Abstract
Aquinas thinks that if we want to understand causal interactions between material substances, we cannot focus exclusively on agents and their active powers. In his view, there are also passive potencies which enable material substances to be acted upon. He claims that for every type of active potency, there is a corresponding passive potency. This article aims to clarify Aquinas’s views about the passive potencies of material substances. It recovers his thinking on three key questions: first, what is the basis or source of a material substance’s passive potentialities? Put otherwise, what constituents of material substances explain why they have capabilities for being acted upon? Second, how are a material substance’s passive potencies identified and distinguished from one another? Lastly, are passive potencies for undergoing action the same as a substance’s potencies for existing in determinate ways? For example, is a pot of water’s potentiality for being heated the same as its potentiality to be hot?
1 Introduction*
In contemporary philosophy, there has been much recent interest in the topic of causal powers.1 Prior to this revival, few contemporary philosophers held that material objects have real, irreducible causal powers by which they act upon and react to one another. Currently, however, there is a growing number of philosophers who argue that problems in understanding causation and the practices of natural science can only be resolved by a return to the pre-modern, Aristotelian view of material objects as endowed with real, active capacities. While contemporary power theorists agree that material objects must have active causal powers, there is disagreement about whether they must also have a distinct type of power which enables them to undergo action, namely passive power. Some have argued that such powers are unnecessary to explain how changes are caused.2 On this view, the burning of a log can be explained solely by appealing to a fire’s active power to burn. Others admit that there are passive powers, yet they claim that they do not differ in any way from active powers.3 According to this perspective, the log has a power to react to fire, which is essentially the same sort of power as the fire’s power to burn. Though the contemporary debate about passive powers is fairly new, there is a rich Aristotelian historical tradition which has been thinking about both active and passive causal powers for centuries. The goal of this essay is to retrieve the views of one particularly influential historical Aristotelian, Thomas Aquinas.4
Aquinas, like other medieval Aristotelians, maintained that both active and passive powers were crucial for explaining how causation happens. According to him, causal interactions involve an agent substance which acts upon a patient substance. By its action, the agent communicates a form to the patient. The patient can only undergo the agent’s action in virtue of having a passive potentiality to receive the relevant type of form. Though the role of passive powers in explaining change is well known by Aquinas’s readers, there has been little scholarship on the precise nature of the passive potencies of material substances by which they undergo one another’s action.5 This article will recover Aquinas’s thinking by focusing on three central questions regarding passive potencies: First, what is the basis or source of a material substance’s passive potentialities? Put otherwise, what constituents of material substances explain why they have capabilities for being acted upon? Second, how are a material substance’s passive potencies identified and distinguished from one another? For instance, on what grounds is the potentiality to undergo burning distinguished from the potentiality to undergo heating? Lastly, are a substance’s passive potencies for undergoing action the same as its potencies for existing in determinate ways? For example, is a pot of water’s potentiality for being heated the same as its potentiality for being hot? Or are these two different potentialities? In the three following sections of this article, I consider Aquinas’s views on each of these three questions. Finally, in conclusion, I offer some observations about why Aquinas thought that passive potencies were necessary – in addition to active ones – to explain how material substances could act on and be acted upon by one another.
2 Sources of Passive Potency
In this section we will examine Aquinas’s views on the sources of a material substance’s passive potentialities. We will see which intrinsic components of substances are those in virtue of which they have potentialities to undergo action. Aquinas’s views on this question are intertwined with his hylomorphism. Hylomorphism is the view that material substances are composed of matter and form. Forms are that through which substances exist in determinate ways. For instance, through an inherent form of whiteness, a substance exists as white. Matter is that which receives or is informed by form. We will see that for Aquinas both a substance’s matter and the forms which actualize it give rise to the substance’s passive potentialities.
2.1 Matter as That through Which Material Substances Undergo One Another’s Actions
To understand Aquinas’s views on the role of matter as a source of passive potentiality, it is helpful to begin with a brief overview of his views on form’s role in causal activity. According to Aquinas, forms are not only principles of being and actuality, but also principles of activity.6 For example, the form of heat is both that through which fire is hot and also that through which it heats.7 Aquinas conceives of the action which a material substance performs through its form as a communication of its form to another.8 He writes: “To act is nothing other than to communicate that by which the agent is in act in so far as it is possible.”9 For example, when fire performs the action of heating water it communicates the form of heat to the water. Elsewhere Aquinas writes the following about action: “The form which belongs to a being does not come to be in another except through its action: for the agent makes another like itself in so far as it communicates its form to another.”10 Through their inherent forms, material substances are able to communicate forms of the same kind to other material substances.
Aquinas explicitly claims that substances are not active in virtue of their matter. He writes: “It is manifest that a body cannot act through its whole self since it is composed of matter, which is a being in potency, and of form, which is act: for any being acts in so far as it is in act.”11 Since action involves communicating the principle by which a substance is in act (i.e., that by which it exists in a determinate way) and matter is not a principle of act, it follows that matter is not a principle of action. Matter is rather a principle of passivity.
