The resurrection of the body

The problem of ‘gappy’ existence is raised for Aquinas by the Christian doctrine of bodily resurrection, which Aquinas understands to involve the reunion of the rational soul with matter after a period of separation at death. Aquinas believes that he has philosophical as well as theological reasons to advocate this doctrine; as we'll see, his general theory of human nature leads him to posit a bodily resurrection as opposed to the continued existence of disembodied souls in the afterlife.

Indeed, Aquinas presents several arguments in SCG, IV.79 in defence of the claim that ‘the resurrection of bodies will come through Christ’,Footnote ¹¹ all of which rely on the further belief that it goes against the human soul's very nature to exist apart from matter.Footnote ¹² In his first philosophical argument in chapter 79 in support of the bodily resurrection, for example, Aquinas appeals to the need the soul has for union with the body:

Aquinas's argument here in favour of a bodily resurrection relies on two claims familiar from his general account of human nature, namely that: (1) the soul is, by nature, immortal, and that (2) the rational soul's nature as the substantial form of the human being mandates union with a body.Footnote ¹⁴ The explanation for (2) is that – since the very ‘essence’ of the rational soul involves structuring, organizing, and vivifying a human body – a soul separated from a body can't do what it's meant by nature to do. Although the soul's nature doesn't require being joined to the body at all times, it is unnatural (in the strict sense of ‘natural’) for it to be separated from matter, and Aquinas's point here is that this state of affairs can't continue without end. Since the human soul is immortal, however, it would remain in that unnatural state perpetually unless it were reunited with matter, and so it's clear (if we accept the premises of the argument) that the soul must be joined to a body again at some point.

The main interest of this particular argument lies in its application of the general principles of Aquinas's theory of human nature to the special case of the bodily resurrection. We might well expect Aquinas to shy away from discussing his claim (stated explicitly in Summa Theologiae, Ia.75.4) that a human soul is not identical with the human being, and that the soul is ‘incomplete’ in separation from the body. After all, it's this very emphasis on the composite nature of the human being that appears to cause serious problems for his account of post-mortem human identity. Instead, Aquinas uses exactly that point to support the doctrine of the bodily resurrection.

In the following argument of SCG, IV.79, Aquinas stresses this point even more strongly, underscoring the soul's status as part of the composite human being rather than the whole human being: ‘The soul separated from the body is in a way imperfect, like every part existing apart from its whole: for the soul is naturally part of human nature.’Footnote ¹⁵ What's more, Aquinas goes on to argue that a perpetual separation of soul from body would mean that complete happiness could never be achieved: complete happiness involves the satisfaction of all natural desires, and the separated soul naturally inclines toward reunion with its body (in the same way that a dropped rock falls downward because of its natural inclination to be ‘down’). Human nature requires that a human being possess both body and soul; as Aquinas states in his commentary on Peter Lombard's Sentences, ‘The soul of Abraham is not Abraham himself, properly speaking, but is part of him’ (43.1.1a.ad2).Footnote ¹⁶ Later, he adds, ‘Other things being equal, the status of the soul in the body is more perfect than the status of the soul outside the body, since it is part of the whole composite’ (ibid., ad4).Footnote ¹⁷ If the rational soul existed perpetually apart from the body, one part of the human being – David's soul – would persist, while the whole human being – David himself – would be lost.

It seems clear, then, that Aquinas believes not only that a bodily resurrection is compatible with his account of human nature but that it is in fact demanded by it for the immortality of an individual human being. At the same time, Aquinas recognizes that, on his account, the bodily resurrection raises vexing questions about human identity – questions he attempts to answer in SCG, IV.81. In what follows, I focus on one particularly pressing objection to the claim that the very same human being is present after the resurrection as existed before death and examine Aquinas's response in light of a criticism raised to the objection by Christopher Hughes.

