(PDF) Response to interlocutors

Asian Journal of Philosophy (2026) 5:1 https://doi.org/10.1007/s44204-025-00361-0 BOOK SYMPOSIUM Response to interlocutors James Dominic Rooney1 Received: 14 October 2025 / Accepted: 18 November 2025 © The Author(s) 2025 Abstract Contemporary debates about the metaphysics of material composition occur within the framework set by the Special Composition Question, as proposed famously by Peter van Inwagen. This question asks what one must do, what conditions must be satisfied, for some things to compose one object as proper parts. Hylomorphism is a theory that has regained prominence in contemporary metaphysics, explaining the unity of composite material objects by appealing to a special metaphysical part of those objects: structure or form. My book defends hylomorphism as a meaningful and significant answer to questions about the composition of material objects. Specifically, I propose that, if it is false that substances can have other substances as parts, hylomorphism can be shown not only to be a plausible theory but that all consistent accounts of restricted composition can be shown to be hylomorphist. After introducing and summarizing the trajectory of the book, I turn to reviewing and responding to objections from my interlocutors for this symposium. Keywords Material composition · Parthood · Hylomorphism · Confucianism · Structure 1 The controverted points The commentators had problems, chiefly, with the case that I made against the coherence of hylomorphism incorporating the possibility of substances composing other substances as parts, i.e., the Substance Part Principle or SPP. Another major problem concerns the argument that all advocates of restricted composition who reject the SPP are thereby committed to a functional version of hylomorphism. I will briefly present my case for both conclusions before turning to each commentator’s objections in turn. Restricted views of composition reject that every set of two or more things counts as a composite material object. Rather, such accounts are motivated by the intuition * James Dominic Rooney

1 Hong Kong Baptist University, Hong Kong, Hong Kong Vol.:(0123456789) 1 Page 2 of 24 Asian Journal of Philosophy (2026) 5:1 that not everything that might be grouped together or otherwise related counts as a genuine material object. To this end, it is a crucial or central explanatory aim of the metaphysical project of restricted composition that such accounts (if they aim to be explanatory) will identify criteria, and explain what it is in virtue of which, a given set of objects—the genuine material composites—are distinct from the non-genuine or pseudo-objects. The structural hylomorphist identifies form as that in virtue of which some xs compose a y, and therefore form is likewise what explains why something counts as a “genuine” material composite. Being related in just any way should not count as having a form; otherwise, the theory would not be explanatory in restricting the class of material objects. It would be more permissive than mereological universalism. In chapter 5, I argue that, if material composition is understood as restricted, composition should not be a simply external relation, true in virtue of no intrinsic facts about the xs or the ys that compose each other, but true in virtue of something else. I gave different scenarios on which, as long as those factors necessitating composition facts were mind-independent, it would still be the case that the xs and ys would fall under such sortals that are relevant to material composition in virtue of their intrinsic properties, even if they did not need to exemplify a common property to fall under that sortal. I therefore propose a plausible explanatory constraint on restricted composition: “a claim about composition facts being necessitated by something is also required to differentiate the thesis that composition is restricted from either mereological nihilism or universalism. A view on which composition facts are determined in no way by the world, or any object in it, but only by my conceptual schemes or the way I classify the material objects would similarly undermine the distinction between restricted views of composition and those on which composition does not occur” (Rooney, 2022: 135–136). I also argue that there would likewise be a problem if it were an entirely contingent matter whether those properties led to falling under that sortal—if there were not a necessary relation obtaining internally among what is getting composed into a whole (i.e., in terms of the identities of the entities in question), then the composite entities would differ in no important way from the non-composite ones. Further, I argue that proponents of restricted composition ought to reject possibilities like the following: two duplicate possible worlds with the candidate parts and wholes, in which none of the non-mereological facts about these objects varied, but that those worlds differed in terms of the mereological facts (136). If this kind of possibility obtained, it could even be the case that composition could potentially occur without the existence of any material entities at all, as composition facts seem unrelated to the existence and identity of those objects (134–135). Proponents of restricted composition then ought not to hold that it is entirely arbitrary which entities fall under a sortal, in virtue of no intrinsic properties of the parts and wholes, as then it would be difficult to distinguish their view from that of universalists—whether a given set of entities composes an object would not be in any way mind-independent, and the composite objects and their parts (genuine material objects) would not differ in any important way from those that did not compose