Texts throughout Aquinas’s corpus reveal that he thought that the complementary nature of form and matter is that which makes it possible for material substances to act on and be acted upon by one another. For causal interactions to occur, material substances must have both an active and a receptive component. Aquinas writes in his De potentia: “There is mutual action in corporeal substances because the matter of one is in potency to the form of the other and vice versa.”12 Similarly, he writes in the Summa theologiae: “The potency for being is from the part of matter, which is a being in potency, but the potency for acting is from the part of form.”13 If material substances were bundles of form (i.e., without any matter), substances would not be able to be acted upon since there would be nothing within a substance which would be susceptible to receiving form. Aquinas writes: “No thing, whatever its degree of materiality, receives anything according to that which is form in it, but only according to that which is material in it … Corporeal things do not receive any impression in virtue of form, but only in virtue of matter.”14 In Aquinas’s view, it is the “fit” between form as that which perfects and matter as that which can be perfected that enables agents to act and patients to suffer. Aquinas writes:
There is a proportion between matter and form because there is an order such that matter is perfected by form, and it is according to a proportionality. For just as form is able to give being, so too matter is able to receive that same being. In this way also the mover and the moved have a proportionality, and also the agent and the patient, so that just as an agent is able to impress some effect, so is the patient able to receive the same.15
The agent can act on a patient because the agent has something by which it can communicate being-in-actuality (form), and the patient has something by which can receive being-in-actuality (matter).
The passages presented in this section make clear that Aquinas held that substances undergo action in virtue of their matter. However, an important question remains about this view: Which type of matter does Aquinas have in mind when he makes these claims? As is well known to scholars of his thought, Aquinas, along with other Aristotelians, distinguishes between different types of matter.16 One type of matter is prime matter, which, in Aquinas’s view, is a principle of pure potency. Prime matter is that which is actualized by a substantial form to compose a material substance of a determinate substantial kind, such as a cat, a human, or a tree. In cases of substantial generation and corruption, prime matter is that which is first under one substantial form and then under another.17 According to Aquinas’s view, prime matter has no actual properties of itself and only exists in so far as it composes a complete material substance.18 In addition to prime matter, Aquinas also acknowledges another notion of matter called “proper matter” (materia propria). For each substantial kind of material substance, there is a determinate type of “proper matter” out of which the substance must be made in order to be the kind of thing that it is. For example, regarding the human being’s proper matter, Aquinas writes: “Since indeed the proper matter of a human is a body mixed, constituted and organized in a certain way, it is absolutely necessary for man to have in himself any given elements, humors and principal organs.”19 A human being cannot be made out of copper or stone. Rather, human beings must be made of certain organic materials and they must have certain organs. These organs and materials are that through which the human being is able to receive the higher perfection of rationality. Proper matter is not devoid of actual qualities as prime matter is. Rather, proper matter is matter which is actualized by both a substantial form and accidental ones.20 The actual qualities of proper matter make it suitable matter for the substance’s higher perfections. The central question of interest for our purposes is whether Aquinas thought that prime matter or proper matter is that by which substances undergo change.
Aquinas’s perspective on this question is revealed in a passage from his Metaphysics commentary. He writes:
The patient undergoes something on account of some principle existing in it, and matter is of this kind. Passive potency is nothing other than the principle for undergoing the action of another. For example, to be burned is an undergoing, and the material principle on account of which something is apt to be burned is the oily or the fatty. Hence the very potency in the combustible thing is as it were passive. Similarly, that which yields itself to touching so that it receives a certain impression, just as wax or something of this kind, in so far as it is of such a kind, is impressionable.21
In the beginning of the passage, Aquinas states that substances undergo action in virtue of their matter or material principle. He then gives several examples to illustrate this point. He says that a substance is combustible on account of being oily or fatty, and substances are impressionable on account of having a certain consistency which yields to touch. These examples make clear that the material element through which substances undergo action is not prime matter, which is devoid of all quality, but rather matter which is under certain forms. Oily or fatty material is matter actualized by certain forms. The specific qualities of oily or fatty matter are that which enables a substance to undergo a determinate type of action, such as burning.
2.2 Qualitative Forms as Disposing Substances to Undergo Action
Aquinas at times emphasizes the role of form in conferring the ability to undergo action. According to Aquinas, in order for a substance to undergo an action it must have a disposition for undergoing it. He writes: “It is necessary that that which is able to undergo something have within itself some disposition which is the cause and principle of such an undergoing, and this principle is called passive potency.”22 ‘Disposition’ is a technical term in Aquinas’s thought. A disposition is an order which a subject has through one of its qualities toward something else. Aquinas writes: “Disposition implies a certain order, as was said. Therefore, someone is not said to be disposed through a quality except with reference to something else.”23 Aquinas identifies various types of dispositions which a substance can have toward something else. One type of disposition is an order of matter toward the reception of a certain form. He writes: “One way is how matter is disposed to the reception of form, just as heat is a disposition for the form of fire.”24 Heat is considered a disposition for fire since a subject which is hot is ordered toward receiving the form of fire. Through heat the subject is prepared to receive this further form.
We saw above that Aquinas claimed that substances do not receive anything in virtue of what is formal in them, but rather only through that which is material.25 While it is indeed the case that only that which is material can receive or be actualized by form, substances must nevertheless be disposed by form in order to receive further forms through their matter.26 Since forms are required to dispose matter to receive further forms, Aquinas at times refers to certain qualitative forms as “potencies.” For instance, he writes: “Dryness is a potency in timbers since according to this they are combustible.”27 This description of a formal quality as potency is consistent with Aquinas’s earlier claims that matter is that by which substances undergo action since dryness, or any other form, is a source of potency in so far as it disposes matter for the reception of form. While matter is that from which a substance’s capacity to be acted upon in general arises, it is through form that the substance has potentialities for undergoing determinate types of action.
3 The Diversification of Passive Potencies
In the previous section, we examined Aquinas’s views about the constituents of material substances through which they undergo one another’s actions. We saw that material substances are able to receive form from another because they have a material element which can take on form. Furthermore, we saw that the formal qualities of material substances likewise play a role in disposing the substance toward the reception of determinate types of forms. Thus, both the material and the formal elements of a material substance give rise to its capacities to undergo actions, i.e., its passive potentialities. In this section, we will examine Aquinas’s views on how passive potentialities are identified and distinguished from one another.
