History of PHilosoPHy Quarterly Volume 34, Number 2, April 2017 115 AQUINAS AND ARISTOTELIANS ON WHETHER THE SOUL IS A GROUP OF POWERS Nicholas Kahm In the Aristotelian tradition, there are two broad answers to the basic question "What is soul?" On the one hand, the soul can be described by what it does. From this perspective, the soul seems to be composed of various different parts or powers (potentiae) that are the principles of its various actions. On the other hand, the soul seems to be something different, namely, the actual formal principle making embodied living substances to be the kinds of things that they are. Contemporary Aristotelians are split on how to interpret Aristotle: Anna Marmodoro (2013, 18), Thomas Johansen (2012, 81), and most others argue that the soul is nothing but a kind of cluster or group of powers. Rebekah Johnston (2011), however, strongly disagrees and argues that the soul is only the actual principle of embodied substance.1 Aquinas provides a novel and neglected solution to this problem and would argue that both sides are partly right but that either side is insufficient without the other. The first part of this paper discusses how Aquinas can simultaneously hold that the soul as form is not a group of powers while also holding that the soul as mover or potential whole is composed of powers. The second part discusses why he would disagree with Johnston's arguments that the soul cannot be a group of powers, and the third part discusses why he would disagree with arguments that the soul is nothing but a group of powers. The fourth part explains in what sense he agrees with both sides and why he thinks that both perspectives are necessary to give a full account of what soul is. i Six times (by my count), Aristotle himself raises the question of whether the soul is composed of parts, and if so, how the soul has parts. For example, HPQ 34_2 text.indd 115 6/29/17 11:15 AM 116 HISTORY OF PHILOSOPHY QUARTERLY We must consider also whether soul is divisible or is without parts, and whether it is everywhere homogenous or not; and if not homogenous, whether its various forms are different specifically or generically. . . . Further, if what exists is not a plurality of souls but a plurality of parts of one soul, which ought we to investigate first, the whole soul or its parts? It is also a difficult problem to decide which of these parts are in nature distinct from one another. Again, which ought we to investigate first, these parts or their functions, mind or thinking, the faculty or the act of sensation, and so on?2 In this passage, Aristotle asks whether the soul is divisible into parts and, if it is divisible, whether these parts are perhaps different souls. Aristotle has thus left a few options on the table: there may be many souls, there may be many parts in one soul, or perhaps there are no parts at all. Let us take the first of these off the table for Aquinas, namely, the possibility that there are many souls or substantial forms in one composite. Aquinas, unlike almost everyone else of his time, argues that there is only one substantial form in any substance. For Aquinas, substantial form is what makes a being actually exist and grants it its substantial unity, and it is also what makes a substance be a particular kind of substance. Furthermore, substantial form, which is act, directly informs prime matter, which is pure potency. Accidental forms, in contrast, inhere in and qualify substances in some particular way, for example, whiteness inheres in this substance and thus makes it white. Aquinas criticizes those who posit a multiplicity of substantial forms along two main lines. First, he holds that they are confusing the accidental and substantial orders, since, whenever one form comes to another, one of them must be a substantial form and the other must be an accidental form that inheres in a substance. For example, there cannot be one form of rationality and another of animality that come together to make a rational animal, since one of these forms must inhere in the other-thus, one must be the substance, and the other an accident. If there were two such forms, then either I would be essentially animal and accidentally rational, or I would be essentially rational and accidentally animal; but (following Aristotle) I am essentially a rational animal. Aquinas's second line of criticism follows the first. He asks: If a substance is composed of two substantial forms, what accounts for the two forms being one substance? How do we account for the substantial unity that holds the entire being together? To put it simply, if there are two substantial forms, how can we explain that it is one substance rather than two? Aquinas thinks there is no answer to this question. There can only be one substantial form; anything else predicated of a substance, if it is a really distinct form, must be an accident that inheres in that substance.3 s__ n__ lc HPQ 34_2 text.indd 116 6/29/17 11:15 AM AQUINAS AND ARISTOTELIANS AND THE SOUL 117 But Aristotle left two other possibilities on the table: either there are parts to the soul, or there are no parts to the soul. Aquinas argues that both of these are in a certain sense correct. Let us first consider his reasoning for not positing parts to the soul. For Aquinas, because the soul directly and immediately informs matter,4 there is no way to divide it into parts. The soul equally informs the whole body and each part; for example, there is not more soul in my eye than in my intestine, since these are equal with respect to the soul's precise role of informing matter (QDA 10[Leon.24/1.90.147–50:178–82]). If, however, the soul were only the form of a part or the form of some parts of the body, it would not be the form of the whole body but only of that part or of those