II. Aquinas on Human Nature

Aquinas’ account of human nature properly begins with his Aristotelian conception of souls. In this regard, two points are especially important. First, Aquinas takes a soul to be “the first principle of life in those things in our world which live.”Footnote ¹ Living things are thus described as animated or ensouled (soul =animus): all living things possess a soul, and its soul is that in virtue of which it is alive. For Aquinas as for Aristotle, the line which separates living beings from non-living beings is precisely the line which separates those things which are endowed with souls from those things which are not. Second, a thing's soul is not merely that which gives it life: a thing's soul makes it to be what it is. In Aristotelian terms, a soul is the “actualization of an organized physical body.”Footnote ² As Aristotle goes on to explain in the following passage, this definition rests upon a distinction between two sorts of actuality:

The operative distinction here is that between a (latent) capacity for some sort of activity and the actualization of this capacity. Thus, for example, someone is a violinist because he or she has the capacity to play the violin with a high degree of competency. Since I do not possess this capacity, I am not a violinist. I am at best a potential violinist, since with time and practice I might be able to cultivate this capacity. Because one is a violinist in virtue of this capacity, one does not cease being a violinist when he or she ceases to be engaged in this capacity. At the same time, Aristotle thinks that one who is engaged in this capacity is a violinist in a deeper and truer sense than one who is merely capable of doing so, thus his distinction between first and second actuality: a sleeping violinist is a first-actual (or actual₁) violinist, while one who is engaged in this activity is a second-actual (or actual₂) violinist. Note, moreover, that a thing's soul does not merely provide it with its defining capacity: its soul is identified with its defining capacity. Thus Aristotle suggests that if an eye were a complete organism, then its capacity for sight would be its soul, and if it were lose this capacity it would remain an eye in name only.Footnote ⁴

To sum up what has been said thus far, an object's soul is that in virtue of which it is alive, and it is that which determines its generic manner of life, where each living being falls into one of three general categories: it is either a plant, a (non-rational) animal, or a human being. Thus a plant's soul is its capacity for growth, nutrition and reproduction, an animal's soul is its capacity for sensation and locomotion, and a human being's (rational) soul is one's capacity for reason and understanding. Although all living things are endowed with souls, Aquinas contends that only human souls are capable of existing apart from the human beings of which they are the souls. This is because the actualization of our defining capacity (understanding) is not contingent upon the presence of matter. It is abundantly clear that a plant's capacity for nutrition and reproduction cannot exist apart from certain of its bodily parts, and this is no less true of an animal's capacity for sensation and locomotion. For Aquinas, as for Aristotle, it is equally clear that it is possible for understanding to occur in the absence of matter. For they both take God to be a rational being who is not partly composed of matter. Since one's soul is identical with this capacity, Aquinas contends that it is possible for one's soul to exist apart from the human being of which it is the soul. A rational soul is thus an ens per se, a substantial being in its own right.

Of course it is one thing to say that it is possible for some manner of understanding to occur in the absence of matter, and quite another to say that our understanding is presently grounded in a reality which is devoid of matter. Here again, it is one thing to say that a rational soul is a substantial reality, and quite another to say that it is an immaterial substance. Since our souls are that in virtue of which we are able to understand, it is fitting that Aquinas’ argument to this effect is grounded in the nature and scope of our understanding. Thus Aquinas:

The main idea here is relatively straightforward: since our knowledge of particulars includes an understanding of their natures, this knowledge involves the cognitive reception of their forms or essences. If the seat of such knowledge were itself material, it would inevitably be more receptive to some forms than others, since different sorts of matter will always assume some forms more readily than others. Since our intellects are equally receptive to all manner of such forms, these powers must be grounded in a substance which is devoid of matter, which is to say that our souls are incorporeal as well as subsistent.