It is useful to begin with some basic points about what potentialities are. In Aquinas’s Aristotelian view, the act-potency distinction expresses a certain sort of relationship between two members of a pair. Potency relates to act as what is imperfect, incomplete, or unfulfilled. Act is the perfection, completion, fulfillment, or manifestation of potency. Aquinas follows Aristotle in claiming that act and potency are best understood through analogies which illustrate the relationship or proportion between them. For example, act relates to potency as the one awake relates to the one who is sleeping, or as the one who is seeing relates to the one with his eyes closed.28
Aquinas maintains that potentialities are identified and diversified by their corresponding actualities.29 For instance, the potentiality for being white is what it is through its order toward the actuality of being white. The potentiality to be white differs from the potentiality to be black through the difference of the actualities to which they are ordered, i.e., whiteness and blackness. The actuality which corresponds to a passive potency is the actual undergoing of an action. For example, the passive potency to be heated is ordered toward the actuality of heating. Since passive potentialities have their reality and identity through their order toward the diverse types of acts which can be undergone, we must know how acts are diversified in order to know how passive potentialities are diversified.
Aquinas claims that the acts corresponding to passive potencies are distinguished from one another by their objects.30 An ‘object’ is a reality which is ordered to or bears upon an act. Aquinas claims that the object of a passive potency’s act is that which initiates the action.31 For example, the act of being heated is a different undergoing from the act of being cooled since being heated arises from an active power to heat and being cooled arises from an active power to cool. An undergoing is an undergoing of a particular kind in virtue of arising from a particular kind of active power. Aquinas claims that, in a sense, correlative active and passive potencies, such as the potency to heat and be heated, comprise just a single potency. He writes: “In a certain way the potencies for acting and for being acted upon are one potency … They are one potency in so far as the order of one to the other is considered; for one is said with respect to the other.”32 For instance, since the potency to heat another can only be actualized if there is something capable of being heated and vice versa, it seems that the potencies for heating and being heated comprise just a single potentiality for the act of heating. Since passive potencies are differentiated by their acts and these acts are in turn differentiated by the active powers which initiate them, there will be as many passive potencies as there are types of active powers.
However, Aquinas notes that not just any difference in the active power which moves a passive potency (i.e., the object) entails a distinct passive potency.33 Differences among agents which are accidental to the nature of the active potency do not entail a distinction of passive potencies.34 Only differences among the very active potencies themselves entail a diversity of passive potencies. For example, water might be heated by an electric stove or by an open flame. Aquinas’s point is that this does not entail that the water has two different passive potencies: one to be heated by a stove and another to be heated by a flame. Both the stove and the flame heat through the same active quality, namely heat. It is accidental to (i.e., outside of the nature of) this quality whether it belongs to a stove or flame. Thus, only one passive potency is required for a patient to undergo acts of heating even if they are produced by different types of agents which possess a power to heat.
It is worth noting that the diversification of passive potentialities differs from the diversification of the forms from which they arise. Given that passive potentialities are identified and diversified in virtue of the act which the patient undergoes (and not the form from which the potentiality arises), it is possible for forms of different species to give rise to passive potentialities which are of the same kind. In various passages, Aquinas discusses the disposition in virtue of which a substance can be burned. Sometimes he identifies this disposition as dryness.35 Yet, other times he identifies it as the “oily” or the “fatty.”36 Though these qualities differ from each other according to their nature, they both give rise to the same passive potency, which is manifested in the same type of undergoing, namely burning. Furthermore, it seems that one and the same qualitative form can be a source of two different types of passive potentiality. For example, through having a waxy consistency, a substance is both bendable and meltable. The potentialities differ, but the form in virtue of which the substance has the potentialities is the same.
In this section we have seen that passive potentialities are identified and diversified in virtue of their actualizations. Their actualizations are, in turn, diversified by the active powers from which they arise. Passive potentialities are not identified or diversified in virtue of the forms from which they arise. As we have seen, specifically different forms can give rise to potentialities of the same kind and a single form can give rise to multiple passive potentialities.
4 Are Passive Potencies for Undergoing Action the Same as Potencies for Existence?
The topic of this final section is the question of how passive potencies relate to another type of potency which Aquinas attributes to material substances, namely potencies for being a certain way. In the context of discussing the metaphysics of change, Aquinas claims that for every determinate way in which a substance can exist in actuality, there is some corresponding potency. For instance, being just and being white and being a human are all ways of existing in actuality. Aquinas thinks that corresponding to each of these there is something which is being ‘potentially white’ or ‘potentially just’ or ‘potentially a man’.37 These potentialities are actualized by form. Aquinas never addresses how these potencies relate to the passive potencies for undergoing an action. Is a substance’s potency for a certain way of being the same as or different from the substance’s passive potency to undergo an action which terminates in that way of being? For example, is water’s potency to be hot the same as its passive potency to be heated? Contemporary scholars have debated quite extensively about Aristotle’s views on this topic.38 Aquinas’s views on this issue are no less difficult to interpret.39 In what follows, I will discuss some of the relevant considerations in favor of identifying vs. distinguishing passive potencies for undergoing action and potencies for being. I will argue that from Aquinas’s principles it follows that these potencies are the same in reality, though they may differ according to concept.
There are several texts in Aquinas’s works which suggest that he regarded a substance’s passive potency to undergo an action as the same as the substance’s potency to take on the form which is the end point of the action. In a De potentia passage in which he discusses the two-fold division of act into form (first act) and operation (second act), he goes on to state that potency is similarly divided in a two-fold manner. He writes:
Potency is similarly two-fold: one is active potency, which corresponds to the act which is operation, and it appears that the name ‘potency’ was first attributed to this one. The other is passive potency, which corresponds to first act, which is form.40
It is important to note what Aquinas does not say in the passage. He does not divide passive potency further into a potency for existing according to a form and a potency for undergoing the action which terminates in that form. He simply divides potency into active and passive potency. Aquinas states that the act which corresponds to passive potency is first act or form. He does not differentiate two separate passive potencies: one which is actualized by a form (i.e., first act) and another which is actualized by the undergoing of an action (i.e., second act). He only refers to a single type of passive potency which is actualized by form.