anything. There would then need to be a necessary relation such that, necessarily, having a given form entails the truth of facts about the composition of those entities, such Asian Journal of Philosophy (2026) 5:1 Page 3 of 24 1 that they fall under a given kind. Likewise, having a form entails falling necessarily under the higher genus of “genuine material composite object.” But importantly: whether some given entities compose a whole cannot be a necessary matter. That is, it should not be the case that for any x, x necessarily composes y. If the xs always compose a y necessarily, whenever the xs exist, this would seem to end up either indistinguishable from mereological universalism or, more plausibly, would terminate in a “brute fact” account where there is a disjunctive list of those entities that compose another necessarily, without any explanation of the way that they relate. Consequently, the proponent of restricted composition must simultaneously deny that all material (entities which are potentially) parts necessarily compose an object simply in virtue of existing, while affirming that intrinsic properties of those parts explain the facts when they do compose the wholes they do. These explanatory constraints are in the background when I evaluate the coherence of SPP (see Rooney, 2022: 40). Accounts of composition like those of the Neo-Aristotelian structural hylomorphists Koslicki and Jaworski hold that there are intrinsic properties of the material xs, in virtue of which those entities fall under a given kind when they compose a y—the form of those parts. And these views also hold the principle that genuine material composite wholes can compose other genuine material composite wholes as proper parts, without ceasing to be the wholes they are. Yet, we need to clarify this thesis, because SPP would be insufficiently characterized if it simply said that substances can become parts of wholes, since this would allow those substances to cease to be substances when they become parts, which is precisely what SPP affirmers want to deny. We need a stronger characterization that substances are “the same” whether they compose any whole or not. But the view would be uninteresting if it said that any x which becomes a part of a whole y is an x, and x = x whether x composes any y. Consequently, I propose that SPP should be interpreted as holding that substances remain the same kind of thing, whether they belong to a whole or not. Individuals which are contingently proper parts would need their individual identity fixed independently of their composition of wholes. Whatever those facts about identity are, they come apart from facts regarding their composition of other entities. SPP thus is best put as the view, briefly, that x coming to compose a whole does not entail a change in x’s kind membership, or their essence. But there are two ways to understand kind membership: belonging to a kind in virtue of satisfying a criterion implicit in the kind itself, rather than in virtue of every member having a common feature or belonging to that kind in virtue of satisfying a criterion of kind membership by exemplifying a common feature. (Given the two ways of understanding kind membership, then, we could understand individual essences or identities in two different ways, understanding each kind to be exemplified by one individual.) SPP entails that material composition does not necessarily affect whether a given x exemplifies the intrinsic or extrinsic properties that are necessary for kind membership (see Rooney, 2022: 37–38). What I then argue is that these claims made by SPP end up entailing results incompatible with maintaining the overall explanatory unity of the account of restricted composition. Here I admit that in the original presentation, my logic was not as clear as it could have been. Unhelpfully, in presenting my overall criticism 1 Page 4 of 24 Asian Journal of Philosophy (2026) 5:1 of SPP by means of criticizing views of structural hylomorphists, it was easy to confuse the latter for the former or think that in criticizing SPP I was criticizing a relational account of structure. My criticisms can be summarized as involving two distinct moves, at two dialectical levels, which I will try to distinguish more clearly in what follows. My overall proposal regarding SPP is parallel to an argument advanced in a recent paper by Masterman, who argues that nihilists who repudiate ontology altogether end up necessarily failing to preserve the explanatory unity of our ordinary claims, in virtue of trying to meet the explanatory requirements of their theory (Masterman, 2025). My particular problem with SPP as held by structural hylomorphists (Fine, Koslicki, Jaworski) is that structures end up being external relations among their relata, and that this generates an infinite regress unless those relations are appropriately grounded. The point here is to illustrate by means of these concrete hylomorphic theories that it is not so much their views about structure that generate the problem, but SPP. So, after discussing those proposals, I move back to the overall proposal and argue that the way SPP necessitates making parts inessential to the wholes they compose would end up conflicting with the overall explanatory unity of an account of restricted composition, for this reason: whatever necessitates the truths about the composition facts ought to lie in the things themselves, and specifically such truths regarding why a given set of parts composes a whole ought therefore to be necessitated in virtue of an internal or essential relation among those parts and the whole. But this is precisely what SPP prevents. It cannot be essential to a particular part that it composes a particular whole, otherwise that part would not