parts of the body (ibid.). Qua form of the body or matter, the soul is unified and simplex,5 as Aquinas puts it. If the soul is to be defined solely as the form of the body, then there is no reason to divide the soul into parts. There is, however, another sense in which the soul does have parts. What distinguishes animate from inanimate substantial form is precisely life, which is characterized as a nature that has its own source of motion (Physics II)-specifically, nature is that which moves itself (In De an. 2.1.Leon.45.1.70.177–78; compare Aristotle, De Anima 412b16–17). In other words, things with soul move themselves, while things without soul do not. This is why, according to Aquinas, Aristotle includes life in his definition of soul: "[T]he soul is an actuality of the first kind of a natural body having life potentially in it" (De Anima 412a27–30). Selfmotion requires dividing the soul into parts, for when one says that the soul moves itself, there is a distinction between the soul that moves and the soul that is moved ("itself"). Since this obviously refers to the same soul, Aquinas infers that this distinction between moving and being moved must refer to different parts within the same soul.6 Aquinas bases his inference that these must be different parts on Aristotle's arguments in Physics VIII concerning the axiom that everything that is moved is moved by another. If the axiom is true, then the possibility of self-motion must be rejected, for if something moves itself, then it is not moved by another. But Aquinas and Aristotle are careful to point out that they are not denying the kind of self-motion established in Physics II, that is, the self-motion of nature as that which can move itself. Aquinas's argument assumes the general division of being into act and potency and takes its starting point from motion, which is the act of potency as potency. Granting this, it follows that nothing can reduce itself from potency to act, since then it would simultaneously be in act and in potency in the same way and at the same time, that is, it would both be and not be at the same time and in the same respect, which is a contradiction. Thus, everything that is moved (reduced from potency to act) is moved by another (which is actual). Since we cannot regress __s __n lc HPQ 34_2 text.indd 117 6/29/17 11:15 AM 118 HISTORY OF PHILOSOPHY QUARTERLY to infinity in per se ordered causes, we must come to some cause that is not moved by another.7 This cause that is not moved by another is moved by itself; it is moved per se in the strongest sense.8 This kind of per se causality is only intelligible as the negation of per accidens motion (In VIII Phys.7.535.1022), and because we cannot help but think of such a cause as reducing itself from potency to act, it is, in a certain sense, unintelligible to us. As is well known, Aquinas argues that there can only be one such cause, namely, God; he reasons to a God who is perfect and completely actual without any potency. On Aquinas's view, God's actions involve no reduction from potency to act and, thus, are not, strictly speaking, motions.9 In contrast to this kind of self-motion, when any finite being moves itself, because it is composed of act and potency, it moves itself by means of parts; that is, one part is actual, and it reduces to act some other part that is in potency. Strictly speaking, this kind of self-motion is per accidens in the particular sense of a motion that can only happen by means of its part.10 Thus, the axiom that everything that moves is moved by another also applies, as both Aquinas and Aristotle insist, to the parts within a natural self-mover (In VIII Phys.10.553.1051; Aristotle, Physics 258a23–25). Regardless of what kind of self-motion is meant-for example, nutritive, sensitive, or rational-in none of these possible cases does the first cause of motion come completely from the agent.11 This is why any soul, as it is a principle of motion, must be composed of parts.12 Aquinas thus distinguishes between two different causal roles of the soul, namely, the soul as form (forma) and the soul as mover (motor). As the form of the body, the soul has no parts (it is simplex), but as mover, that is, as the principle of motion or operation, it does have parts (it is multiplex). This division of the soul into parts, Aquinas says, is according to operation (secundum operari).13 Both Aristotle and Aquinas are very explicit that these parts of the soul are its powers.14 Aquinas says that they are parts of a potential whole and that the powers of the soul are its potential parts.15 The soul, according to Aquinas, is a certain potential whole (anima enim est quoddam totum potenciale), and he even goes so far as claiming that this is also Aristotle's personal position (In I de an.14.Leon.45/1.65.63–75; QDA 10 ad 9). Be that as it may, for Aquinas the potential whole is a whole of power, that is, a kind of sum total of what the soul can do, its total power (totalis virtutis eius), in the sense in which it might be said that the power of the bailiff is part of the total power of the royal court.16 The soul as a potential whole is the soul considered as it has various powers that operate in unison to perform highly complex operations in an integrated manner. s__ n__ lc HPQ 34_2 text.indd 118 6/29/17 11:15 AM AQUINAS AND ARISTOTELIANS AND THE SOUL 119 Each power plays its proper role in the power of the creature as a whole. In a late passage in his commentary on Aristotle's De sensu (1268–70), Aquinas gives a clear account of this; note the hierarchy, order, and mutually exclusive but complementary operative roles of the soul's parts: [W]herever there are diverse ordered powers, the inferior power is related to the superior power in the manner of an instrument because the superior moves