In another passage in his Summa theologiae, Aquinas likewise contrasts the active potency for acting with the potency for being. He writes: “The potency for being is possessed on account of matter, which is a being in potency. However the potency for acting is possessed on account of form, which is a principle of acting, since any given thing acts in so far as it is in act.”41 We saw above that Aquinas claimed that matter is the principle in virtue of which material substances undergo action, and here he claims that matter is that through which substances have potency for being. So, it seems that perhaps there is just a single type of passive potency in virtue of which substances receive form and in virtue of which they undergo action. This fits with Aquinas’s conception of action as the communication of a form. If undergoing an action is nothing other than receiving a form, it seems that no further potency is required to undergo action beyond the potency to have a form.
However, there are some other texts which support a conflicting perspective. For instance, in Aquinas’s discussion of motion in his commentary on Aristotle’s Physics, he states that a changeable substance which is not yet actually undergoing change is in potency to two acts. He writes:
It must be considered that before something is moved it is in potency to two acts, namely a perfect act, which is the term of motion, and an imperfect act, which is the motion. For example, water before it begins to be heated is in potency to heating and to being hot. While it is being heated, it is reduced to the imperfect act, which is motion; however, it is not yet in perfect act, which is the term of motion, but with respect to this it remains in potency.42
This passage seems to imply that the potency for undergoing the action of a mover is different from the potency for being in the end state of the motion. Aquinas states that while a substance is being heated, its potency to undergo heating is actualized, and yet, it seems to have some other un-actualized potency for the final result of the heating (i.e., being hot to a certain degree). Conversely, even after the source of heating has ceased in its action of heating, the water will still be hot – yet it will no longer actually be undergoing heating. Since undergoing heating in actuality differs from being hot in actuality there must similarly be two different potentialities, one for being hot and one for undergoing heating. As we saw in the previous section, Aquinas maintains that potencies are diversified in accord with their acts. The passive potency to undergo cooling, for example, differs from the passive potency to undergo heating since heating and cooling are different types of act. It would seem that if a substance is in potency to two acts, as the passage above claims, and potencies are individuated by their acts, then the substance must have two potencies. Further on in his Physics commentary Aquinas similarly discusses the case of materials which are in potency to being built into a house. He describes the actuality of materials in so far as they are “buildable” (i.e., in potency to being built) as the very motion of building. He explicitly denies that the act of the materials “as buildable” is the end state of the house. Rather it is the very process of building.43 Since the act of building and the actual house are two different actualities, it would likewise seem that there are two passive potencies: one for being a house and one for undergoing building. Again, potentialities are diversified in terms of their acts.
One thing to keep in mind with regard to this consideration about the “two acts” is that Aquinas maintained that only a certain sort of difference between two actualities is sufficient to diversify the corresponding potencies. In order for different acts to entail different potencies, the acts must differ according to species.44 However, the act which a substance has when it is undergoing an action and the act which it has when it exists according to the end-state of that action are of the same species. For example, when a substance is undergoing heating and when it exists as hot, it is actualized by one and the same act, namely a form of heat. In several texts, Aquinas explicitly claims that the imperfect act which a substance has when it is in motion, e.g. when it is being heated, is of the same species as the act it has at the end of the motion.45 The difference in the act which the substance has when it is being heated vs. existing as hot is not a difference of species. Rather it is a difference in how perfectly the substance is actualized. A substance which is undergoing a motion is imperfectly actualized by the relevant form, and it has an order toward being more perfectly actualized by that form at each successive instant of the motion.46 Motion, for Aquinas, involves a special way of being actualized by a form, rather than a different type of form.47 A substance in motion is actualized in such a way that it remains in potency.48 Since the form which is received when a substance undergoes a motion is the same as the form through which it has a way of being in actuality, it seems that a patient should not require a distinct passive potency to undergo an action in addition to its passive potency to exist according to the relevant form. For instance, since water is actualized by the same form of heat both when it exists as hot and when it is being heated, water should not require two distinct potentialities, one for being hot and another for being heated. Being heated, after all, is just a certain way of being hot, i.e., being hot while retaining a potency toward being continuously hotter.
Though I have argued that according to Aquinas’s principles potencies for being and undergoing action are the same in reality, Aquinas nevertheless thinks such potencies differ conceptually. For example, though the potencies for being hot and undergoing heating are the same in reality, our notion of a potency to be hot differs from our notion of a potency to be heated. To understand what a potentiality for being hot is, we only need to understand what hotness is. However, to understand a potentiality for being heated, the notion of an active power which heats is also required. Aquinas claims that active and passive potencies are relatives, which is to say that they can only be specified and defined in relation to each other.49 The potentiality for being heated is a potentiality for undergoing the action of an active power to heat. The concept of every passive potency includes reference to the power which actualizes it. By contrast, the concept of a potency for being only includes reference to the form which is its act.50 For instance, the potentiality to be hot is defined as a potency for receiving the form of heat, while the potency to undergo heating is defined as a potency to receive the form of heat through an agent’s active power to heat. In reality, however, the potentiality for undergoing heating and being hot are one and the same potentiality.