The principle of non-repeatability and Hughes's criticism

In SCG, IV.80, Aquinas lays out three objections to the view that the resurrected human being will be numerically identical with the original human being. The most philosophically daunting proceeds as follows:

This argument crucially depends on what I'll call the principle of non-repeatability: viz. the principle that no thing A that is destroyed (i.e. corrupted) at time t can be numerically identical with a thing B that exists at a later time t′. This claim is supposed to be analogous to Aristotle's point in Physics, V.5 that a disposition (such as health) that is acquired after a privation (in this case, sickness) is numerically distinct from the original disposition.Footnote ¹⁹ In other words, the health David possesses before he gets a cold is numerically distinct from the health David possesses after he recovers. Once David's original health has been corrupted by disease, it can't be restored as the very same disposition – David has a different instance of ‘health’ before and after his sickness.Footnote ²⁰

According to this objection, what's true in the case of dispositions is also true in the case of natural things. For example, if, after an oak tree A is cut down and used for firewood, an oak tree B grows in exactly the same place, it seems clear that A and B are numerically distinct, even if they happen to be qualitatively identical. In fact, on this line of argument, the non-repeatable nature of natural things is the very reason why species reproduce: the process of generation of individuals within a species is what ensures that the species will continue despite the corruption of its individual members. Individual oak trees are non-repeatable, and so they produce acorns in order for there to be other oak trees after the original ones die. More to the point, according to this general principle of non-repeatability, once a human being dies and is corrupted, it is impossible for a human being to exist at a later time who is numerically identical with the original human being. (That the human being is corrupted seems evident, since on Aquinas's theory a human being is a composite of soul and body.) Once David dies, this objection claims, we've lost David forever, even if God produces something which looks and acts exactly like David.

The principle of non-repeatability (PNR) seems obviously true in the cases I've discussed: in the normal course of nature, you don't get the same members of a natural species repeated after they die – you get new members of the same species. In his response to this objection, Aquinas himself accepts PNR without discussion. Yet, as Christopher Hughes has argued in a discussion of this passage, PNR seems obviously false in other cases; thus Hughes claims that Aquinas should have responded to this objection by rejecting the principle out of hand.Footnote ²¹

Hughes makes this point by first summarizing objection one as follows: ‘Once things have undergone corruption, they cannot come back into existence. At death a man undergoes corruption; so he cannot come back to life’ (98); Hughes then derives a ‘principle of continuity’ based on this, namely, C1: Necessarily, in the course of nature: if a and b are identical, and if a exists at time t, and b exists at time t′, then a is not corrupted between t and t′ (99). Hughes then claims, first, that Aquinas accepts C1 and, second, that he's wrong in doing so.

In order to prove that Aquinas should have denied C1, Hughes constructs a thought-experiment involving two qualitatively identical bicycles, A and B. Suppose, he says, he brings the bikes home from the shop and completely disassembles them. He then puts half of A's parts together with half of B's parts, and half of B's parts together with half of A's parts. Now there appear to be two new bicycles, call them C and D, which are identical neither to each other nor to A and B. At this point, however, he can disassemble those bicycles and put all the parts that were originally in A back together, and all the parts that were originally in B back together, ‘so that’ he says, ‘everything looks just as it did when I brought the bicycles home from the shop’ (107). At this point, it appears that A and B have come back into existence, and that C and D have ceased to exist. Of course, he could go through the process of disassembly and reassembly again, at which point C and D will come back from nonexistence. ‘So’, Hughes concludes, ‘both (C1), and the stronger principle that results from deleting ‘in the course of nature’ from (C1), appear not to be true’ (107).

In fact, it doesn't even seem necessary to go to such extravagant lengths in order to find examples that appear to refute both C1 and PNR. Take the simple case of a broken lawnmower that is disassembled, repaired, and then reassembled. What we seem to have here is one, not two, numerically distinct lawnmowers, despite the fact that the lawnmower is ‘corrupted’ when its parts are strewn across my driveway. Given this rather common happening (in cases involving, e.g. lawnmowers, bikes, watches, and computers), Hughes seems right in arguing that it does seem possible for things to be first corrupted and then repeated with numerical identity.