the inferior. For action is attributed to the principal agent through the instrument, as we say that the builder cuts with the saw. It is in this way that Aristotle says here that the common sense senses through sight and hearing and the other proper senses, which are diverse potential parts of the soul (Sentencia libri De sensu 1.18.Leon.45/1.89.130–40). Nature or life understood as ordered and acting for the sake of an end, but not immediately operative, must be composed of a such a complicated ordered group of really distinct powers. It is this ordered hierarchy of material and immaterial powers, ordered in the sense of operating in unison, with each power playing its part for the sake of the person's end, that Aquinas calls the "potential whole."17 It is worth noting that, in the particular case of the powers or parts of the potential whole, which are accidents, the subject not only serves as the receiving principle in which they inhere (this is common to all accidents), but the subject is also included in the definition of the accident as its active and efficient cause.18 Because there must be some likeness between cause and effect, in this case, the soul and its powers, we can learn something of a person's soul from his accidental powers, for example, that he is rational, which signifies that this kind of soul always produces and has rational powers. That is how Aquinas explains Aristotle's claim (De anima 1.1.402b21–403a2) that we have knowledge of the soul through its properties or powers and that there is no real definition of the soul without its properties or powers.19 Thus, there are two ways of understanding what the soul is. As the form of the body (or the essentia animae) and the principle of substance, the powers of the soul are excluded from our understanding of the soul. But as the soul is a mover or potential whole, however, the powers of the soul are included in our understanding of soul. But it is the same soul that is a principle in two different ways, that is, as the formal principle of material substance and as the principle of powers and operations.20 ii Let us now consider Rebekah Johnston's arguments that that the soul cannot be composed of parts. Johnston has three main arguments. First, she argues that, because the soul is a form (De anima 412a20–21) and __s __n lc HPQ 34_2 text.indd 119 6/29/17 11:15 AM 120 HISTORY OF PHILOSOPHY QUARTERLY form is actual and not potential (Metaphysics 1043a25–28), granting that powers as potentialities are potential, the soul cannot be a group of powers without making the soul a potential existent (Johnston 2011, 191–92). Johnston suggests that the term "first actuality," which Aristotle often uses to describe the soul as it is actual, is not defined in terms of a further actualization (2011, 190), but Aquinas would strongly disagree with her on that point. The term "first actuality" is precisely related to a "second actuality" (ST I 76.4 ad 1), for, otherwise, one would just use the term "actuality" rather than "first actuality." The whole point of Aristotle's example of knowledge as a first actuality is that knowledge is actually possessed, but it is precisely the kind of thing that is also in potency to a further secondary actualization, namely, knowing.21 Thus, if the soul is a first actuality that is in potency to a second actuality, the powers of the soul must somehow be included in soul. Once Aquinas's distinction between the soul as form and as mover is made, the soul can be classified among both potential and actual existents.22 As the form of the body, it is actual as actualizing body; as a potential whole, however, it is considered as it is in potency to its further actualization through its parts or powers.23 The latter presupposes the former, of course, but there is no metaphysical inconsistency once one grasps the two different senses of soul. Second, Johnston points out that, in Metaphysics 9 (1046a21–28 and a36–b4), Aristotle argues that powers are in a subject, and she asks: What is this subject? There are three possibilities: the soul, the body, or the composite of soul and body. If the powers are the soul, however, then they cannot be in themselves. Nor can they be in the body because the soul is precisely what makes body be body; nor can they be in the composite, since the composite presupposes soul. Since there is apparently no subject for the soul as a set of powers to be in, the soul cannot be a set of powers (Johnston 2011, 193). Qua form, for Aquinas, the soul is in the category substance, and the powers of the soul are in the category of quality.24 The powers of the soul are accidents that inhere in the soul itself and, in some cases, in the composite (ST I. 77.6). In this sense, the powers of the soul are not the soul itself (essentia animae); rather, the soul is their subject. As the soul is a mover, however, the powers of the soul are included in the definition of the soul. Thus, we may affirm Johnston's argument that the soul qua form is actual and cannot be a set of powers, but we may reject it as the soul is a mover.25 As her third argument, Johnston points out that the soul is in the category substance and substance is first in ratio in the categories.26 However, if the soul is a set of potencies, they are necessarily posterior in ratio to their second acts, which themselves are in a different category s__ n__ lc HPQ 34_2 text.indd 120 6/29/17 11:15 AM AQUINAS AND ARISTOTELIANS AND THE SOUL 121 (action; Categories 4, 2a3). In other words, if the soul is set of potencies, then, claims Johnston, this undermines the argument for the primacy of substance as the first category (Johnston 2011, 193). Following Aristotle, when Aquinas divides being between substance and accidents, he is dividing being into beings that are their own