5 Conclusion
In this article we have seen Aquinas’s views on the sources of material substances’ passive potentialities as well as how such potentialities are identified and diversified. In his view, material substances have the passive potentiality to receive form in virtue of their matter. Yet, the forms which actualize matter also play a role in disposing substances toward the reception of determinate forms. However, it must be emphasized that a given substance’s specific passive potentialities are not identified and diversified through the inherent forms from which they arise. Rather, passive potentialities are identified and diversified through their corresponding acts. Distinct types of forms can give rise to the same type of passive potency, and one form can give rise to multiple distinct passive potencies.
From the views of Aquinas which we have seen in this article, it is possible to draw some general conclusions about why, in addition to active potentialities, passive potentialities are required for causal interactions between material substances. In Aquinas’s view, efficient causation involves a communication of form from the agent to the patient. The agent communicates a form which the patient receives. Thus, agents and patients contribute to causal interactions in diverse ways. Since causation also involves reception of form, a different sort of capacity from active capacity is required. Active potentialities cannot alone suffice since they are ordered toward production, rather than reception. Aquinas’s view that passive potency arises from a substance’s material principles, while active potencies are aligned with form, highlights that it is the hylomorphic composition of material substances that enables them to causally interact. Through being composed of matter and form, material substances have both an active and a receptive potentiality. Though active potencies and passive potencies belong to diverse substances, they fit together on account of the complementarity of matter and form. Form is that which perfects, and matter is that which can be perfected by form. Thus, it is on account of their hylomorphic structure that material substances have two corresponding types of potentialities, namely active and passive, both of which are essential for causal interactions.
References
Authors before ca. 1500
Thomas Aquinas, Commentaria in octo libros Physicorum Aristotelis, eds. Fratres Praedicatores. Opera omnia 2 (Rome, 1884).
Thomas Aquinas, De principiis naturae, eds. Fratres Praedicatores. Opera omnia 43 (Rome, 1976), 39–47.
Thomas Aquinas, In duodecim libros Metaphysicorum Aristotelis expositio, eds. M.-R. Cathala and R. M. Spiazzi (Turin, 1964).
Thomas Aquinas, Liber de veritate catholicae fidei contra errores infidelium seu Summa contra Gentiles, eds. C. Pera, P. Marc and P. Caramello (Turin, 1961).
Thomas Aquinas, Quaestiones disputatae de anima, ed. B.-C. Bazán. Opera omnia 24/1 (Rome, 1996).
Thomas Aquinas, Quaestiones disputatae de potentia, ed. P. M. Pession. In Thomas Aquinas, Quaestiones disputatae 2 , eds. P. Bazzi, M. Calcaterra, T. S. Centi, E. Odetto and P. M. Pession (Turin, 1965), 7–276.
Thomas Aquinas, Quaestiones disputatae de veritate, 2/1: Qq. 8–12, eds. Fratres Praedicatores. Opera omnia 22 (Rome, 1970).
Thomas Aquinas, Quaestiones disputatae de virtutibus, ed. E. Odetto. In Thomas Aquinas, Quaestiones disputatae 2, eds. P. Bazzi, M. Calcaterra, T. S. Centi, E. Odetto and P. M. Pession (Turin, 1965), 707–828.
Thomas Aquinas, Scriptum super primum librum Sententiarum, ed. R. P. Mandonnet (Paris, 1929).
Thomas Aquinas, Scriptum super secundum librum Sententiarum, ed. R. P. Mandonnet (Paris, 1929).
Thomas Aquinas, Scriptum super tertio libro Sententiarum, ed. M. F. Moos (Paris, 1933).
Thomas Aquinas, Summa theologiae I, qq. 50–119, eds. Fratres Praedicatores. Opera omnia 5 (Rome, 1889).
Thomas Aquinas, Summa theologiae I–II, qq. 1–70, eds. Fratres Praedicatores. Opera omnia 6 (Rome, 1891).
Thomas Aquinas, Summa theologiae III, qq. 1–59, eds. Fratres Praedicatores. Opera omnia 11 (Rome, 1903).
Authors after ca. 1500
Boland, V. “Aquinas and Simplicius on Dispositions—A Question in Fundamental Moral Theory.” New Blackfriars 82 (2001), 467–478.
Brower, J. E. Aquinas’s Ontology of the Material World: Change, Hylomorphism, and Material Objects (Oxford, 2014).
Damschen, G., R. Schnepf and K. R. Stüber, eds. Debating Dispositions: Issues in Metaphysics, Epistemology and Philosophy of Mind (Berlin, 2009).
Engelhard, K., and M. Quante, eds. Handbook of Potentiality (Dordrecht, 2018).
Fisher, K. “Thomas Aquinas on Hylomorphism and the In-Act Principle.” British Journal for the History of Philosophy, 25 (2017), 1053–1072.
Fitzpatrick, A. Thomas Aquinas on Bodily Identity (Oxford, 2017).
Groff, R., and J. Greco, eds. Powers and Capacities in Philosophy: The New Aristotelianism (New York, 2013).
Hansson Wahlberg, T. “Active and Passive Powers—Do Causal Interactions Require Both?” Philosophia 47 (2019), 1603–1612.
Heinaman, R. “Is Aristotle’s Definition of Change Circular?” Apeiron 27 (1994), 25–37.
Jacobs, J. D., ed. Causal Powers (Oxford, 2017).
Johansen, T. K. The Powers of Aristotle’s Soul (Oxford, 2012).
Kahm, N. Aquinas on Emotion’s Participation in Reason (Washington, DC, 2019).
Kent, M. Prime Matter according to St. Thomas, Dissertation (Fordham University, 2006).
Löwe, C. L. “Mind over Matter: Aquinas’s Transformation of Aristotle’s Definition of ‘Change’.” Archives d’histoire doctrinale et littéraire du Moyen Âge 82 (2015), 45–68.