Hughes is also right in thinking that Aquinas doesn't appear to recognize this difficulty with PNR, and not for lack of similar objects or similar examples in his own lifetime. (In the section of his Sentences commentary devoted to the bodily resurrection, for example, Aquinas's contemporary, Bonaventure, considers whether a wooden chest that is taken apart and then reassembled is numerically identical with the original wooden chest.Footnote ²²) In his reply to this objection, Aquinas accepts the principle of non-repeatability as given and works at providing an argument for why the case of resurrected human beings can be an exception to it. In so doing, Hughes argues, Aquinas gives himself needless trouble.

Artefacts and natural things

In making this argument, however, I believe that Hughes himself overlooks a crucial qualification that is built right into the original statement of PNR in SCG, IV.81; as a result, neither Hughes's summary nor his proposed principle of continuity adequately captures the force of the original objection. In fact, I'll argue that Aquinas is right in accepting PNR, and that this objection proves harder to overcome than Hughes believes – although Aquinas's account does possess the resources with which to do so.

Recall that the objection as stated in IV.81 began with the claim that ‘in no natural thing [naturalium rerum] is that which is corrupted found to be brought back to existence the same in number.’ Hughes glosses this in his principle of continuity as the claim that ‘Necessarily, in the course of nature: if a and b are identical, and if a exists at time t, and b exists at time t′, then a is not corrupted between t and t′’ (99, added emphasis). In Hughes's summary, then, the principle of non-repeatability becomes the general claim that, in the natural world, no thing that is corrupted can come back into existence.

I believe, however, that the original mention of natural things isn't just a casual reference to the normal state of affairs. Rather, the objection is very carefully intended to pick up on the distinction between natural things and artefacts. That is, the principle on which the objection rests (and to which Aquinas responds) is a principle pertaining specifically to the non-repeatability of natural things, not to all things found in the physical world. Thus, although Hughes is right that PNR fails for artefacts like bicycles and lawnmowers, that failure doesn't impact the original objection: the principle was never meant to apply to such cases anyway. And, as we'll see, it's not at all obvious that PNR fails in the case of natural things.

Although Aquinas doesn't explicitly mention artefacts in SCG, IV.81, he distinguishes between natural substances and artefacts in numerous places, including three of his earlier discussions of the bodily resurrection (namely, Scriptum, IV.44.1.1b.ad4, 1c.sc1, and Quaestiones Quodlibetales, 11.6.1.ad3).Footnote ²³ In each of these passages, Aquinas draws a sharp distinction between natural things and artefacts, arguing that they have different identity conditions.

In fact, in QQ, 11.6.1, Aquinas brings in the distinction between natural things and artefacts precisely when addressing the identity of the resurrected human body. The discussion here arises in response to the objection that the resurrected body cannot be one in number with the original body. For, as ‘the Philosopher says in his book On the Soul, the statue which is destroyed is not the same as the statue which is re-fashioned from the same gold. By the same argument, the body which is now corrupted will not be numerically identical with the body which is resurrected.’Footnote ²⁴ That is, if I take a gold statue of Hypatia, melt it down, and refashion it into another statue of Hypatia, it seems fairly clear that there are two, numerically distinct statues involved even if the two statues resemble each other exactly.Footnote ²⁵ In the same way, the objection goes, if David's body is completely ‘melted down’ or corrupted after death, then the body that is refashioned at the end times must be numerically distinct from David's original body.

Aquinas responds to this objection by claiming that statues are different from human bodies in one very important respect: statues are artefacts, and human bodies are natural substances:

Because the forms of artefacts, such as statues (and bicycles), are accidental forms, then, they are most properly placed in a genus and species according to their matter (e.g. gold or steel), although they can also be placed in a genus and species according to the artefactual form ‘statue’ or ‘bicycle’. Natural things, on the other hand, are placed in genera and species only according to their substantial forms (which artefacts don't possess per se).

As Aquinas points out, this distinction entails that the identity conditions for artefacts differ from the identity conditions for natural substances. In particular, it means that there are two possible answers to the question ‘Is this the same statue?’, but only one possible answer to the question ‘Is this the same human being?’. In the case of the statue, the answer depends on whether you're referring to the matter (the gold), in which case the answer is ‘Yes’, or whether you're referring to the artefactual form (‘statue’), in which case, the answer is ‘No’.Footnote ²⁷ The main reason for the ambiguity is that, in the case of artefacts, the only real substance in question is what's being referred to as the matter: gold, wood, steel, etc. But gold, wood, and steel are already composites of substantial form and matter. In the case of natural substances such as human beings, of course, this problem simply doesn't arise.