be the substance it is “whether or not it composes that whole.” So, SPP makes it impossible for an internal relation among the parts of any given composite material object to be grounded in intrinsic and essential properties of the parts. And this generates an infinite regress that is in principle insoluble unless SPP (or restricted composition) is jettisoned. The latter part of the book argues that coherent accounts of meaningfully restricted composition will all be versions of hylomorphism. Such accounts will posit that there is a particular property that obtains between particular parts and wholes, in virtue of which parts constitute the wholes they do, and that relation has an essential identity independent of the members, although it exists contingently whenever those members exist. This fits the functional characterization of “substantial form” I provided I the book, where a substantial form is “[1] a particular that characterizes all of the things that compose that whole; [2] a particular essentially such that, when it characterizes the parts, those parts compose that particular whole (rather than any whole of that kind); and [3] a particular which is not identical with the whole or any of the material parts” (Rooney, 2022: 160). If SPP is rejected, and meaningful restrictions on composition are the explanatory aim of our account of material composition, then whatever accounts for the unity of material parts cannot be other than an (mind-independent) intrinsic property, common to the parts and wholes that form material composites. What I do to this end is rule out various possibilities on which such properties are mind-dependent (discussed in connection with Fine), or external facts unconnected with intrinsic properties of the particular parts, or universals standing in relations Asian Journal of Philosophy (2026) 5:1 Page 5 of 24 1 rather than tropes (discussed in the fourth chapter by illustration with Zhu Xi), or identity relations (“composition as identity” and Priest’s dialethic vision of material composition). In short, I show broadly that modal recombination-type considerations will require meaningful restrictions on composition to involve mind-independent facts about composition, that the contingency of composition facts, since it does not reduce to identity facts about which parts and wholes exist, would need to vary with facts regarding the existence and identities of particularized properties that inhere in the parts and wholes but are identical with neither, and that these facts about composition are not simply reducible to various identity relations obtaining among the parts and wholes. At each step, then, I am showing by reductio that whatever it is in virtue of which the xs compose a whole cannot be one of two exhaustive options (mind-dependent, etc.). The conclusion is then to identify that any account of restricted composition, to be both meaningful and coherent, needs to have entities that play this functional role, such as “lives” play in Peter van Inwagen’s account of composition. All such theories, I suggest, can be counted as functionally equivalent to hylomorphism, since they involve an entity that functions like a substantial form. 2 Michele Paolini Paoletti Michele Paolini Paoletti helpfully rephrases my dilemma for proponents of SPP (Paoletti 2–3). The dilemma begins with a question: if A is a composite, and B, C, D are its integral parts, and S is its structure/form, do the mere existence of B, C, D and S necessitate the existence of A? He takes the difference between my position and structural hylomorphists to be whether the existence of A consists in, or is at least necessitated by, the holding of S among B, C, and D—as structuralists hold— or the existence of A is identical with S holding among B, C, and D—as he thinks I hold. He then iterates a further higher-level question: “is the holding of S among B, C and D something that obtains by necessity or contingently (among B, C and D)?” If S were to hold merely contingently among B, C, and D, we would seem to get an infinite regress, as we would need a further entity (e.g., S*) and could generate the problem at a further remove (e.g., does S* necessarily hold given S, B, C, and D?). The buck stops somewhere. So, we ought to assume that S holds necessarily. But then we ought to answer whether S holding among B, C, and D is necessitated by the existence of [1] S itself; [2] S plus the existence of B, C, D and/or the existence of A. Paoletti proposes that hylomorphists ought to reject [2]. If [2] is true, we can raise a further question: why is the holding of S among B, C, and D necessitated by the existence of B, C, and D and/or by the existence of A? Paoletti thinks no solution to this dilemma is forthcoming. As he notes, there are several options regarding truths about which entities are essential to other entities that would be potential ways to resolve this worry: e.g., maybe S is essential to A, or S is essential to B, C, and D, and so forth. But he thinks an infinite regress arises, whatever way we deal with this problem, since the requisite essential truths all would be relational. For example, it is essential to D that D stands in S to B and C when B and C exist, because there are essential truths about D that D is distinct from 1 Page 6 of 24 Asian Journal of Philosophy (2026) 5:1 S, B, and C, and these truths hold of D because of other essential truths about D being essentially distinct from S, B, and C, and also distinct from the distinction relation among D, S, B, and, C, and so on, ad infinitum. Or, one would need to divine D into components of its essence, one which essentially unifies and the other that essentially distinguishes D from the other items. But then one needs further entities to distinguish