Having established that a human soul is a substantial being in own right, the question arises as to how we are related to our souls. Aquinas is adamantly opposed to Plato's contention that we are identical with our souls, i.e., that we are souls which merely use bodies. Though we certainly have souls, we cannot be souls because there are things which we do (e.g., see and hear) which a soul cannot do on its own. He thus concludes that since “sensation is an operation of man, but not proper to the soul, it is clear that man is not only a soul, but something composed of soul and body.”Footnote ⁶ Aquinas further contends that Plato's position cannot account for the substantial nature of human beings. He thus observes that “if soul inhabited body like a sailor his ship the union of body and soul would be accidental, and when death separated them it wouldn't be the decomposition of a substance, which clearly it is.”Footnote ⁷ On his view human beings are composite substances: each of us is endowed with a rational soul which has been substantially united to a living body, so that each of us is the substantial product of this union. The crucial difference here between Plato and Aquinas is grounded in their competing accounts of the soul's modal properties: on Plato's account one's soul is only contingently or accidentally related to one's body, while on Aquinas’ account each rational soul is essentially the soul of some particular human being, so that it is essentially united to a particular human body.

Can Aquinas consistently maintain, first, that it is an essential feature of each soul that it be united to a particular human body, and second, that it is possible for a soul to exist apart from this body? I think that he can. Aquinas contends that in such a case a soul will exist in a radically incomplete and imperfect manner: incomplete because it lacks a complete specific essence of its own (since it must ever remain the soul of some human being), and imperfect because it has been cut off from its normal mode of cognition (which depends upon the reception of sensible images or “phantasms” by way of the bodily senses). In other words, though he denies that one's soul is ontologically dependent upon its union with one's body, he nevertheless insists that it is functionally and teleologically dependent upon such a union. For apart from this union it cannot operate in accordance with its ordinary mode of cognition, and apart from this union it is incapable of fulfilling its inherent purpose or telos, which is to be (a) substantially united to a human body, and so (b) the soul of a complete human being.

I thus conclude that Aquinas can consistently maintain that is possible for our souls to survive the death of the body and the dissolution of the soul/body union. Of course it is one thing to say that our souls will continue to exist after we have died, and quite another to say that we will do so. In what remains of this paper we will examine whether Aquinas is in a position to affirm this latter proposition. As we shall see, it looks as if Aquinas wants to have his cake and to eat it, too. For though he rejects Plato's thesis that we are contingently embodied souls in favor of the thesis that we are soul/body composites, he is wont to say that we can exist for a time as disembodied souls.

III. Aquinas on Death and our Prospects for Immediate Survival

What happens to us when we die? As we have seen, Aquinas believes that death brings about the dissolution of the soul/body union. He thus quotes with approval the Preacher's observation that upon death “the dust returns into its earth from whence it was; and the spirit returns to God Who gave it.”Footnote ⁸ Aquinas contends that our souls will continue to exist in the absence of our bodies, albeit in a highly incomplete and imperfect manner. It is important to add, moreover, that he takes this separation to be temporary, since he believes that this union will be restored at the General Resurrection. Thus in his commentary on Paul's First Letter to the Corinthians Aquinas writes:

For Aquinas it is inconceivable that our souls should continue for ever in such an unnatural state, and so he concludes that our hope for life in the world to come rests entirely in the resurrection of our bodies. Even so, what are we to think of those who have already died? Are we to believe that there is some sense in which they continue to exist? Should we say, for example, that Abraham exists? Or must we say instead that he does not presently exist, though a spiritual remnant of him exists (his soul), and though his existence will eventually be restored at the resurrection? As we shall see, Aquinas appears to be of two minds on this question. For while he is on record as affirming our continued existence, he is evidently committed to the denial of this proposition, and he appears to have explicitly done so on several occasions.

1. The Affirmation

As a Christian theologian Aquinas is unquestionably committed to our continued existence during the interim period between death and the General Resurrection. We see this perhaps most clearly in his commentary on Articles Five and Nine of the Apostles’ Creed. Article Five is concerned with Christ's descent into the underworld and also with his subsequent resurrection. Aquinas’ discussion of this article begins with the observation that Christ's death, like the death of all human beings, involves the separation of his body and soul. He subsequently attempts to explain why it was fitting for Christ's post-mortem existence to have continued in this manner. His first reason pertains to Christ's intention to share fully in our suffering. Speaking of Christ, Aquinas writes:

Although this discussion of punishment and redemption begins with the plight of disembodied souls, by the end of this passage it is the holy fathers and indeed all men who are held captive in the underworld. That is, by the end of this passage he is speaking in terms of the continued existence of those who were once alive rather than in terms of the continued existence of their souls. He maintains this emphasis in his account of Christ's second reason for descending into hell, namely, “that he might perfectly deliver all of his friends,” that is, those who had died in hope of his coming as well as those who were yet alive. Thus Aquinas continues,

Here again, Aquinas is implying that Christ has friends both on earth and in the underworld. Since he can hardly deliver friends who do not exist, the implication of this passage is clear. We must say, for example, that Abraham himself exists in the underworld, and not merely that his soul exists there. Since it is also true that Abraham's body was not present in the underworld, Aquinas evidently believes that during this period Abraham exists as a disembodied soul.

We find a similar emphasis in Aquinas’ commentary on the Ninth Article of the Apostles’ Creed, which is centered around the words “I believe in the Holy Catholic Church.” He begins by observing that the Holy Church is the assembly of the faithful. He subsequently points out that one part of this assembly exists on earth, one part exists in purgatory, and one part exists in heaven.Footnote ¹² This obviously implies that the faithful departed are still very much in existence, since it makes little or no sense to say that one's soul is a member of this assembly. And while it is true that Aquinas sometimes identifies the denizens of purgatory and heaven as souls,Footnote ¹³ it is nonetheless important that he does not restrict himself to this manner of speaking. For in speaking of these disembodied souls as men, as his friends, as the holy fathers and as the members of Holy Church, he is committing himself to the thesis that the faithful departed continue to exist, and that they continue to exist as disembodied souls.

2. The Denial

Although Aquinas evidently believes that we will continue to exist during the interim period between our death and the General Resurrection, this thesis appears to be inconsistent with his account of our nature as soul/body composites. If we are soul/body composites then we are not identical with our souls, so even if it is possible for our souls to continue existing after we have died, it is evidently impossible that we should continue to exist. For if we are not our souls now then we shall never be our souls, and so whatever does continue to exist after we have died, it will not be us. Indeed Aquinas says as much on several occasions. Consider the following three passages:

In each of these passages Aquinas seems to deny our continued existence during the interim period. Though we are substances and our souls are substances, we are not our souls. Our relationship to our soul is one of composition rather than identity. That is, we are partly composed of our souls, and partly composed of our bodies. We are indeed the product of their substantial union. The implication of this position is almost too obvious to warrant stating: since each of us is the substantial product of this union, its substantial dissolution must result in our substantial destruction. Or if this dissolution is itself temporary, it must at least constitute the temporary suspension of our existence.

3. Resolution

Will we continue to exist during the interim period between our death and the General Resurrection? Aquinas appears to be telling us both that we will and also that we will not. What should we make of this? It is of course possible that Aquinas’ position is simply contradictory. And yet I think it is unlikely that he would have contradicted himself in such an obvious manner, particularly in connection with a doctrine which is of central importance to the Christian gospel and our hope for life in the world to come. In what remains of this paper I would like to consider two ways of making sense of his position which avoids this charge. The first proposal accepts the implication that if we are soul/body composites then we cannot exist (even for a time) as disembodied souls, while the second proposal rejects this implication.

First proposal . Suppose that it really is a mistake identify a disembodied soul with the human being who was once partly composed of this soul. Although Abraham's soul continues to exist during this period, strictly speaking, Abraham does not, since Abraham is not his soul. Even so, we might continue to speak of this soul as though it were Abraham. Aquinas appears to take just this approach in connection with a dispute surrounding the practice of prayers to the saints. In the context of discussing the question of whether the saints in heaven pray for us, he considers several reasons for concluding that they do not. The last of these reason runs as follows:

Here is Aquinas’ subsequent response to this objection:

Note that Aquinas’ response does not challenge the thesis that the soul of Peter is not Peter. Indeed he appears to concede the implication that (strictly speaking) it is Peter's soul rather than Peter who offers prayers on our behalf. At the same time, he appears to be suggesting that we are justified in referring to this soul as though it were Peter in virtue of its metaphysical continuity with Peter both before his death and after his bodily resurrection.Footnote ¹⁷

There is something quite odd about this way of making sense of Aquinas’ position. For one thing, it is a matter of Christian doctrine that immediately following our deaths we will stand before the judgment seat of Christ and render an account of our lives. Depending upon the outcome of this judgment, we will subsequently await the resurrection of our bodies either in a state of abject misery and isolation from God (hell), in a state of temporary, redemptive punishment which is tempered by faith, hope and love (purgatory), or in a state of blissful glory (heaven). In addition, we are repeatedly advised to pray for those belong to the second category, and to pray to those who belong to the third. Finally, with the Apostles’ Creed and the Nicene Creed we believe that we are presently in communion with the faithful departed, which is to say that we are in communion with those who were once alive, and not merely with their souls. None of this is possible without their continued existence.