centers of existence and those that only exist in other substances. This is why the prime referent of being in the categorical schema is always substance, since substance is always in the definition of an accident as the cause of that accident's being.27 As the substantial form of the body, the soul performs the role of granting and causing substantial being and unity, informing the body, and serving as the subject or supposite for accidents. This is one kind of metaphysical or categorical primacy; however, teleological primacy, which is quite different, does not undermine this. When the soul is understood as composed of powers, it is true that the second act or operation has primacy, since the second act is primary in the sense that it is the final cause (In I de an.1.Leon.45/1.71.303–5). In general, the final cause, according to Aristotle and Aquinas, is the causa causarum. The claim, however, that the final cause is the most important of the four causes is not a metaphysical claim about the kind of being at stake. The metaphysical primacy of substance in the categorical schemata is not threatened by the fact that that substance is not primary in every way. Simply because a substance is the kind of thing that is teleologically ordered to some particular action, it does not follow that action must have the same kind of metaphysical gravitas as substance. In sum, Aquinas would grant Johnston's three arguments in terms of the soul as form, but not in terms of the soul as mover. iii Most contemporary Aristotelians, however, hold that the soul is nothing but a holistically unified cluster of powers.28 For example, Anna Marmodoro argues that substances are functional wholes, comprising parts that are, however, reidentified when they become parts of a substance. By this, she means that when something "enters" into the constitution of a substance, it does not retain the same identity it had when it was not part of the substance; rather, it is reidentified as a functional part of the substance it now constitutes. The characteristic operation or function of the substance as a whole drives the reidentification of its constituents. Marmodoro states, "Substantial form according to Aristotle is an operation on the elements of a substance, stripping them of their distinctness, rather than being an item in the ontology," and "[a] substance is all its parts, re-identified" (2013, 18). What are these parts? For Marmodoro, they are the active and passive causal powers, which __s __n lc HPQ 34_2 text.indd 121 6/29/17 11:15 AM 122 HISTORY OF PHILOSOPHY QUARTERLY are relative (Metaphysics, 1020b26–32), that is, pros ti (towards something) monadic properties. Active powers are relative to passive powers, and passive powers are relative to active powers, these causal relata are ontologically interdependent as mover and moved, and causation consists in the mutual activation of both powers. On this reading, the soul is a kind of causal functional unification of a highly sophisticated complex of active and passive powers, a kind of division of labor working together holistically in a metaphysically seamless way (Marmodoro 2014, Chapter 1). In Aquinas's terms, substantial form on this understanding is merely the potential whole or mover. Thomas Johansen, who holds a similar position, asks the following question: The soul itself is supposed to be a substance, but we are now saying that it is itself composed of capacities for change which seem not all at least to belong to the same categories. That is to say, categorically different items enter into the essence of the soul. Does the soul not end up as a categorical hodgepodge of entities? (2012, 81) Johansen's ultimate answer is affirmative. Each kind of soul is a group of powers unified and related to each other as form to matter, that is, as act to potency (ibid., Chapter 3). In other words, for Johansen, the soul is all powers, a functionally organized categorical hodgepodge. Furthermore, for both Johansen and Marmodoro, the body itself qua matter is also made up of powers (Marmodoro 2013, 12–18; Johansen 2012, Chapter 1). As Marmodoro puts it, "[T]he ultimate level of reality is the fundamental powers (hot, cold, wet and dry)" (2013, 11–12). Thus, hylomorphism, the relation between matter and form as potency and act, is, on their understanding, ultimately reducible to the clustering of interrelated powers along the lines of act and potency. From a strict Aristotelian perspective, one wonders how these authors would respond to Johnston's unanswered objections, which have strong textual support. As of yet, there has been no response. Aquinas himself would argue against them on more philosophical grounds within a broadly Aristotelian framework. For him, the powers of hot, cold, wet, and dry are the powers of the most basic substances, the elements,29 which cause those powers. Because powers presuppose substantial forms as their cause, one cannot argue that these powers somehow cause or are the substantial form itself. This is why there aren't free-floating powers that cluster into this substance and then cluster into that substance. Even if there were, however, one would still have to explain how they clustered into this substance rather than that one. In other words, if the powers of one substance are to become the powers of another substance through being reidentified, there must be something else beyond the powers that s__ n__ lc HPQ 34_2 text.indd 122 6/29/17 11:15 AM AQUINAS AND ARISTOTELIANS AND THE SOUL 123 accounts for this new reidentification and clustering, namely, substantial form. Appealing to a substance's operations to account for this clustering must fall short because one must ask how they so clustered to be able to so operate in the first place. In other words, there must be something