Thus, it seems that Aquinas would solve the question of the identity of the reconstituted statue or the reassembled bicycles by claiming that whether or not the thing counts as the same statue or the same bicycle depends on whether you're appealing to its matter or to its artefactual form. To return to Hughes's example involving bikes A and B, Aquinas would apparently say that the reassembled bicycles can count as A and B insofar as they possess the same matter that originally constituted A and B. In the same sense that the two statues fashioned from the same gold count as the same statue (because the same gold is involved in both cases), the bicycles count as the same bicycles (because the same steel, plastic, etc. is involved in both cases).

When considered this way, however, Aquinas's account looks problematic. According to the position he's laid out, it looks as if the original bike is identical with the reassembled bike in exactly the same way that the original bike would be identical with a bicycle made up of parts which had been melted down from the original bike and refashioned so that what used to be the fender was now the handlebars, etc. Same ‘stuff’, different artificial forms. This position goes directly against our intuitions in these cases, however. I think we want to say that in the case Hughes imagines, the reassembled bicycle is identical to the original bicycle, whereas the totally reworked bicycle isn't. But it looks as if the position Aquinas adopts with respect to artefacts commits him to the highly unintuitive claim that the reassembled bicycle is identical to the original bicycle in exactly the same, very weak sense that the completely refashioned bicycle is identical to the original – that is, the sense in which both bicycles are made from the same ‘stuff’. Fortunately, the real issue at hand isn't whether Aquinas has picked out the right criteria of identity for artefacts, but whether the distinction he draws between artefacts and natural things defends the principle of non-repeatability against Hughes's objection. The bicycles count as numerically distinct bicycles insofar as the artefactual form ‘bicycle’ is concerned.

For our purposes, what proves most important about the distinction Aquinas draws here between artefacts and natural substances is that the original objection explicitly specified that ‘for no natural thing is that which is corrupted and that which is returned to being the same in number’. It seems clear that – in light of Aquinas's claim that artefacts and natural things possess differing identity conditions – we should thus take PNR as meant to refer only to natural substances, such as oak trees or hamsters (call this, if you want, the principle of natural non-repeatability).

This clarification about the scope of PNR has significant consequences for its plausibility, however, for none of the examples raised so far that appear to refute the principle of non-repeatability involve natural substances. Indeed, when PNR is properly understood, it becomes significantly harder to imagine counter-examples to the principle. The principle seems especially plausible in the case of living organisms, a sub-set of natural things, and the sub-set to which human beings (the natural things in question) belong. It's certainly more difficult to conceive of how a hamster which has died and decomposed could be reconstructed as the very same hamster than it is to conceive of how a bicycle which was taken apart could be restored.Footnote ²⁸ Aquinas, after all, is addressing the corruption of a human body at death, not a Frankenstein-style case in which different body parts are removed from and then reattached to living organisms: he acknowledges that the matter that constitutes a human being's body can undergo substantial fluctuation throughout the life of the human being.Footnote ²⁹

For Aquinas, the key feature which sets living organisms apart from artefacts is that living beings (and not artefacts) possess a unifying principle of life – an esse – which seems impossible to restore to an organism once it has lost it. It's precisely the difficulty of explaining how a natural thing that has ceased to live can be numerically identical to something that exists at a later time, however, on which the first objection in SCG, IV.80 focuses – not difficulties involving non-living lawnmowers and statues.

Given, then, that PNR is meant to apply only to natural substances and not to artefacts, it seems that Aquinas is faced in SCG, IV.80 with a perfectly legitimate objection (and, in fact, one which is strikingly similar to contemporary objections to the resurrection of the body): namely, how can a resurrected human being be the very same human being who ceased to exist at death? As the objection points out, ‘human beings are corrupted through death, and the body of a human being is broken down all the way to the first elements’. If human beings aren't ‘repeatable’ in the way that artefacts are, it does seem impossible for the resurrected David to be numerically identical with the original David.

