1. Introduction: Did Aquinas change his mind?Footnote ¹

There seems to be no consensus among scholars about whether Aquinas changed his view on the perfection of the separated soul’s natural cognition, i.e., the cognition of the separated soul by its natural power alone.Footnote ² Anton Pegis argues that Aquinas changed his view. According to Pegis, Aquinas in his earlier stage (InSent IV, d.50, q. 1, a. 3; DV, q. 19, most notably SCG II, c.81, and, for Pegis, Quod. III, q .9) held the ‘pre-Aristotelian’ view,Footnote ³ which says that a separated soul will ‘function perfectly as a separate substance’.Footnote ⁴ In Aquinas’s later stage (QDA q. 15–20 and ST I, q. 89), however, he rejects this ‘pre-Aristotelian’ view,Footnote ⁵ holding rather that a separated soul ‘does not have the intellectual power to function properly as a separate substance’.Footnote ⁶ Simply put, Pegis argues that the mature Aquinas downgraded the perfection of the separated soul’s natural cognition.

However, unimpressed by Pegis’s argument, John Wippel insists that ‘I do not find a radical break or downgrading of the knowledge Thomas attributes to the separated soul in SCG II, c.81 and his earlier treatments, on the one hand, and ST I, q. 89 and QDA q. 15–20, on the other, nor do I find his various treatments of this topic fundamentally inconsistent with one another’.Footnote ⁷ Why not? Wippel’s reasons can be briefly summarized as follows. First, SCG II, c. 81 states that a separated soul ‘will be perfectly like separated substances as regards its mode of understanding’.Footnote ⁸ This does not contradict Aquinas’s position in ST I, q. 89, a. 1, since Aquinas affirms that separated souls will have a higher mode of understanding in both texts. Second, even Pegis himself notices that his reading of SCG II, c. 81 is in severe tension with Aquinas’s claim in SCG IV, c. 79, that separation from the body is against the nature of the human soul.Footnote ⁹ Third, Wippel detects no radical breaks or inconsistencies in his survey of a wide range of texts (InSent III, d. 31, q. 2, a. 4; InSent IV, d. 50, q. 1, a. 3; DV q. 19, a.1–2, and SCG II, c.80–81, ST I, q. 89 and QDA q. 15–20) with respect to five questions.Footnote ¹⁰ While more can be said on behalf of both Pegis and Wippel, the upshot is that they disagree on whether Aquinas downgraded the perfection of the separated soul’s natural cognition. Pegis says yes, but Wippel says no.

In this paper, my intention is not to evaluate the debate between Pegis and Wippel in further detail. Instead, I aim to advance the debate by considering Aquinas’s position on the issue in InSent IV(1252–56) d. 49, q. 1, a. 4, qc1. To my knowledge, this text has not been discussed in relation to this issue in any scholarly work. I contend that Aquinas’s position in this InSent text is incompatible with his position in ST (1265–68) I, q. 89, a. 1.

I do not aim to conclusively establish that Aquinas changed his view, nor do I aim to generalize the two positions to other texts of Aquinas, both of which would require a detailed and comprehensive survey of many other texts, including but not limited to those Pegis and Wippel surveyed. In this paper, I will confine myself to interpreting the two texts, unpacking their positions, showing how these two positions are grounded on two markedly different views on how the human body perfects the human soul, and eventually identifying the incompatibility between the two positions. The incompatibility, I argue, enhances the plausibility that Aquinas changed his view on the issue.Footnote ¹¹

I will proceed as follows: In section II, I will first clarify Aquinas’s position in ST I, q. 89, a. 1, co. Then, based on Aquinas’s position in the ST text, I will formulate a strategy for reconciling apparent inconsistencies between Aquinas’s position in ST I, q. 89, a. 1 and in other texts. After that, in section III, I will discuss the InSent IV d. 49, q. 1, a. 4, qc1 and explain why the position therein is incompatible with that of ST I, q. 89, a. 1.

2. ST I, q. 89, a. 1, co

In ST I, q. 89, a. 1, co.,Footnote ¹² Aquinas argues that a separated soul can understand. Yet, since the human soul-body union is not in vain, the body should somehow improve the soul’s understanding, so a separated soul’s understanding should be less perfect than that of the embodied soul.