of a higher ontological type, namely, substantial form, that causes and unifies the powers.30 Nor can matter be composed of powers. In the illustrative case of substantial change at the elemental level, for example, fire turning into air, there must be some other more elemental potency principle underlying substantial generation, namely, prime matter.31 In other cases of generation, it seems that one can appeal to another more fundamental potency principle out of which some substance might come to be (for example, bronze or earth), but in the case of the substantial generation of elements, there is simply nothing more fundamental to appeal to than the elements themselves. Following Aristotle's response to Parmenides, Aquinas concedes that something cannot come from nothing. He divides being into act and potency, and, in the case of substantial generation, Aquinas argues that the potency principle in substantial generation is not powers (whose existence presuppose that substantial generation has already taken place), but rather, relative nonbeing or prime matter, which is not pure nothingness but rather pure potency.32 On Aquinas's reading of substantial generation, the old substance and its powers are destroyed, and a completely new one and its powers come to be.33 If the potency principle in substantial generation were to be any other form already enmattered (sperm, menstrual fluid, elements, powers, or whatever), then one would have two or more substantial forms in a composite,34 and one would be forced back to the question of substantial unity, which we have already discussed. Aquinas does place the active and passive powers in the category relation, but they are also in the category of quality. A power can be considered a quality insofar as it has inesse (existing in) and as a relation insofar as it has adesse (that is, existing toward, Aristotle's pros ti), but it is exactly the same accident that can be considered from both perspectives.35 Marmodoro (2013, 2014), however, only describes powers as existing toward rather than existing in because of her commitment to what she calls a "pure powers" ontology, that is, a purely dispositionalist and noncategorical account of powers. For readers less familiar with the contemporary analytical distinction between categorical and dispositional properties, the term "categorical" does not refer back to Aristotle's Categories, but rather means categorical as opposed to hypothetical. Thus, a categorical property is a property that the subject actually has, and a dispositional property is one that the __s __n lc HPQ 34_2 text.indd 123 6/29/17 11:15 AM 124 HISTORY OF PHILOSOPHY QUARTERLY subject has in potentiality. For instance, to say that a diamond has the power to scratch glass is not to say anything about an actual categorical quality or property of the diamond itself; rather, it is a dispositional description signifying that a diamond can potentially scratch glass if (or on the condition or hypothesis that) it is raked across the surface of glass. I think the way forward along lines that are more congruent with Aquinas's thought is the "identity theory of powers" advocated by C. B. Martin, John Heil, and William Jaworski.36 This theory argues that one and the same property has both categorical and dispositional descriptions and theoretical roles; that is, the same power can be described both as an actuality and as a potentiality, but in different respects. Thus, humans actually have the power of sight, but it is not actual when our eyes are closed. We can describe the categorical actuality of that power in one way, as inhering in the person or as the structural-material makeup of its organ, the eye, but the very same power is in potency to being actualized or not, that is, to seeing or not seeing. In the latter sense, we are speaking of the causal-dispositional role of that very same categorical property. We can distinguish between categorical and dispositional facets, between its actuality and potentiality, but it is the same actual power that is in potency to a further actualization simply because it is that kind of a thing. That is, it is precisely because a diamond is actually or categorically hard that it has the dispositional power to scratch glass. For Aquinas, the ontological unity of the soul's parts is only truly grasped insofar as the parts are qualities and have inesse and not insofar as they are relatives and have adesse. Aquinas flatly denies that there is any reason to posit ontological unity between dispositional descriptions of movers and moved.37 Sometimes movers and moved, active and passive powers, are in the same substance, but obviously sometimes they are not. Consider, for example, the external senses. On the one hand, we may consider them as powers of the soul in the sense in which they actually inhere in this substance. On the other hand, we may consider them as they are related to and moved by external sensible qualities. The later dispositional description will not help us ground the unity of the soul's parts, but the former categorical one will. Substantial form, thus, is an "element in ontology" that unifies the soul's powers by causing them and by causing the substance in which they inhere.38 Without this perspective, it is impossible to argue for substantial unity or the metaphysical primacy of substance in Aristotle's categorical schema. iv Explanations of soul that lean heavily on powers and their operations have difficulty accounting for substantial unity; those leaning heavs__ n__ lc HPQ 34_2 text.indd 124 6/29/17 11:15 AM AQUINAS AND ARISTOTELIANS AND THE SOUL 125 ily on such substantial unity have difficulty accounting for the soul's manifold operations. Grasped as form, the soul is the principle of substance, subsisting, and its