Aquinas's response

Nevertheless, given both Aquinas's general theory of human nature and what he's said about the relation between body and soul only one chapter earlier in SCG, it seems clear that Aquinas has an answer to this objection ready to hand. In particular, we might expect Aquinas to respond to this objection by explaining that human beings prove an exception to the general rule because – unlike all other living organisms – they possess immortal souls that survive their death. In other words, we might expect Aquinas to counter the objection by pointing out that human beings aren't completely corrupted at death; PNR is true, but the bodily resurrection doesn't violate it because the human being never actually ceased to exist in the relevant sense.

It's initially surprising, then, that Aquinas's response doesn't focus at all on the unique status of the rational soul. Rather than concentrating on the sense in which the human being isn't corrupted at death, Aquinas focuses instead on God's ability to do things which nature can't:

The argument here, simply put, is that God can do things nature can't, including restoring life to something that had lost it. The reason for this, Aquinas states here, is that nature always has to act through forms: if a natural object has been corrupted, then there's no form left for nature to act through. Thus, something that has been corrupted can't be restored by nature. God doesn't share this limitation, however, and so He's able to restore the same thing to existence even after it's been corrupted.

At first glance, this argument seems too strong – and unnecessarily so. Aquinas's claim that ‘the divine power, which brings a thing into existence, is able to produce an effect of nature … apart from nature’, and, thus, that ‘since the divine power remains the same even when things are corrupted, it can restore the corrupted thing to integrity’, could easily be read as the claim that, since God's power remains constant, God can recreate anything which has been corrupted as the very same thing.

But this claim seems doubtful at best, and blatantly false at worst. As Peter van Inwagen argues in a famous thought-experiment, if a group of monks claims in 1997 to possess a manuscript ‘written in St Augustine's own hand’ which was burned by Arians in 457, and yet which was miraculously recreated by God in 458, we're likely to have the following reaction:

In other words, even God can't recreate a physical object once it's been completely destroyed, because the recreated object wouldn't possess the right sort of causal connection to the original. At best, God could produce a perfect duplicate of the original object. This seems as true in the case of hamsters, oak trees, and human beings as it does in the case of the manuscript. On these grounds, then, it seems doubtful that even God could resurrect a human being who is numerically identical to one who has died and whose body has decomposed, despite what Aquinas claims here.

What makes Aquinas's ‘God-can-do-things-nature-cannot’ response to the non-repeatability objection especially odd, moreover, is that it fails to appeal to the continued existence of the human substantial form – namely, the rational soul. Aquinas holds that one of the primary characteristics that distinguishes the substantial form of a human being from the substantial form of every other physical substance is that human souls survive the death of the composite, while the forms of all other material substances perish. In fact, as we have seen, Aquinas appeals to the immortality of the human soul in defending the very possibility of bodily resurrection. If the substantial form of a human being never goes out of existence, though, it would appear that both God and nature do still has something to act through; so it seems, on this argument, that the resurrection of the body should be possible through either an act of God or an act of nature. Thus, it might appear that Aquinas has not only overlooked the obvious point that human forms survive death, but that he's also overlooked an obvious consequence of this claim – viz. that the bodily resurrection is something nature can accomplish.

The resurrection of the body

I believe, however, that Aquinas is intentional in his not bringing the separated soul into his response to this objection, for I believe that the primary concern in both the objection and the reply is the status of the corrupted human body and only consequentially the status of the composite human being. The original objection focuses on the fact that ‘the body of a human being is itself broken down all the way to the first elements’; in his response, Aquinas picks up on this worry, claiming that ‘although this can't be brought about by nature – namely, that a corrupted body be restored to life – nevertheless, this can be brought about by divine power’. Human bodies, after all, don't differ from the bodies of other living organisms in terms of their decomposition after death.

