” states of (3) innocence or original justice, (4) fallen nature, and (5) restored or repaired nature, and attempts to correlate these with the different species of rational beings and their respected states found in Tolkien’s mythology.
 For Aristotle’s hylomorphic doctrine of the soul, see book two of his On the Soul. For an explanation and defense of Thomas’s hylomorphic anthropology in light of some of its contemporary criticisms, see Klima, “Man = Body + Soul: Aquinas’s Arithmetic of Human Nature.”