unity. But, for Aquinas, it also is axiomatic that esse is proportioned to operari, that is, substantial existence is for the sake of action, or, in even simpler words, this substance exists in this particular way so that it can act in this way.39 In this respect, the soul cannot simply be described as a substantial form but must also be described as a mover or potential whole. This is why one of the crucial roles of substantial form is causing its various powers (which inhere in that substance) and acting through these powers. Qua form, we need not consider the powers of the soul, for we are focused on how soul is the principle of material substances. Qua mover, we are rather focused on how this same unified living substance acts, and, from this perspective, our understanding of soul must also include its parts or powers. But we may consider soul in two senses, either without powers as it is the form or the body and the principle of substantial unity, or as the soul causes its powers and operates through its powers: but Aquinas insists that, ultimately, it is the same soul that can be considered as the principle of these two different effects, namely, substance and operation. According to Aquinas's view of the history of philosophy, Plato (like Marmodoro and Johansen) simply grasped the soul as mover and not as an Aristotelian formal cause.40 But Aquinas nevertheless thinks that Plato was half right, and Aquinas would undoubtedly agree with many of Marmodoro's and Johansen's formulations about the extraordinarily sophisticated holistic complex of the powers of the soul. Likewise, he would agree with Johnston's reasons for excluding powers when considering soul as the formal principle of substance. Concerning the contemporary aporia among Aristotelians vis-à-vis the soul and its parts, both sides build compelling arguments on particular sets of texts supporting their opposing views. It seems that either Aristotle is inconsistent or that the aporia requires a resolution that looks something like Aquinas's. Although most Aristotelians will be skeptical of Aquinas's claim that this was Aristotle's own solution, nevertheless, no one doubts Aquinas as a serious reader of Aristotle, and nothing in Aquinas's solution is anathema to Aristotelian thought in general, although some will inevitably object to this or that. Be that as it may, Aquinas's neglected solution is undoubtedly of historical interest, and granting the increasing interest in hylomorphism, I think it should also merit a hearing in its own right as one possible and plausible philosophical position.41 St. Michael's College, Vermont Keywords: Aquinas, Aristotle, soul, powers, parts __s __n lc HPQ 34_2 text.indd 125 6/29/17 11:15 AM 126 HISTORY OF PHILOSOPHY QUARTERLY NOTES 1. For more literature, see n28 below. 2. Aristotle, De Anima 1.1.402b1–13, 641–2; cf. ibid., 1.5.411a26–b31, 655–56; 2.2.413b14–414a4, 658–59; III.9.432a15–b9; Nichomachean Ethics 1.13.1102a26–32 and 1102b24–5. 3. For Aquinas's best texts on the unicity of substantial form, see his QSC (Quaestio disputata de spiritualibus creaturis) 3; QDA (Quaestiones disputatae de anima) 9; SCG (Summa Contra Gentiles) 2.71; ST I 76, a. 3, 4, 6, 7. See Dales (1995); Pegis (1934); Wippel (2000, 327–51). 4. QDA 11 (Leon.24/1.100.250–52); In De an. 2.1 (Sentencia libri De anima) (Leon.45/1.72–73.368–89); QSC 3 (Leon.24/2.38–39.224–48). See White (1996). 5. QDA 9 ad 14 (Leon.24/1.85.483); ibid., 8 ad 14 (Leon.24/1.73.459–63); ibid., 10 ad 17 (Leon.24/1.94.401), for example. 6. In VIII Physic. c.10 (In octo libros Physicorum Aristotelis expositio, Marietti.553.1053): "Si igitur totum moveat se secundum totum, sequitur quod idem sit simul actu et potentia; quod est impossibile. Ex hoc ergo concludit principale intentum, quod moventis seipsum una pars movet et alia movetur." 7. For a presentation and discussion of these kinds arguments and their critics from a general metaphysical perspective, see Wippel (2000, 413–25 and 444–62). On the specific question of the impossibility of an infinite regress in per se causes, see Wippel (2000, 422–23, esp. n63) and Cohoe (2013). 8. For Aquinas, per se motion is a somewhat flexible term. Per se motion in the strongest sense is the sense in which a whole moves itself as whole, which is only applicable to God. But there is another kind of per se motion: this is motion in the sense in which an action is proper to a specific nature. For example, reasoning and willing are proper per se actions of the human being; see In VII Phys.c.7.7 (Marietti.535.1023). A related but different sense is involved in Aquinas's claim that per se actions only come from beings that per se subsist; see SCG II.51 (Leon.manualis.144). Here he has in mind an immaterial mode of existing and its consequent actions. 9. In Sent. (Scriptum super libros sententiarum magistri Petri Lombardi)1.8.3.1–2. See also ST I 9.1–2 and SCG 1.13 and ST I 2.3. 10. See n6 above. 11. In Aristotle, it sometimes appears that one part of the soul is an unmoved mover, but Aquinas argues against this (when it is taken too strictly) on the grounds that, if the causal chain indeed truly stopped there, such a part of the soul would have to be God (pure act, not moved by another). For Aquinas, if one follows the various parts of the soul backward in the causal chain, the only serious candidate for this role is the will, which, Aquinas argues (using a passage from Aristotle's Eudamian Ethics), is ultimately moved instinctually by God (see QDM [Quaestiones disputatae de malo] 6 [Leon.23.149.407–17]). For a recent interpretation and discussion of the Aristotelian scholarship on this s__ n__ lc HPQ 34_2 text.indd 126 6/29/17 11:15 AM AQUINAS AND ARISTOTELIANS AND THE SOUL 127 passage in the Eudemian Ethics, see Gabbe (2012). For Aquinas's use of this text, see Hoffmann (2007) and Shanley (1998). On the conflict between God's motion and evil human choice, see Grant (2009). For Aquinas on the starting point of motion in the nutritive/vegetative powers, see, for example, QDA 9 and ibid., ad 6; ibid., 10 ad 4, 5. The origin of the motion of the sensitive powers is more complex, since there can be several different and sometimes simultaneous sources, for example, sense cognition, the heavenly bodies, reason, and will; but in none of the possible sources of sensitive motion does the soul move itself as a whole. 