With this focus, Aquinas's claim that nature doesn't have a form to work with in the case of human death seems more plausible. When the body is corrupted, it does lose the form that used to be its principle of action: the human soul persists apart from the body and outside the realm of nature. That's just what it means for a human being to be dead – the rational soul separates from matter and persists in a disembodied state until the bodily resurrection. Although the rational soul survives the death of the composite human being, then, it's not available to nature qua form. Thus, nature can't act through the form of the human being in order to restore the human body to life.

This also makes Aquinas's claim that in this case God can do something nature can't do seem more relevant. Although the human soul is not available to the natural realm, God still has ‘access’ to the human soul and can restore the human body by rejoining the body to its principle of action. If we restrict the scope of Aquinas's claim about divine power only to the cases in which a form survives the death of the composite – i.e. only to the case of human beings – it seems that Aquinas does have some reason for claiming that, although human beings can't be brought back to life through the normal course of nature, God can act above and beyond nature to reunite the still-existing human soul with matter; this act will result in the restoration of both that human being, and that human being's body.

Furthermore, even if Aquinas's claim is taken as applying broadly to all natural substances (and not just to human beings – the only natural substances whose substantial form survives death of the composite), at least some people believe that God can recreate a physical organism which has been completely destroyed. Here again, the distinction between natural substances and artefacts becomes relevant, since artefacts (such as manuscripts) appear to require a certain sort of origin to count as the same artefact. Lynne Rudder Baker, for instance, argues that Van Inwagen's analogy of the burnt manuscript fails in one crucial respect to parallel the case of living organisms, particularly human beings:

That is, Baker argues, if God is able to create a resurrected body at all, it seems plausible to suppose that God could guarantee that such a body constitutes a particular person. If we suppose that God could recreate a physical body numerically identical to David's original body, then it seems that Aquinas would be right to claim that God is able to recreate any physical organism at all. On such a position, even the overstated version of Aquinas's response would effectively counter the original objection.Footnote ³³

Causal connections and ‘gappy’ existence

Aquinas's focus on the corrupted human body (rather than on the rational soul) thus renders his reply more philosophically plausible than it first appears. It doesn't, however, seem adequate to explain how the identity of the resurrected to the original David is compatible with the radical break in continuity that death appears to constitute. Although Aquinas's reply to the objection is incomplete in this way, I believe that Aquinas's general account of human nature does possess the resources with which to respond to this worry. In the remainder of this paper, I sketch what such a response might look like by: (1) appealing to the importance of immanent causal connections in identity, and then (2) arguing that the persistence of the rational soul is sufficient to guarantee that the resurrected human being bears the appropriate causal relation to the original human being.Footnote ³⁴

As we've seen, Aquinas's claim that a human being is identical to the composite of matter and substantial form entails that a human being ceases to exist at death and prior to the bodily resurrection. Both defenders and critics of Aquinas have long identified this difficulty – what I'll call the problem of ‘gappy’ existence – as one of the most serious difficulties facing his account of human identity.Footnote ³⁵ Sandra Edwards argues that Aquinas is, in fact, unable to answer this worry adequately:

This is not a problem unique to Aquinas's account of human identity, however: gappy existence poses a problem for any non-substance-dualist account of personal identity (including materialist accounts) that attempts to accommodate the bodily resurrection without claiming that the body somehow survives our death (due to, e.g. last-minute fission or God's miraculous intervention). In general, any theory which holds that a person is not identical to her soul (and which also holds that there will be a bodily resurrection) will need to address the problem that – for all appearances – that person ceases to exist for a time at death.

Some people try to solve this problem by claiming that death constitutes the end of our existence as temporal creatures, and, thus, that there is no temporal gap in existence between death and the bodily resurrection. Brown, for instance, tries to solve the problem of ‘gappy’ existence as follows: ‘Discontinuity depends on a break in time, and … time is not at issue here’ (193–194). This doesn't seem like a promising solution to me, at least with respect to Aquinas's account of human nature, for at least two reasons: (1) as we'll see, the real problem with the bodily resurrection doesn't seem to be a gap in time but rather a gap in causal connections; and (2) Aquinas is far more concerned with explaining human identity that he would need to be if he adopted Brown's line on the separated soul. Brown's defence of this position also rests on the supposition that separated souls exist in aeviternity, like the angels; there appears to be no textual support for this claim in Aquinas, however, and it would pose a variety of other problems for Aquinas's account of the bodily resurrection (since material beings necessarily exist in time).