those elements from each other, and so on. Another regress that can be repeated, in principle, with other candidate essential truths, and would not require assumptions about S being a relation or assuming there are essential relations, but only that there are essential relational truths about D, B, C, and/or A. Paoletti argues that rejecting SPP is neither necessary nor sufficient to resolve this dilemma. He notes that, although the “material components are essentially dependent upon one another and/or upon the material substance they turn out to compose,” (Paoletti 6) we can still raise the same question regarding the troublesome essential relational truths that hold among these items. So, Paoletti concludes, we ought to reject that structures are wholly internal relations holding among these relata necessarily whenever the relata exist. Paoletti suggests that accepting [1], on which the “the holding of S among B, C and D is necessitated by the existence of S itself [while it also being the case that] the existence of B, C and D does not necessitate the holding of S among them” (Paoletti 6), would resolve the problem. Specifically, Paoletti suggests that structures are “a relational mode, i.e., a particular relation that depends for its essence and its continued existence upon the very entities among which it holds” (Paoletti 6). Consequently, S necessarily holds among B, C, and D whenever S exists “just because it depends for its essence and continued existence also upon the latter” (Paoletti 6). And Paoletti argues that we cannot similarly appeal to what is essential to the material objects in questions; “The same sort of solution cannot be adopted when it comes to B, C, D and A. For B, C, D and A need not be relational modes. Therefore, the troublesome essential relational truths that give rise to the second regress cannot be dispensed with through internal dependence relations” (Paoletti 7). That is, since material parts are not relational, it cannot be essential to what they are that they relate to another as parts. Only relational beings, like modes, could be that sort of thing essentially. Paoletti misses that my dilemma was not a dilemma for those who think that structures are relational modes but for proponents of SPP. Paoletti therefore misses some aspects of the dialectic. For instance, I agree with Paoletti that [1] is ultimately the right way to go in resolving the above dilemma: that is, we ought to locate what is essential and necessitates the composition facts in the structure’s essence. However, I note that proponents of SPP must understand those essential facts about structures in a particular way. Specifically, for a given material X, X can simultaneously belong essentially to a kind of whole K (where X is a substance of kind K) and essentially belong to a kind of whole K* (where X is a part of Y, which is a substance of kind K*), the essential ordering among structures in hierarchical composition cannot be explained by structures themselves. Proponents of SPP must appeal outside of the relational essence of structures to something else that necessitates this ordering essentially. And, more particularly, I argue that the facts about how structures relate to composition facts comes apart on accounts that embrace SPP. Asian Journal of Philosophy (2026) 5:1 Page 7 of 24 1 Let’s start with the problem of structure- and kind-inheritance for views embracing SPP. SPP entails one material composite can have two or more structures, and therefore seemingly entails one thing belongs to two distinct substance kinds. But one thing cannot belong to two natural kinds of substance at the same time in the same respect (you can’t be both aardvark and an electron). Paoletti proposes two responses: it might be that structures are necessary but insufficient for kind membership, and then having a given structure as a part would not be sufficient for being an instance of a kind, or structures are sufficient for kind membership but themselves come in kinds, so that having one kind of structure constitutes an individual set of parts as a substance while having another kind of structure constitutes an individual set of parts a different substance. My version of the grounding problem begins here. If structures are insufficient for kind membership, then they do not necessarily relate their relata to that kind by their very nature, and so something else does (or nothing does), etc.; if structures come in different kinds, then belonging to a structurekind cannot be essential simply to being a structure, and so something else necessitates that a structure belongs to a structure-kind (or nothing does), etc. Since I reject ungrounded external relations, I think proponents of SPP need a story here. We all agree that the existence of S holding of composite A would necessitate that this composite A belongs essentially to kind K. Paoletti’s solution of adopting [1] would not resolve the above problem of explaining how structures relate to each other in composites, if SPP were true. We can show this by assuming that S’s existence necessitates that it does this essentially either for A qua particular or any composite substances of kind K. But the existence of S does not necessitate that composite A cannot belong to kind K*. This is because, if SPP is true, A could be a proper part of a substance B, belonging to kind K*. So, what necessitates whether A composes a proper part of that substance B of kind K*? It cannot be S, as the existence of S does not rule out A composing B as a part. Could it be S*, the structure which essentially necessitates that composite B, and that B belongs to kind K*? S* might seem to do the trick, since facts about what is essential to kind K* (to which B belongs) rule out parts of kind