12. For the full argument, see In VII Phys.c.7 (Marietti.535.1022; ibid., 537.1028); In VIII Physic.c.10 (Marietti.553.1051–53); In I De an.c.6 (Leon.45/1.28.57–94); In II De an.c.1 (Leon.45/1.73.380–92). For Aquinas's other arguments, see Wippel (2000, 285–88). I am intentionally ignoring the argument in QDA 12 because I'm not fully persuaded that it works. King (2008, 265) characterizes this as Aquinas's best argument, but I will simply note that King missed this argument from the broad concept of motion-Aquinas's strongest argument for the necessity of positing powers of the soul-which is rooted in his basic metaphysics of act and potency. For another reply to King's paper, see Wood (2011). 13. QDA.9.ad14 (Leon.24/1.85.483–92): "anima sit forma simplex secundum essentiam, est tamen multiplex uirtute secundum quod est principium diversarum operationum. . . . oportet esse ordinem in partibus secundum ordinem operationem." Cf. In I de an. 1 (Leon.45/1.73.387–92); QDA 8, ad 14 (Leon.45/1.73.459–63); QDA.9 (Leon.24/1.81.246–56); ST I 76.5 ad 3; etc. It should be noted that, for Aquinas, these are not the only two causal roles that the soul plays. It is also a principle of subsisting, which is not reducible to the other two roles; see SCG II, c. 51, for a good summary of what it means for a form to subsist. 14. Aristotle, De Anima, 413b27–32. For a description of Aquinas's powers, see ST I, qq. 78–82. 15. Although the term "potential whole" seems to have come from Boethius, Aquinas was undoubtedly also influenced by his teacher Albert the Great. See Albert, De IV coaequaevis, IV.36.2, part.1, sol. Borgnet v. 34, 540. See Boethius (1998, PL 64:888, 38–41) and Magee's comments on 144–46. For a discussion of Boethius's text, see Arlig (2006) and Hasse (20082). For Aquinas's division of wholes and parts, see QSC 4 and 11 ad 2; QDA 10; ST I 76.8 and 77.1 ad 1. See also Svoboda (2012). 16. QSC a.11 ad 19 (Leon.24/2.123.462–65); cf. In I de an. 14 (Leon.45/1.65.64– 68). 17. QDA 13 ad 7 (Leon.24/1.121.407–14). QDA.9 (Leon.24/1.82.283–98); In de an. 1.14 (Leon.45/1.67–69); QDA 13 ad. 9 (Leon.24/1.121.426–31); QSC 11.ad 2 (Leon.24/2.120.326–29); QDA 10 (Leon.24/1.91–92.249–52): ST 77.4. 18. Super Boetium De Trinitate (de trin.) 5.4 ad 4 (Leon.50.156.277–86). For Aquinas, there is a necessary causal connection between the soul and its powers or properties, for the powers of the soul have a permanent cause in their subject, __s __n lc HPQ 34_2 text.indd 127 6/29/17 11:15 AM 128 HISTORY OF PHILOSOPHY QUARTERLY QDA.12 ad 7 (Leon.24/1.111.265–87); that is, they are always being caused by soul or substantial form. This guarantees that, as long as the subject exists, the powers do so as well. That is why they are said to be inseparable from the subject, and it is this necessary causal relation that allows Aquinas to predicate the powers of the soul. Perler (2015, 128) denies that the soul efficiently causes its powers, and some, for example, Pasnau (2002, 152, 167, passim), think that the soul causing its powers is mysterious. But for contemporary philosophers who grant the existence of form (structure, organization, arrangement, order, or configuration; see Jaworski [2016, Chapter 14] for a discussion of the various extant positions), many also believe that these structures are responsible for certain organized parts, for example, the eye, brain, or heart. For instance, Jaworski himself argues that composition happens only when a structured individual configures the materials that compose it, and I am the only individual located exactly where I am that is engaged in that configuring activity. It is true that located exactly where I am there are also numerous biofunctional parts such as my heart, brain, and kidneys, but the existence of these parts depends on my own existence. (2016, 330) For Aquinas, this form or structure is always actualizing or efficiently causing these parts or powers, and Aquinas uses the term "flowing" (because he inherited it from Albert the Great) to describe this causal phenomenon. If this is a real problem for Aquinas, then any philosopher (and there are many) who holds that form, structure, configuration, and such somehow cause its parts has the same problem. For Aquinas's views on how we can predicate the powers of the soul, see In I post.an.14 (Leon.1/2.53–54.14–46); QDV (Quaestiones disputatae de veritate) 10.1(Leon.22.1.296–97.107–11); and cf. Aristotle's On The Heavens, I, c.11, 281a7–15. For the Aristotelian provenance of this way of thinking, see De anima I.402b22–25, and Aquinas comments at QDV 10.1(Leon.22.1.296–97.107–11); ST I.77.1.ad7; ST I, 85.1. Note that the different souls, that is, intellective, sensitive and nutritive are clusters of powers of the potential whole named from the highest powers; see ST II-II.48.1; In I de an.1 (Leon.45/1.7.231–46); QDA.19.ad 5 (Leon24/1.166.259–71); Quaestiones disputatae de potentia, 3.11, ad 2 (Marietti, 75); ibid., 3.11, ad 2 (Marietti, 75)-this is how Aquinas interprets Aristotle's obscure remarks (De anima 414b28–31) about different souls being include within each other as geometrical forms. 19. In I de an. 1(Leon.45/1.7.250–60:268–74). Cf. In I de an. 9 (Leon.45/1.44– 5.82–89); In I de an.11(Leon.45/1.56.197–200). 