In addition, consider how this scenario is likely to seem from the vantage point of one of these souls. Even if Peter is not identical with his soul, from the vantage point of his soul it will very likely seem for all the world as if it [better: he] was once a complete human being, just as it will likely seem to the resurrected Peter that after his death he existed for a time as a disembodied soul. Since our disembodied souls will be experiencing the moral consequences of our actions, we have no choice but to expect a high degree of psychological continuity here. Are we really willing to say that this sense of personal continuity is delusory? I don't think so. And yet suppose that it is. As a center of consciousness, understanding and volition, we would have no choice but to regard Peter's disembodied soul as a person (which is why we cannot properly refer to such as soul as an ‘it’). And though this soul would be a person, it would not be personally identical with Peter either before his death or after his resurrection, which would mean that multiple, psychologically continuous persons are associated with each rational soul. Finally, wouldn't this commit us to saying one person is being held accountable for the sins of another? And isn't this simply unjust? I certainly hope there is a way of understanding Aquinas which avoids these implications. And so there is.

Second Proposal. Though Peter is not his soul, it is still possible for Peter to exist for a time as a soul. That is, it is possible for one to exist for a time as a disembodied soul without having to say that one is his soul. Can Aquinas really have it both ways? Can he consistently say both (a) that we are soul/body composites (and hence not souls), and (b) that we can exist for a time as disembodied souls? Following Aristotle, Aquinas thinks that he can. Consider the following passage:

In this passage Aquinas is wrestling with the Apostle Paul's distinction between the “inner man” (which is being daily renewed by the grace of God) and “outer man” (which wasting away).Footnote ¹⁹ In the passage which immediately follows his use of this distinction, Paul writes about the afterlife in a manner which sound surprisingly Platonic:

I say that this passage sounds “surprisingly Platonic” for two reasons. First, Paul seems to be identifying us with the “inner man” for which our bodies serve as “earthly tents,”Footnote ²¹ and from which we can readily leave in order to be at “home with the Lord.” This way of speaking is apparently at odds with his assertion (in 1 Cor. 15) that apart from the resurrection there is no hope for life in the world to come. Second, Paul seems to be suggesting that we are better off without our bodies, grounded as they are in the vastly inferior realm of the visible, corruptible and transient.Footnote ²² This suggestion is at odds with our conviction that disembodied existence is inimical to the flourishing of our natures.

How does Aristotle's discussion of parthood enable Aquinas to come to grips with the Apostle Paul's nascent Platonism? Following Aristotle, Aquinas is saying that it sometimes makes sense to associate a composite with one of its parts. In particular, he argues that we can associate a composite with one of its parts when this part functions as the ruling principle for the whole. And such is the case, he thinks, with respect to the intellectual part of a human being, i.e., the part which stands before the judgment seat of Christ and which Paul refers to as the “inner man”.

I would like to suggest that the chief claim here is not a claim about identity, but rather one about essential parthood. In particular, Aquinas is claiming that our intellectual part is more central to our existence than our bodily part, and hence that we can be deprived of the latter without ceasing to exist, but not the former. This is not a point about identity because the “inner man” and the “outer man” are not two distinct human beings. Instead, these expressions identify distinct parts or aspects of a particular human being, with the added claim that the first is more central to our existence than the latter, so that it is possible for us to exist (at least for a time) without the latter, but not without the former. That is, we can exist for a time as disembodied souls because our souls have a much deeper hold on who we are than our bodies. Does this commit Aquinas to Plato's thesis that we are ultimately identical with our souls? In a word, No. Because I am a soul/body composite I am not presently identical with my soul. And because I am not presently identical with my soul I shall never be identical with my soul. It is still possible for me to exist for a time as a soul, provided that my soul is essential to my existence in a way that my body is not. Note, moreover, that in this disembodied state I will remain numerically distinct from my soul, since I will continue to be endowed with properties which my soul must lack, namely, properties which require a body. Since it is impossible for an immaterial being to play baseball or write a paper on a laptop computer, my soul will never have the property of having performed these activities. Since I do have these properties, I will continue to have them as long as I exist. How then will I be related to my soul, if not by way of identity? The answer is readily forthcoming: I will be composed of my soul. That is, I will be (for a time) wholly composed of that with which I was once partly composed, and of that with which (following the resurrection) I will once again be partly composed.