K (to which A belongs), and S* essentially composes or constitutes either B (the particular) or substances of kind K*. But there is nothing about S* qua particular relation that either necessarily rules out or necessitates having A qua particular as a relata (and so composing B as a proper part). We therefore need something else to necessitate that A qua particular composes B as a proper part (or cannot compose B), besides S, S*, A, and B. It was this grounding problem that I thought made SPP unworkable, because, like problem [2], the view cannot avoid an infinite regress. Now, Paoletti thinks I have overlooked possibilities here. Even if we accept that external relations cannot be wholly ungrounded, as I do, Paoletti thinks that we can accept that external relations either might be partly grounded in its relata, where the partial grounding is not supplementable: i.e., “the relation somehow depends on the relata and their features, but the latter are not enough in order to make it the case— and to necessitate—that the relation holds between them” (8), or that an external relation can be fully grounded and necessitated by a further relation (which is either not grounded in anything at all, or only partially grounded in the relata). I reject both options, since I have argued that composition facts ought to be necessitated by 1 Page 8 of 24 Asian Journal of Philosophy (2026) 5:1 the intrinsic properties of the material objects, in a mind-independent way. Since I think ungrounded external relations are not possible, I would rule out the second option of an external relation grounded in another external relation that is entirely ungrounded. That leaves grounding the external relation in something else which does necessitate that the relation holds or on an internal relation. However, I don’t see that these possibilities resolve the issue. We can therefore bump all the prior problems up to facts about what is essential to the kinds of composites or structures, as we would need to relate those facts about kinds to the particulars in question. We can then replicate the grounding problem in regard to the relation between what is essential to the kinds and to the particular structures and particular composites. As long as SPP is in place, structures, and structure-kinds, and substance-kinds cannot necessitate that one particular substance cannot compose another substance as a proper part. None of these facts can necessitate that a given particular part composes a substance; it would always involve external relations among them. This was my point in a later place, where Paoletti suggests that I hold a thesis that “being of a kind K fully grounds having a given structure S, so that, necessarily, anything of kind K has its material components structured by S” (Paoletti 10). I do not myself hold this view but was pointing out that, if structures hold necessarily of some given particular component parts and a composite only because of the natural kind to which the composite belongs, then natural kinds seemingly make structures explanatorily redundant (Paoletti 10). So, as long as proponents of SPP want something like structures to do explanatory work, the grounding of these external relations could not, in principle, bottom out in a relata or an internal relation that necessitates a given part composes another as a substance, since it cannot be essential to any particular part to compose any particular whole. That generates the regress. To illustrate, ingesting food brings items of different kinds to become part of me. My form explains why only material objects of a certain type can become part of my body. But, if SPP were true, it would never explain why those particular molecules that I ingest become parts of my body, because my form only explains or accounts for the generic constraints on what kinds of entities can be parts of me, not whether any particular entities actually compose me as parts. Nor does the form of xs explain why those xs become part of me, since the xs undergo no change in kind membership, and their kind does not essentially belong (solely by virtue of what they are) to wholes of kind y, nor necessarily does that particular form of each of the xs belong to a whole having the particular form of the ys. The pairing is mysterious. This is what I meant in saying that the problem is that there is no way for the proponent of SPP to explain “what makes it the case that the structure does constitute a particular material thing, since it is not essential to the structure that it constitute the particular material thing, nor is it essential to the material thing that any particular structure compose it” (Rooney, 2022: 45). Imagine the property of being a part of this particular whole. Imagine food molecules, when they become part of me, acquire these properties, which are sufficient for those particular food particles to come to compose me. But nothing about the molecules can necessitate that these properties hold, otherwise SPP would be false. The properties that the molecules exemplify would therefore need to be contingent Asian Journal of Philosophy (2026) 5:1 Page 9 of 24 1 or accidental properties by which those molecules are parts of me necessarily but undergo no change in kind membership or their individual identities. There is nothing about the parts that would ground an “internal relation” among that property and the particular parts in which that property inheres. If we appeal to some other property or feature of the parts that is contingent, we ought to find another property that is likewise contingent and unrelated to the identity of the parts, and so on. So, if food molecules are a part of me, and they are a part of me because of some other fact that contingently holds of me, but this