Aquinas begins by pointing out that the difficulty for holding that separated souls can naturally cognize lies in the centrality of phantasms to the human embodied mode of understanding, i.e., the human soul turns to phantasms to understand the essence of material things.Footnote ¹³ Then, Aquinas mentions an alternative view he considers Platonic, according to which the embodied soul turns to the phantasms just because the soul at the embodied stage ties accidentally to and is impeded by the body. Once the soul is free from the body, it will cognize according to its nature like a separate substance, i.e., without needing phantasms to understand.Footnote ¹⁴

Aquinas then immediately rejects this Platonic alternative by appealing to the soul-body union. He says,

For Aquinas, the human body and the human soul are related as matter and form,Footnote ¹⁶ and the soul-body union requires that the body is for the soul’s betterment since ‘matter exists for the sake of the form’. Aquinas argues that the Platonic view fails because it implies that the soul-body union makes the body better but the soul worse. Thus, given the Platonic view, the body (matter) does not exist for the sake of the soul (form).

Aquinas’s rejection of the Platonic view based on the human soul-body union here is continuous with his discussion in ST I, q. 84, a. 4, co., where Aquinas rejects the Platonic and Avicennian view that when embodied, human intellect understands by directly receiving an infusion from separated forms without the mediation of senses. The detail of the Platonic and Avicennian view aside, Aquinas’s most relevant point in q. 84, a. 4 for us is that since the body exists for the soul, the body should be for the being or proper operation of the soul. However, since the (human) soul’s being does not need the body, the body should be for the soul’s understanding.Footnote ¹⁷ In ST I, q. 89, a. 1, co., Aquinas uses the same reason, i.e., the body is for the soul’s understanding, to reject the Platonic view on the separated soul’s cognition. In this text, Aquinas continues reflecting on the implication of the human soul-body union that he had already begun in ST I, q. 84, a. 4. co.

Now, let us continue reading ST I, q. 89, a. 1, co. Aquinas’s rejection of the Platonic view actually constitutes part of the problem to be addressed, namely, the problem concerning how it is possible to reconcile the separated soul’s natural cognition with the human soul-body union that is not in vain.Footnote ¹⁸ Aquinas holds the following two claims: (i) the human soul, by nature, needs phantasms to understand when embodied and (ii) the human soul-body union is not in vain. As already mentioned, the Platonic view clashes with (ii). Thus, (ii) rules out the Platonic view. After dismissing the Platonic view, the only option left to Aquinas, apparently, is that the separated soul cannot understand. This is because, given that the soul’s nature does not change when separated, it seems that, with the same nature, the soul will still need phantasms to understand when separated from the body. However, a separated soul has no body and no phantasms. Thus, it seems that (i) leaves Aquinas no choice but to deny that the separated soul can understand. Yet, Aquinas cannot deny it. As Aquinas says in ST I, q. 89, a. 1, sc., the possibility for a separated soul to exist implies that it has its proper operation: understanding.Footnote ¹⁹ Thus, Aquinas has to look for logical room to affirm that the separated soul can understand in a way consistent with (i) and (ii).

The first step Aquinas takes to address this problem is to clarify that (i) is compatible with separated souls having natural cognition. This is because the soul’s mode of operation follows from the soul’s mode of being. The human soul should have different modes of operation corresponding to the soul’s embodied and separated mode of being. Therefore, (i) does not rule out the possibility of a separated soul having a mode of understanding that does not need phantasms.Footnote ²⁰

The problem, however, is not resolved here. Aquinas needs to consider how his account of the separated soul’s natural cognition can take (ii), i.e., the human soul-body union, into account. Before we see Aquinas’s solution, we should first consider how Aquinas articulates the following ‘doubt’:

‘[T]his reply’ refers to Aquinas’s view that the separated soul can naturally cognize without phantasms. The ‘doubt’ can be formulated as the following argument:

Therefore,

C. The human soul-body union is in vain.

This ‘doubt’ can be understood as a restatement of the objection against the Platonic view based on the soul-body union: as long as separated souls can naturally cognize without senses, they cognize by turning to the intelligible things from whom they receive intelligible species, i.e., forms by which the intellect understand. This mode of understanding seems superior to the embodied mode, as P2 affirms. The reason for its seeming superiority is not hard to imagine. One plausible reason is that this mode of understanding makes separated souls understand in the way angels do.Footnote ²² Furthermore, Aquinas holds that there is nothing in vain in nature;Footnote ²³ so if his view implies that the human soul-body union is in vain because separated souls will understand in a superior way, it also implies that such union should not exist in nature. But then it seems that Aquinas’s ‘reply’ shares the same problem with the Platonic view: separated souls have a more perfect natural cognition, so the soul-body union is in vain.