Marmodoro, A., ed. The Metaphysics of Powers: Their Grounding and Their Manifestations (New York, 2010).
Meehan, F. X. Efficient Causality in Aristotle and St. Thomas (Washington, DC, 1940).
Mumford, S. “Powers, Dispositions, Properties or a Causal Realist Manifesto.” In Revitalizing Causality: Realism about Causality in Philosophy and Social Science, ed. R. Groff (New York, 2008), 139–151.
Pasnau, R. Thomas Aquinas on Human Nature: A Philosophical Study of Summa Theologiae 1a 75–89 (Cambridge, 2002).
Rota, M. W. “Causation.” In The Oxford Handbook of Aquinas, eds. B. Davies and E. Stump (Oxford, 2012), 104–114.
Wippel, J. F. The Metaphysical Thought of Thomas Aquinas: From Finite Being to Uncreated Being (Washington, DC, 2000).
I am grateful to Can Löwe and the anonymous referees for Vivarium for helpful comments on earlier drafts of this paper. I would also like to thank Jeff Brower, David Cory, Therese Scarpelli Cory, Scott MacDonald, and Jake Tuttle for helpful comments and discussion of the ideas in this paper.
Within the past decade, in addition to several articles and monographs on causal powers, the following edited volumes have appeared in contemporary philosophy: Damschen, Schnepf and Stüber, eds. Debating Dispositions; Engelhard and Quante, eds. Handbook of Potentiality; Groff and Greco, eds. Powers and Capacities; Jacobs, ed. Causal Powers; Marmodoro, ed. The Metaphysics of Powers.
Hansson Wahlberg, “Active and Passive Powers.”
Mumford, “Powers,” 140, writes: “Being able to do something and being able to have something done are both powers of an object, a metaphysical par.”
This article focuses on material substances’ passive potentialities for undergoing the natural actions of other material substances. It should be noted, however, that Aquinas maintained that there were also other types of passive potentialities. He attributed to every created substance an “obediential potency” for undergoing God’s actions. See, for instance, Thomas Aquinas, Scriptum super III Sent., d. 2, q. 1, a. 1, q. 3, 54. Furthermore, he thought that intellectual beings had a passive potentiality for being actualized by intelligible forms (i.e., the passive or possible intellect). On the human passive intellect, see for example Summa theologiae I, q. 79, a. 2, 259–260. These other types of potentialities fall outside of the scope of this article.
Important works on Aquinas’s views of efficient causation have noted the role of passive powers in causal interactions without offering much analysis of what they are in themselves. See for example Rota, “Causation,” and Meehan, Efficient Causality. There have been more detailed discussions of the passive powers of the human soul. See for example Pasnau, Thomas Aquinas on Human Nature. Though this work primarily focuses on human capacities, it includes illuminating points relevant to all capacities. See especially 148–149, where Pasnau discusses development in Aquinas’s views on how to distinguish active and passive powers. Another recent work on the powers of the human soul which also includes a brief overview of the definition and individuation of passive powers in general is Kahm, Aquinas, 66–70. The present article differs from these discussions in so far as it focuses primarily on the passive powers of non-human material substances.
See for instance Thomas Aquinas, Summa theologiae III, q. 13, a. 1, 171a: “Potentia autem activa cuiuslibet rei sequitur formam ipsius, quae est principium agendi.”
For a recent discussion of Aquinas’s view that substances act in so far as they are in act through their forms, see Fisher, “Thomas Aquinas on Hylomorphism.” Aquinas links forms with activity because forms are principles of actualization and perfection and are, therefore, good. Following his neo-Platonic sources, he conceives of the good as self-diffusive. See for instance Thomas Aquinas, Summa contra Gentiles I, c. 37, t. 2–3, 47, n. 307. Thus, given that forms are self-diffusive goods, they are by their nature self-diffusive or communicable. See for instance Thomas Aquinas, Scriptum super I Sent., d. 4, q. 1, a.1, 132: “Communicatio enim consequitur rationem actus: unde omnis forma, quantum est de se, communicabilis est.” See also De potentia, q. 2, a. 1, 25.
It should be noted that Aquinas explicitly denies that some entity passes over from the agent into the patient in efficient causation. See for instance Thomas Aquinas, Summa contra Gentiles III, c. 69, 98, n. 2458. The claim that the agent communicates its form to the patient is about the type of change which the agent causes – not the mechanism by which the agent causes change.
Thomas Aquinas, De potentia, q. 2, a. 1, 25a: “Unde unumquodque agens agit secundum quod in actu est. Agere vero nihil aliud est quam communicare illud per quod agens est actu, secundum quod est possibile.” English translations are my own.
Thomas Aquinas, Summa contra Gentiles III, c. 52, 71, n. 2292: “Forma alicuius propria non fit alterius nisi eo agente: agens enim facit sibi simile inquantum formam suam alteri communicat.”
Thomas Aquinas, Summa contra Gentiles III, c. 69, 98, n. 2496: “Manifestum est enim quod corpus non potest agere se toto, cum sit compositum ex materia, quae est ens in potentia, et ex forma, quae est actus: agit enim unumquodque secundum quod est actu.” See also Scriptum super II Sent., d. 30, q. 2, a. 2, 791: “Virtus activa non est ex parte materiae, sed magis ex parte formalis principii.”
Thomas Aquinas, De potentia, q. 3, a. 7, 57b: “Et inde sequitur quod est mutua actio in substantiis corporalibus, cum [in] materia unius sit in potentia forma alterius, et e converso.” See also In Phys. III, lect. 2, 106, n. 6: “Et quia omnia corpora naturalia inferiora communicant in materia, ideo in unoquoque est potentia ad id quod est actu in altero: et ideo in omnibus talibus aliquid simul agit et patitur, et movet et movetur.”