Let us now briefly return to the three passages cited earlier in connection with Aquinas’ apparent denial of our continued existence during the interim period between our death and the General Resurrection:

The first two passages are obviously consistent with the position I have just defended. If we are soul/body composites (rather than souls), then it does not follow that we shall continue to exist immediately after we have died. But neither does it follow that we cannot continue to exist. Although Abraham is not his soul, it does not follow that he cannot exist for a time as a soul, and so it does not follow that Abraham does not exist during the interim period between his death and the General Resurrection.

The third passage is trickier, for here Aquinas is telling us that death results in the decomposition of a substance. That is, death results in the dissolution of the substantial soul/body union which constitutes each living human being, i.e., the soul/body union which each of us is. Is this passage compatible with the view which I have been defending? I think that it is. Even if it is possible for us to exist as disembodied souls, we must reject the thesis that we are identical with our souls, since we will continue to be endowed with properties which our souls must lack. The same holds true for the soul/body union which exists at present: there are things which are true of us which will never be true of this substantial union. For one thing, this composite substance will never exist without a body, even if we shall exist for a time without a body. So if is possible for one to exist as a disembodied soul, such an individual is no more identical with the substantial union of his body and soul than he is identical with his soul alone. And this means that we can say (with Aquinas) that death results in the decomposition of a living substance, without having to say that this event constitutes the termination of our existence. Does this commit us to saying that we are only contingently human? It does not. We are essentially human in the same way and for the same reason that our souls are essentially human: just as it is functionally and teleologically essential for our souls to be united to a human body, it is similarly essential for us to be partly composed of a human body. Although it is possible for us to exist for a time as disembodied souls, this will be a radically incomplete and inferior manner of existence for us as well as for our souls. This, in turn, helps to explain why death continues to be a great enemy which will not have been destroyed until the Last Day, when we will be restored to complete existence through the resurrection of our bodies.

III. Conclusion

In this paper I have argued that Aquinas can consistently say both (a) that we are soul/body composites, and (b) that we will exist without bodies during the interim period between death and the General Resurrection. Because our souls are essential to us in a way that our bodies are not, Aquinas can say that it is possible for one to exist for a time as a soul without having to say (per impossibile) that one has become his soul.

I hope it is clear that the significance of this conclusion extends far beyond the consistency of Aquinas’ writings. For it looks as if orthodox Christianity as a whole is committed to the thesis that we are soul/body composites, since what the Church Fathers have proclaimed in connection with Christ's humanity (namely, that he is composed of a human body and a rational soul), must also apply to ours.Footnote ²⁴ What's more, traditional Christianity is no less committed to the thesis we will continue to exist after we have died. In addition to doctrines concerning purgatory and the communion of the saints, there is the so-called harrowing of hell, in which Christ is said to have descended to the dead (Apostles’ Creed) and to have preached the good news to “spirits in prison” (1 Pet. 3.19–20); there is the biblical claim that we will face judgment immediately after we have died (Heb. 9.27); there is Paul's claim that to be absent from the body is to be present with the Lord (2 Cor. 5:1–10); and there are Christ's words of comfort to the good thief (Lk 23.39–43). It thus appears that believers are generally committed both to the thesis that we are soul/body composites, and also to the thesis that we will continue to exist during the interim period between our death and the General Resurrection. Since the truth of orthodox Christianity quite literally depends upon the consistency of these propositions, and since their ultimate consistency is far from obvious, Aquinas’ contribution to this discussion is far from trivial.