Aquinas continues and responds to the doubt as follows,

This passage shows that Aquinas’s response is to reject P3, i.e.,

Aquinas denies that P3’s consequent follows from P1 and P2. As Aquinas says in the quote, ‘[the angelic mode] of understanding was less perfect as a possibility for the soul’. Aquinas is saying that an absolutely speaking ‘better’ mode of understanding is not necessarily a better mode for the human soul. The better mode for the soul could be, absolutely speaking, the lesser mode. In that case, the body can still be for the betterment of the soul since the body makes available the mode of understanding better for the soul. Thus, the ‘doubt’ is not a sound argument for Aquinas.

Aquinas appeals to the weakness of the human soul to explain how an absolutely speaking better mode of understanding may not be a better mode for the human soul. He says,

What Aquinas says here can be illustrated by his well-known principle that whatever is received is received according to the mode of the receiver.Footnote ²⁶ Given this principle, even if an angel and a separated soul receive the same intelligible form, their resultant cognition need not be equally perfect. For Aquinas, even in our ordinary experience, two intellects receiving the same form may attain cognition with different degrees of perfection: when the same knowledge is taught to two persons, the smarter one understands better.Footnote ²⁷ Thus, for Aquinas, the fact that a separated soul shares the same mode of understanding with angels does not entail that the perfection of the separated soul’s understanding is comparable to that of the angels. Rather, the separated soul’s understanding could be much worse than that of the angels due to the weakness of the separated soul’s intellect. In that case, the possibility that an embodied intellect may have a more perfect natural cognition becomes less implausible. In fact, Aquinas says further that, unlike the embodied intellect’s cognition, the separated soul’s cognition of material things will be ‘general and indistinct’.

Thus, Aquinas accounts for the soul-body union by pointing out that an absolutely speaking better mode of understanding may not be a more suitable mode for the human soul. Consequently, the separated soul’s understanding with an absolutely speaking better mode may lead to an overall less perfect cognition of things. As Aquinas says,

For Aquinas, this is not a mere possibility but rather how things must be given that the human soul-body union cannot be in vain. The human soul needs to unite with the body to attain an overall more perfect cognition.

To sum up, for the sake of the subsequent discussion, I would summarize Aquinas’s position in ST I, q. 89, a.1, co. as follows:

Aquinas clearly says that separated souls will have a higher, angelic mode of understanding, so his position includes (M)(a). (M)(b) is not what Aquinas explicitly says, but what Aquinas says entails it since Aquinas says that only embodied souls can attain the ‘perfect cognition’, but separated souls’ cognition will be ‘general and indistinct’ and hence overall less perfect. With Aquinas’s position in ST I, q. 89, a. 1 stated as (M), what it takes for a doctrine to contradict it is also clear: it denies either (M)(a) or (M)(b).

Before moving on to InSent IV d. 49, q. 1, a. 4, qc. 1, I would point out that (M) makes a reconciling strategy available for Aquinas interpreters to deal with texts allegedly incompatible with (M). To see the strategy, consider the following claim,

(S) Separation from the body makes the soul’s cognition more perfect.

With (M) in mind, we should see that the phrase ‘more perfect’ in (S) is ambiguous since the phrase could mean either (i) more perfect mode or (ii) more perfect overall. Thus, (S) could mean either

(Si) Separation from the body grants the soul a more perfect mode of understanding; or

(Sii) Separation from the body enables an overall more perfect cognition for the soul.

The strategy is precisely to appeal to the aforementioned ambiguity to avoid the alleged incompatibility when encountering an (S)-claim, i.e., a claim whose meaning is equivalent to (S). Since only (Sii) is incompatible with (M), an interpreter of Aquinas can utilize the aforementioned ambiguity to reconcile the alleged (S)-claims in Aquinas by arguing that the (S)-claim in question could be read to mean (Si), and hence the claim need not be read as incompatible with (M).Footnote ²⁸

To illustrate how the strategy works, we may reconsider Pegis’s argument as an example. Recall that, for Pegis, Aquinas affirms in SCG II, c. 81 that a separated soul will ‘function perfectly as a separated substance’Footnote ²⁹ but affirms in ST I, q. 89, a. 1 that a separated soul ‘could be no more than an inadequate separated substance’.Footnote ³⁰ Pegis argues that Aquinas makes an (S)-claim in SCG II, c. 81 that is incompatible with (M). To see whether Pegis’s argument works, we should consider whether the claim in SCG II, c. 81 should be read as (Si) or (Sii). As we now know, what Aquinas clearly says in SCG II, c. 81 is that the separated soul will be perfectly assimilated to separated substances with respect to the mode of understanding.Footnote ³¹ Thus, it should be read as (Si) and is perfectly compatible with (M). For this reason, SCG II, c. 81 does not show a radical break.