Thomas Aquinas, Summa theologiae I–II, q. 55, a. 2, 351a: “Sed potentia ad esse se tenet ex parte materiae, quae est ens in potentia; potentia autem ad agere se tenet ex parte formae.”
Thomas Aquinas, De veritate, q. 9, a. 1, ad 12, 282a: “Ad duodecimum dicendum quod nulla res quantumcumque materialis recipit aliquid secundum id quod est formale in ipsa, sed solum secundum id quod est materiale in ea … res corporales non recipiunt aliquam impressionem ex parte formae, sed ex parte materiae.”
Thomas Aquinas, Scriptum super III Sent., d. 1, q. 1, a. 1, ad 3, 10: “Sicut dicimus esse proportionem inter materiam et formam, quia materia se habet in ordine ut perficiatur per formam, et hoc secundum proportionalitatem quamdam. Quia sicut forma potest dare esse, ita materia potest recipere idem esse. Et hoc modo etiam movens et motum debent esse proportionalia, et agens et patiens, ut scilicet sicut agens potest imprimere aliquem effectum, ita patiens possit recipere eumdem.”
For an overview of the different types of matter Aquinas recognizes see Kent, Prime Matter. For another recent discussion of Aquinas’s views on matter and hylomorphism see Brower, Aquinas’s Ontology.
Thomas Aquinas, In Phys. I, lect. 13, 46b, n. 9: “Sic enim cognoscimus quod lignum est aliquid praeter formam scamni et lecti, quia quandoque est sub una forma, quandoque sub alia. Cum igitur videamus hoc quod est aer quandoque fieri aquam, oportet dicere quod aliquid existens sub forma aeris, quandoque sit sub forma aquae: et sic illud est aliquid praeter formam aquae et praeter formam aeris, sicut lignum est aliquid praeter formam scamni et praeter formam lecti. Quod igitur sic se habet ad ipsas substantias naturales, sicut se habet aes ad statuam et lignum ad lectum, et quodlibet materiale et informe ad formam, hoc dicimus esse materiam primam.”
Thomas Aquinas, In Phys. I, lect. 14, 50b, n. 8: “Materia, quae est ens in potentia, est id ex quo fit aliquid per se: haec est enim quae intrat substantiam rei factae.” In Phys. I, lect. 15, 54a–b, n. 11: “Sed primum quod subiicitur in generatione est materia: hoc enim dicimus materiam, primum subiectum ex quo aliquid fit per se et non secundum accidens, et inest rei iam factae.” See also In Metaph. XII, lect. 2, 571b, n. 2437.
Thomas Aquinas, Summa contra Gentiles II, c. 30, 142, n. 1074: “Quia enim materia propria hominis est corpus commixtum et complexionatum et organizatum, necessarium est absolute hominem quodlibet elementorum et humorum et organorum principalium in se habere.” For literature see Fitzpatrick, Thomas Aquinas, 29–30.
Aquinas maintained that each material substance had just one substantial form. The one substantial form was responsible for actualizing both the lower material qualities of the substance, as well as its higher qualities. For example, through the same substantial form, a human is both a fleshy, organic body and rational. See Wippel, The Metaphysical Thought of Thomas Aquinas, 237–251.
Thomas Aquinas, In Metaph. IX, lect. 1, 425b–426a, n. 1782: “Patiens patitur propter aliquod principium in ipso existens, et huiusmodi est materia. Potentia autem passiva nihil aliud est quam principium patiendi ab alio. Sicut comburi quoddam pati est; et principium materiale propter quod aliquid est aptum combustioni, est pingue vel crassum. Unde ipsa potentia est in combustibili quasi passiva. Et similiter illud quod sic cedit tangenti ut impressionem quamdam recipiat, sicut cera vel aliquid huiusmodi, inquantum tale est frangibile.”
Thomas Aquinas, In Metaph. V, lect. 14, 257b, n. 963: “Oportet autem illud, quod est possibile ad aliquid patiendum, habere in se quamdam dispositionem, quae sit causa et principium talis passionis; et illud principium vocatur potentia passiva.”
Thomas Aquinas, Summa theologiae I–II, q. 49, a. 2, ad 1, 311a: “Dispositio ordinem quendam importat, ut dictum est. Unde non dicitur aliquis disponi per qualitatem, nisi in ordine ad aliquid.” For literature see Boland, “Aquinas and Simplicius.”
Thomas Aquinas, De virtutibus, 710a: “Dispositio dicitur tribus modis. Uno modo per quam materia disponitur ad formae receptionem, sicut calor est dispositio ad formam ignis.”
See note 14.
For a text in which Aquinas explicitly claims that accidents are received in virtue of other accidents, see Summa theologiae I, q. 77, a. 7 ad 2, 247b–248a: “Accidens per se non potest esse subiectum accidentis; sed unum accidens per prius recipitur in substantia quam aliud, sicut quantitas quam qualitas. Et hoc modo unum accidens dicitur esse subiectum alterius, ut superficies coloris, inquantum substantia uno accidente mediante recipit aliud.”
Thomas Aquinas, Quaestiones de anima, q. 12, 108: “Siccum est potentia in lignis, quia secundum hoc sunt combustibilia.”
See for instance Thomas Aquinas, In Metaph. IX, lect. 5, 437b, nn. 1826–1827.