For this reason, the growing consensus that temporal gaps in a person's existence don't necessarily pose a serious impediment to continued identity represents a particularly interesting development in contemporary philosophy. Spatio-temporal continuity is increasingly seen as neither a necessary nor a sufficient condition for something's persisting as the same object.Footnote ³⁷ Thus, many contemporary philosophers (whose intuitions are primed with heavy doses of Star Trek malfunctioning-transporter examples and defective brain-state transfer devices) don't see spatio-temporal gaps in existence as, in and of themselves, constituting an insurmountable difficulty for accounts of personal identity. Instead, such philosophers claim that the real challenge is providing an account of personal identity which guarantees the correct sort of causal connections between the person at time t and the person at time t′. Although Captain Kirk may not actually exist between time t and time t′ (when the transporter he was using malfunctioned and failed to transport him instantaneously), there's a growing intuition that the Captain Kirk who's finally transported to the Enterprise at time t′ is numerically identical to the Captain Kirk who entered the transporter at time t, so long as the right causal connections obtain.

What this means for philosophical defences of the bodily resurrection, of course, is that the problem of explaining how the resurrected David is identical to the original David isn't a problem posed first and foremost by a temporal gap in his existence, for a temporal gap will pose an indefeasible difficulty only if it is accompanied by a gap in the relevant sorts of causal connections. If the problem facing a philosophical defence of bodily resurrection involves preserving appropriate causal connections between the earthly and resurrected human being, however, then the real challenge for Aquinas is to provide an account of human identity that can explain how these sorts of causal connections are preserved between the resurrected and the original human being. And this is just what I think his account does provide, with its emphasis on the rational soul – that which makes a human being that which it is, and which continues at death – as grounding human identity.

To see this, it's helpful to look more closely at the role of immanent causation in diachronic identity. First, although it's difficult to pin down exactly what causal relations are ‘appropriate’, it seems true that in order for a material object to count as the same thing over time, its later states must be causally dependent on its earlier states in some way. As Dean Zimmerman says,

To preserve identity, moreover, the appropriate sort of causal dependence must obtain. In particular, although God's action of recreating a human being at the bodily resurrection can be seen as ensuring some sort of causal dependence of the post-resurrection body on the earlier body (assuming that God fashions the resurrected David from a sort of ‘blueprint’ of the original David), it doesn't seem to be enough to guarantee diachronic identity:

In particular, God's using a mere mental blueprint of David-at-death in recreating David at the bodily resurrection doesn't appear to preserve the immanent causal connections which need to obtain between David's different temporal stages. God's act of recreating David in this way would appear instead to constitute the beginning of a new life, in the same way that (as we have seen) his creating in 458 a perfect duplicate of the manuscript burned in 457 constitutes the beginning a new manuscript and not the continuation of the old one. A life is the sort of thing whose ‘causal paths’ end at death; God can't recreate a being numerically identical to the original David if David's life has ended. It seems, then, that the resurrected human being can be identical to the original human being only if, in some way or other, the life of a human being doesn't end at death – that is, if the appropriate causal paths remain intact.Footnote ³⁹

It is no small matter, then, that Aquinas's general account of human nature leaves him in the position to make exactly this claim. According to Aquinas, a human being's life, understood as her esse (‘being’, or ‘actualized existence’), doesn't end at death.Footnote ⁴⁰ Rather, it continues in virtue of the soul's persistence. In his words:

Although David doesn't exist as such when his soul is separated from matter, then, the resurrected David doesn't have two beginnings of existence, properly speaking, because his life – his esse – continues via his soul at his death.