With this reconciling strategy in mind, we can now move on to the InSent text.

3. InSent IV (1252–56) d. 49, q. 1, a. 4, qc1

My goal in this section is to argue that Aquinas’s position in this InSent IV text is incompatible with (M). The relevant part of the text is as follows,

This text is not primarily about the separated soul’s natural cognition. Rather, Aquinas’s main point here is to argue that the saints will have a more intense beatific vision after their souls unite with the glorified body.Footnote ³³ This point about the beatific vision need not detain us. Instead, I intend to highlight Aquinas’s markedly different positions on the human soul-body (the perishable body specifically) union and the perfection of the separated soul’s natural cognition in this text. I will unpack this position before I argue for its incompatibility with Aquinas’s position in ST I, q. 89, a. 1.

In this InSent text, Aquinas states that the human soul-body relation can be considered in two ways. I would start with the second way, which is more relevant to the perfection of the separated soul’s cognition. As Aquinas says, the body ‘impedes the perfection of the soul’, because something in the body ‘resists the soul in the soul’s activities, as long as the body is not perfectly perfected by the soul’. For Aquinas, the perishable body is not ‘perfectly perfected’ like the glorified body and somehow resists the soul’s activities.Footnote ³⁴ What ‘activities’ are Aquinas talking about? Since this text is mainly about the beatific vision, which Aquinas argues is an act of the intellect,Footnote ³⁵ the context should make it clear that the activities are, first and foremost, acts of understanding. Thus, the second way clearly means that the body is, somehow, detrimental to the soul’s understanding, such that ‘the soul separated from the corruptible body can act more perfectly than when it is united to it’.

I have not yet argued that this second way is incompatible with Aquinas’s position in ST I, q. 89, a. 1. I will come back to that later. For now, I would like to consider a question related to the first way of the soul-body relation: would the Aquinas in this text hold that the human soul-body union is in vain? In ST I, q. 89, a. 1, Aquinas argues that the human soul-body union requires that the body perfects the soul’s understanding. Aquinas makes no such claim in the InSent text. Would Aquinas in the InSent text consider the human soul-body union in vain? In my view, not necessarily. In fact, Aquinas says in the text that ‘the union of body to soul adds a perfection to the soul’ because the soul is imperfect as a part and ‘finds completion in its whole’. Therefore, as Aquinas says, ‘the soul is more perfect in its natural being when it is in the whole’. Given his affirmation that the body perfects the soul, this Aquinas would probably deny that the union is in vain. Whatever its merit or demerit (more on this below), this view on the human soul-body union is recognizably different from the view in ST I q. 84, a. 4 and q. 89, a. 1: in this InSent text, the body perfects the soul’s natural being but not its understanding; in ST I, the body perfects the soul’s understanding but not its being.

Now, I would argue that Aquinas’s position on the perfection of the separated soul’s natural cognition in the InSent text is incompatible with his position in ST I, q. 89, a. 1. Recall that I summarized Aquinas’s position in ST I, q. 89, a.1, co. as follows:

In the InSent text, Aquinas rejects (M)(b). This can be seen in the following quote,

This quote will be the focus of the rest of this section. In this quote, Aquinas states that ‘the soul separated from the corruptible body can act more perfectly than when it is united to it’. This is clearly an (S)-claim. A question naturally arises: what does ‘more perfectly’ mean? Can we adopt the reconciling strategy to render this (S)-claim compatible with (M)?