See for instance Thomas Aquinas, Summa theologiae I, q. 77, a. 3, 241a: “Oportet quod ratio potentiae diversificetur, ut diversificatur ratio actus. Ratio autem actus diversificatur secundum diversam rationem obiecti. Omnis enim actio vel est potentiae activae, vel passivae.” For a discussion of Aquinas’s views on how objects are prior to acts, see Johansen, The Powers, 97–100. Johansen offers some critique of Aquinas’s views. According to Aquinas, the objects of passive powers are prior to the acts of such powers in so far as they are efficient causes of such acts. Johansen claims that the more significant priority of objects over acts is in terms of formal causality.
See previous note.
Thomas Aquinas, Summa theologiae I, q. 77, a. 3, 241a: “Obiectum autem comparatur ad actum potentiae passivae, sicut principium et causa movens; color enim inquantum movet visum, est principium visionis.”
Thomas Aquinas, In Metaph. IX, lect. 1, 425b, n. 1781: “Potentia faciendi et patiendi est quodammodo una potentia … Una quidem est, si consideretur ordo unius ad aliam; una enim dicitur per respectum ad alteram.”
See Thomas Aquinas, Summa theologiae I, q. 77, a. 3, 241–242.
See Thomas Aquinas, Summa theologiae I, q. 77, a. 3, 241–242.
See for instance the text quoted in n. 27 above.
See for instance the text quoted in n. 21 above.
Thomas Aquinas, De principiis naturae, 399–16: “Ad utrumque esse est aliquid in potentia. Aliquid enim est in potentia ut sit homo, ut sperma et sanguis menstruus; aliquid est in potentia ut sit album, ut homo. Tam illud quod est in potentia ad esse substantiale quam illud quod est in potentia ad esse accidentale potest dici materia, sicut sperma hominis et homo albedinis.”
For a summary of some of the positions see Heinaman, “Is Aristotle’s Definition of Change Circular?”
The only discussion of Aquinas’s views which I am aware of is Löwe, “Mind over Matter.” Löwe argues (49–57) that Aquinas distinguished the potency to be a certain way from the potency to the change which terminates in that way of being. In this section, I argue that according to Aquinas’s principles these potentialities are one in reality and only differ according to concept.
Thomas Aquinas, De potentia, q. 1, a. 1, 9a: “Unde et similiter duplex est potentia: una activa cui respondet actus, qui est operatio; et huic primo nomen potentiae videtur fuisse attributum: alia est potentia passiva, cui respondet actus primus, qui est forma.”
Thomas Aquinas, Summa theologiae I–II, q. 55, a. 2, 351a: “Sed potentia ad esse se tenet ex parte materiae, quae est ens in potentia; potentia autem ad agere se tenet ex parte formae, quae est principium agendi, eo quod unumquodque agit inquantum est actu.”
Thomas Aquinas, In Phys. III, lect. 2, 106a, n. 5: “Considerandum est enim quod antequam aliquid moveatur, est in potentia ad duos actus, scilicet ad actum perfectum, qui est terminus motus, et ad actum imperfectum, qui est motus: sicut aqua antequam incipiat calefieri est in potentia ad calefieri et ad calidum esse; cum autem calefit, reducitur in actum imperfectum, qui est motus; nondum autem in actum perfectum, qui est terminus motus, sed adhuc respectu ipsius remanet in potentia.”
Thomas Aquinas, In Phys. III, lect. 3, 107b–108a, n. 2: “Hoc autem est vel domus vel aedificatio. Sed domus non est actus aedificabilis inquantum est aedificabile, quia aedificabile inquantum huiusmodi reducitur in actum cum aedificatur; cum autem iam domus est, non aedificatur. Relinquitur igitur quod aedificatio sit actus aedificabilis inquantum huiusmodi. Aedificatio autem est quidam motus. Motus igitur est actus existentis in potentia inquantum huiusmodi. Et eadem ratio est de aliis motibus.”
See for instance Thomas Aquinas, Summa theologiae I, q. 77, a. 3, 241–242.
See for instance Thomas Aquinas, In Phys. V, lect. 3, 235b, n. 2: “Qualiter autem motus sit in istis generibus, et qualiter pertineat motus ad praedicamentum actionis et passionis, in tertio dictum est. Unde nunc breviter dicere sufficiat quod quilibet motus est in eodem genere cum suo termino, non quidem ita quod motus qui est ad qualitatem sit species qualitatis, sed per reductionem. Sicut enim potentia reducitur ad genus actus, propter hoc quod omne genus dividitur per potentiam et actum, ita oportet quod motus, qui est actus imperfectus, reducatur ad genus actus perfecti.”
Thomas Aquinas, In Phys. III, lect. 2, 105a, n. 3: “Cum enim aqua est solum in potentia calida, nondum movetur; cum vero est iam calefacta, terminatus est motus calefactionis; cum vero iam participat aliquid de calore sed imperfecte, tunc movetur ad calorem; nam quod calefit, paulatim participat calorem magis ac magis. Ipse igitur actus imperfectus caloris in calefactibili existens, est motus, non quidem secundum id quod actu tantum est, sed secundum quod iam in actu existens habet ordinem in ulteriorem actum; quia si tolleretur ordo ad ulteriorem actum, ipse actus quantumcumque imperfectus, esset terminus motus et non motus, sicut accidit cum aliquid semiplene calefit. Ordo autem ad ulteriorem actum competit existenti in potentia ad ipsum.”
On what motion is in external reality, see his In Phys. III, lect. 5, 115a–b, n. 17.
Thomas Aquinas, In Phys. III, lect. 3, 108a, n. 2: “Motus igitur est actus existentis in potentia inquantum huiusmodi.”
Thomas Aquinas, In Metaph. V, lect. 17, 266a, n. 1002. On what relatives are, see Summa theologiae III, q. 35, a. 5, ob. 3, 356a: “Unum relativorum ponitur in definitione alterius; ex quo patet quod unum relativorum specificatur ex alio.”
See note 37 above.