One might worry here that claiming that David doesn't exist, properly speaking, while his existence continues is – at best – a contradiction in terms. Yet this is precisely Aquinas's view, and its plausibility rests entirely on the sense in which the rational soul differs from both all physical objects and the substantial forms of all other physical substances. Although it is true on Aquinas's account that, were you to remove David's foot from the rest of his body, David's foot would possess a new ‘esse’ (since it's no longer ‘David's foot’ but now ‘detached foot’), the same is not true in the case of the separated soul. Because the soul can (and does) persist in separation from matter – unlike all other substantial forms – Aquinas claims that it preserves David's original esse. As he claims in the above passage, because the soul can persist apart from matter, its esse, ‘which was [the esse] of the composite, remains in the soul after the dissolution of the body; and when the body is restored in the resurrection, it is brought back in the same esse – the esse which remains in the soul’. In short, the soul's continuing to exist proves sufficient for David's esse to continue to exist.

Once we grant Aquinas the existence of this separated soul, I believe that we can make sense of his claims about the rational soul's grounding the identity of the human being (without being identical to the human being) in terms of its guaranteeing the proper sorts of immanent causal relations.Footnote ⁴² It seems to me that, on Aquinas's account of human nature, the persistence of the rational soul – the substantial form of the human body – at death can be seen as meeting Zimmerman's reasonable requirement of ‘preserving the self-sustaining structure peculiar to the living thing in question’, even in separation from matter. During earthly life, the persistence of the human soul guarantees the preservation of such a structure peculiar to the living human being, and there's no reason why, if the soul persists at death, it should be thought of as losing its ability to preserve that structure after the human being's death simply because that ability is not being actualized.Footnote ⁴³

On Aquinas's theory, then, the very nature of the human soul guarantees that the causal connections between the earlier stages of David's earthly existence to the later stages of his resurrected existence are of the ‘right sort’. For the appropriate immanent causal relations to obtain, David's resurrected body needs to be the way it is primarily because of the way his body was at death, and this is precisely what holds true on Aquinas's account. David's body was the way it was at death primarily because of David's structuring, vivifying, life-preserving soul, and David's resurrected body is the way it is primarily because of that same soul, whose existence continues uninterrupted throughout earthly life, death, and the bodily resurrection. In this way, David's resurrected existence as David – instead of being explained directly in terms of God's creative actions – can be explained in terms of immanent causal connections obtaining between his earlier and later temporal stages. Thus, it seems that the continued existence of the rational soul is sufficient to preserve the necessary causal connections between the resurrected and the original David, despite the temporal gap in David's physical existence after death and prior to the resurrection of the body.Footnote ⁴⁴

Moreover, Aquinas's account builds the preservation of our identity into the very centre of his theory of human nature. God's only role in the bodily resurrection in this theory is to reunite our forms with matter. Since human beings are by nature composites of form and matter (the substantial form of David makes him what he is: a living, breathing human being, while his form's unique relation to his body distinguishes him from all other human beings), God's role in the bodily resurrection can be seen as the act of putting right what was put wrong by death: that is, rejoining what's meant by nature to be together – form and matter. In this way, Aquinas's account has an edge on contemporary accounts that require God's dramatic intervention at the moment of death, ‘snatching’ our bodies or central nervous systems at the moment of death and replacing them with simulacra, or ‘fissing’ all of our cells at the moment of death.Footnote ⁴⁵

To sum up, on Aquinas's account of human nature, David's identity over time is generally ensured by the persistence of his substantial form in union with some matter or other. At death, however, David's soul persists in separation until it's joined again with matter at the bodily resurrection. Although David doesn't exist, properly speaking, during this period of separation, the persistence of his soul is sufficient to guarantee the persistence of the appropriate sorts of immanent causal relations between David's temporal stages, and so the resurrected David is causally related to the original David in a way sufficient for him to count as the same human being. Furthermore, the rejoining of David's soul with matter results in the recreation of David's own body, since David's body just is the physical organism resulting from the union of his substantial form with matter.

In conclusion, although not without its problems, Aquinas's account of human nature yields an account of the bodily resurrection that proves not only highly interesting but also at least as (if not more) plausible than many modern accounts. I believe that philosophers and theologians alike should agree that his theory deserves attention not just for its historical importance but for its continued relevance to contemporary discussions.Footnote ⁴⁶