My answer is no. To see why, we need to notice the words ‘just as’ in the quote. Aquinas says that the union with the glorified body helps the beatified soul act more perfectly, just as the separation from the perishable (or corruptible) body helps the soul act more perfectly. Suppose Aquinas only, or primarily, attributes a more perfect mode of understanding to the separated souls here. In that case, Aquinas should mean that the union with the glorified body will change the mode of understanding just as the separation from the body. The difficulty of adopting the strategy here is precisely this: for Aquinas, separation from the perishable body changes the soul’s mode of understanding, but the union with the glorified body does not change the beatified soul’s mode of understanding, so this reading does not take ‘just as’ into account. Recall that separation from the perishable body changes the soul’s mode of understanding in that the mechanism of understanding changes: when embodied, phantasms are essential; when separated, the phantasms have no role. However, for both the embodied and disembodied saints, the mechanism of the beatific vision is exactly the same: receiving the light of glory and, thereby, God’s essence.Footnote ³⁶ Thus, the union with the glorified body does not change the saints’ mode of understanding. In sum, Aquinas’s words ‘just as’ suggest that, by ‘more perfectly’, Aquinas should mean something other than understanding by a more perfect mode.

If ‘more perfectly’ does not mean understanding by a more perfect mode, then what does it mean? As I see it, it should mean having a more perfect understanding overall. In that case, we can naturally read the quote as follows: ‘Separation from the corruptible body results in an overall more perfect cognition that is unattainable before the separation, and union with the glorified body similarly results in an overall more perfect beatific vision that is unattainable before the union’. This reading coheres better with the intended goal of Aquinas in this text, which is to argue that the saints will have a more intense beatific vision after uniting with the glorified body. Also, claiming that two things are analogous in one respect does not require the two things to be analogous in all respects. Thus, the fact that only one of the two cases involves a change in the mode of understanding does not count against my reading.

However, the immediate consequence of my reading is that the quote contradicts (M)(b), i.e., separation from the (perishable) body does not make available a cognition overall more perfect than the cognition an embodied human soul can attain, which is part of Aquinas’s position in ST I, q. 89, a. 1. In other words, given my reading, Aquinas’s position on the perfection of the separated soul’s natural cognition in InSent IV d. 49, q. 1, a. 4, qc1 is incompatible with his position in ST I, q. 89, a. 1.

In fact, given my reading of the InSent text, it is plausible that the Aquinas in ST I, q. 89, a. 1 would completely repudiate the view on the human soul-body union in InSent IV d. 49, q. 1, a. 4, qc1, according to which the body perfects the soul’s natural being but impedes its understanding in a way incompatible with (M)(b). In his ‘doubt’ in ST I, a. 89, a. 1, Aquinas argues that if separation from the body leads to an overall more perfect understanding, God should not have united the human body and soul since the union would be in vain. In other words, for the Aquinas in the ST text, the union is not in vain only if the separation does not lead to an overall more perfect understanding. Thus, for the Aquinas in ST I, q. 89, a. 1, the human soul-body union would be in vain given the position in the InSent IV text. The alleged contribution of the body to the soul’s natural being is not a reason for God to create human beings.Footnote ³⁷

To sum up, Aquinas’s position on the perfection of the separated soul’s natural cognition in InSent IV d. 49, q. 1, a. 4, qc1 is incompatible with his position in ST I, q. 89, a. 1. The incompatibility lies both in the perfection attributed to the understanding and in the two markedly different views on the implication of the human soul-body union for the perfection of the soul’s understanding.

4. Conclusion

Before I end this paper, I would add two remarks, one to clarify what (I think) I have achieved in this paper more precisely and the other to identify the most important takeaway from this paper.

First, if my reading of the texts holds, then Aquinas expounded two incompatible positions on the perfection of the separated soul’s natural cognition at two different places and two different times. This strongly suggests that he changed his view on the issue.Footnote ³⁸ However, given the number of relevant texts I have not dealt with in this paper, I am aware that I have not established my reading of InSent IV d. 49, q. 1, a. 4, qc1 conclusively, nor have I ruled out the possibility of reconciling two teachings in the texts by other means. I believe I have established, for now, nothing more than the prima facie plausibility of Aquinas’s change of view. Yet, this prima facie plausibility should suffice to shift the burden of proof to those who affirm that Aquinas’s view underwent no radical change. To meet the burden of proof, providing a plausible alternative reading of InSent IV d. 49, q. 1, a. 4, qc1 compatible with Aquinas’s position in ST I, q. 89, a. 1 is minimum.

Second, while this paper has primarily focused on the separated soul’s cognition, I believe what is at stake is Aquinas’s evolving reflection on the human soul-body union. As I see it, Aquinas once struggled to identify the true nature of the human soul-body union and its implications. His reflection on the human soul-body union evolved, and he adjusted his views on other issues accordingly. I believe the separated soul is only one of those issues, which means that there is more for us to learn and explore about this evolving reflection of a mastermind.Footnote ³⁹