Aquinas's Ethics: Metaphysical Foundations, Moral Theory, and Theological Context

two. Soul and Body

two Soul and Body In the last chapter we presented an overview of Aquinas’s metaphysics . We focused on the hierarchy of being and the distinction between actuality and potentiality, not just because it proves central to understanding how Aquinas thinks generally about the connection between God and creatures, but also because it gives us special insight into how he thinks of human beings and their nature. A species’ unique combination of potentiality and actuality locates that species on the hierarchy between pure actuality—God—and pure potentiality—prime matter. It would seem natural, then, for the concept of humans as unique combinations of actuality and potentiality to play a central role in Aquinas’s account of our nature—and it does. We constitute the bridge between material and immaterial beings because we possess both the actuality inherent to intellective beings and the potentiality characteristic of material creatures. Fully understanding Aquinas’s account of human nature, however, requires seeing humans not just generally as composites of actuality and potentiality, poised between the intellectual and physical realms, but more particularly as composites of matter and form. We turn in this chapter to a closer examination of what are sometimes called our “metaphysical parts”: form and matter, which are often equated with soul and body.1 Aquinas holds that the rational soul is the form (more specifically, the substantial form) of the physical human being. This does not mean, however, that the human body is reducible simply to matter. As we will 27 see, Aquinas believes that there is one and only one substantial form per individual substance. The living human body is, therefore, in a very important sense identical to the particular human being. Thus, Aquinas consciously sets up his account of human nature in opposition to a more traditional form of substance dualism, according to which soul and body are both separable and complete in their own right. Aquinas’s account of human beings is also his account of human persons. This underscores the extent to which he sees our intellectual and physical nature as integrated and further demonstrates our connection to God, whom Aquinas describes as the paradigm case of a person. We are created in God’s image, and one of the central ways in which humans mirror God is by being ourselves persons, complete with intellects and wills. The connection between human beings, persons, intellects, and wills has significance that stretches beyond our mere metaphysical makeup, however; it reaches all the way to our moral status. As we saw in chapter 1, the extent to which something actualizes its natural potentialities determines its excellence or goodness as a member of that species. After getting clearer in this chapter about Aquinas’s general understanding of human nature, in chapter 3 we will examine the specific way in which he claims that human capacities and the human function relate to our being and our goodness. For the connection between what human beings are and what they do, it is necessary to examine more closely certain capacities integral to decision-making and the flourishing moral life—in particular, the rational capacities of both the intellect and the will (Aquinas refers to the latter as the “rational appetite”). Aquinas agrees with Aristotle that the function of a rational animal is “the life of activity expressing reason well.” He also holds, however, that human beings are created in God’s image. This fact grounds every interesting and important further fact about us and is key to Aquinas’s action theory and ethical theory. Soul As discussed in chapter 1, humans fall at the exact point on the continuum where the class of intellectual substances intersects with the class 28 Aquinas’s Ethics of material substances—where intellectual substances end and physical bodies begin.2 Possessing characteristics of both material and immaterial beings, we cannot properly be classified as either, a point made clear in the structure of the Summa theologiae’s discussion of creatures. Aquinas orders his treatise on creation by beginning with “purely spiritual” creatures (that is, immaterial substances such as angels), moving on to “purely corporeal” creatures (material substances such as tigers and granite), and saving for last the complicated case of the creature “composed of corporeal and spiritual parts, which is the human being.”3 Human beings are the only substances that possess both intellects and matter: no other intellective substance has a...