20. QSC 3 ad. 7(Leon.24/2.45.500–502): " sicut enim eadem est secundum substantiam anima, que est motor et forma, set differt ratione." QDA.9 (Leon.24/1.81.246–56); QDA.9 ad 2(Leon.24/1.83.324–30). For a fuller treatment of Aquinas's thinking on the potential whole, see Chapters 1–4 of my forthcoming book (2018) with The Catholic University of America Press. 21. Aquinas says that the example of knowledge differs from the soul because, although habitual knowledge is the immediate principle of knowing, the soul cannot be the immediate principle of operation but rather must operate by s__ n__ lc HPQ 34_2 text.indd 128 6/29/17 11:15 AM AQUINAS AND ARISTOTELIANS AND THE SOUL 129 means of its parts or powers. QDA 12 ad 14(Leon.24/1.111–12.316–20); QDA 9(Leon.24/1.81.246–50). 22. ST III. 75.6 ad 2: "anima est forma"; and ST I. 75.5: "forma, inquantum forma, est actus"; however, in ST I–II. 2.7: "Ipsa enim anima, in se considerata, est ut in potentia existens." 23. ST I. 77.1; In libros Aristotelis De caelo et mundo expositio 2.4(Leon.3.136); SCG II. 60; etc. Concerning Aristotle's example of habitual knowledge, see ST I–II. 49.3 ad 1. Note. In II de an. 1(Leon.45/1.71.315–19). 24. Aquinas puts the powers of the soul in the second species of quality: QSC II(Leon.24/2.119.257–58). For Aquinas's views on quality, see Kahm (2016). 25. ST I–II. 55.4; ST I. 77.1 ad 4; QDM 4.4 ad 3 (Leon.23.117.135–43). 26. Metaphysics 7.1.1028a36–b2, and 9.8, 1049b13–17. 27. For Aristotle on substance as the prime referent, see Physics, 1003b5–19; for Aquinas, see In IV Meta. 1 (In duodecim libros Metaphysicorum Aristotelis expositio) (Marietti.152–53.539–47). 28. For some earlier arguments that the soul is a group of powers see Ackrill (1972–73); Charlton (1980); Sorabji (1993, 163–64). Sorabji argues that, because Aristotle describes knowledge as both a first actuality (412a10) and a second potentiality (417a21–b2), we may infer that the soul is also both a first actuality and a second potentiality. But then Sorabji goes further and argues that, because Aristotle expresses dissatisfaction with the definition of the soul as an actuality, saying that the definition is merely a "sketch or outline" (413a10), he simply replaces it with a better definition, namely, that the soul is a set of potencies (163–64). But Aquinas thinks that, at that point in De Anima II, Aristotle had already sufficiently proved that the soul is a first actuality that has life in it potentially. See Cap. 1 of Aquinas's In II De anima. (Leon.45/1.67–73). Aquinas takes this supposed "sketchiness" simply to mean that it is generic. It tells us much about the soul, but there are more specific definitions of particular kinds of souls that must be filled out if we wish to know more about, say, quid sit anima hominis: In II de an.6(Leon.45/1.91.12–21). See also Corcilius and Gregoric (2010), who only discuss how the parts are related to each other. 29. QDA 12 (Leon.24/1.109.164–70); See also ibid., q. 1 (Leon.24/1.9.296–99). 30. I agree with Scaltsas that something of a different ontological type is needed to account for the unity of these parts. Cf. Scaltsas (1990, 587–88). 31. For a good discussion of this, see Aquinas's De principiis naturae (Leon.43.41.70–89), esp. lines 85–89: For a full discussion including all the important texts, see Wippel (2000, 295–371). For a helpful general argument for the existence of prime matter, see Jaeger (2014); see also Feser (2014, 160–208). 32. Aristotle is quite clear that powers cannot be matter; see Metaphysics, 1029a20–22, where he states that matter is "neither a particular thing nor of a certain quantity nor assigned to any other of the categories by which being is determined." See also Aquinas's In VII Meta. 7.2 (Marietti.233.1285)-that is, matter is not reducible to the active and passive powers considered as relations __s __n lc HPQ 34_2 text.indd 129 6/29/17 11:15 AM 130 HISTORY OF PHILOSOPHY QUARTERLY or qualities. For some other important passages for Aquinas on prime matter, see Aristotle's Physics, 190b1–4 and 191a3–12. 33. For example, see Aquinas's QDA 9 and QSC 3. 34. On sperm and menstrual fluid, see QDP 3.9 ad 9 and ad 11. For Aquinas, the elements remain virtually (in virtute) in the power of the substance; see De mixtione elementorum (Leon.43.155–57); de trin., 4.3, ad 6; Quodlib. 1.4.1 ad 3; ST I.76.4, ad 4; QDA 9, ad 10. All of this is to say that the prior substantial forms of the elements do not remain actually present in substances. 35. ST I.28.2. For a discussion and more texts, see Henninger (1987). 36. Heil (2003); Jaworski (2014), (2016); Martin (2007); Martin and Heil (1999). 37. QDA 9 ad 3 (Leon.24/1.83.331–32): "ex motore ex mobili non fit unum per se in quantum huismodi."; QDA 11(Leon.24/1.99.171–73); SCG.II.56 (Leon. manualis.151). 38. This is why Aquinas's philosophical arguments about the soul's parts always come after he has established that there can only be one substantial form in any substance and that this substantial form immediately informs prime matter and nothing else; thus, QSC 3 is presupposed for QSC 4; QDA 9 is presupposed for QDA 10; and ST I.76, aa.1, 3, 4, 6, and 7 are presupposed for ST I.76, a.8. 39. To put it most simply, QDV 9 (Marietti, 731): "omnis res est propter suam operationem." See also QDA 10, ad 2 (Leon.24/1.92.287–89); QDA 9 (Leon.24/1.82.278–80); QDA.9 (Leon.24/1.81.256–82); QDA 9 ad. 14 (Leon.24/1.85.482–94). 40. In II de an. 2 (Leon.45/1.76.153–57); ST I.76.3; ST I.76.7; QDA 11. 41. I wish to thank John Wippel and Anna Marmodoro for reading and commenting on earlier versions of this paper. REFERENCES Ackrill, John. 1972–73. "Aristotle's Definitions of psuchê." Proceedings of the Aristotelian Society 73: 119–33. 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