fact likewise does not necessitate that those molecules are a part of me, we need another such property and so on. This is another version of the infinite regress. SPP fundamentally and generally gets the order of explanation the wrong way around: for SPP, it is necessarily only the essential nature of the wholes that ends up explaining why the parts compose the objects they do; the things which compose others as parts themselves need undergo no intrinsic change sufficient to change their kind membership. But belonging to a kind in this context is precisely to be a material composite. And that undermines the way that forms are supposed to account for restrictions on compositions, since all forms can be understood to generally explain a given x or y belonging to the kind “genuine material composite.” Positing external facts that necessitate the composition facts will end up in a similar place, because we still need to give some intrinsic properties according to which the composition facts follow necessarily from the situation of the parts, whenever they compose a given whole. I argue that SPP therefore generates a kind of incoherence, as the fact that a given y falls under the kind membership K is in virtue of whether the ys are essentially/necessarily composed of xs, whereas whether the xs fall under the kind membership K* is in virtue of whether the xs are essentially/necessarily composed of zs, and so on. And, so, by reductio, we ought to reject SPP if we hold fixed the explanatory project of offering an account of meaningfully restricted composition. Therefore, I agree with Skrzypek and Paoletti that we solve the problem by affirming that the parts and whole are essentially related. We can hold that the essential nature of the parts changes whenever some parts compose a (genuine) whole, then there is an essential or internal relation between those parts, the whole, and the property that relates them which does not hold contingently. Further, these properties can be essentially such as to be that in virtue of which some parts and some whole are the particular composite that they are, since there is no need for appealing to extrinsic factors that would “insulate” the parts from undergoing a change in kind membership when they become part of the composite. Instead, for hylomorphists, they are essentially related to a contingently existing third thing, the form/structure, which is “intrinsically and essentially correlative with the other parts of that object” (Skrzypek 7). We can characterize the property by which xs are to the ys in composition non-circularly, in terms of what is required for being a member of the whole, without needing to characterize the parts by facts about kind membership that are independent of the identity proper to the whole. What it is to be this particular x is thus only in virtue of what is essential to this particular y. This same relation would not hold independent of what is essential to these particular constituents of the composite whole. Consequently, we don’t need to characterize x and y as independently being particulars with identities independent of the composition they undergo and 1 Page 10 of 24 Asian Journal of Philosophy (2026) 5:1 thus don’t need to circularly characterize the composition relationship between them as dependent on their being the particulars they are, while simultaneously holding that the relation is entirely dependent upon their particular identities for its essential character. However, Paoletti ends up posing a serious objection that my view is incoherent because it admits both that there are hylomorphic forms that are grounded or necessitated fully by the parts, and that the material substances which exist are numerically identical with those composites. Paoletti notes that, “if structures were internal, they would be fully grounded by their relata. Therefore, they would be fully metaphysically explained and necessitated by their relata. When applied to material substances, this would entail the following: that the material components of material substances would be enough in order to fully metaphysically explain and determine that a given structure qua relation holds between them. Therefore, structures qua relations would play no crucial and irreducible explanatory role in accounting for the material composition of material substances. Their relata would be enough” (Paoletti 8). Further, Paoletti argues that composite material substances, like A, cannot be numerically identical with their structure S, or the parts B, C, and D, nor with the structure holding among B, C, and D [i.e., S(B, C, D)]. This is because “one and the same material substance has/can have distinct material components at distinct times” and consequently, “one and the same material substance has/can have distinct structures at distinct times” (Paoletti 12). That is, if structures were rigidly dependent on those parts’ existence, as in the case of a structure being (as Paoletti thinks) a relational mode, and structural complexes were numerically identical with the material substance, then we could only have momentary substances that were not robust in the face of change. Paoletti is right that if the internal relation held such that structures were “rigidly tied” to the material components they inform, such as B, C, and D, then structures on my account are like relational modes. In fact, that is precisely my resolution to this worry and what stops the dilemma generated by SPP—that structures or substantial forms are relevantly like relational modes of this kind. What Paoletti misses is my appeal to prime matter and the theoretical role that plays in the account. On the Thomistic view I adopt, structures rigidly depend upon composites for their essence and existence, but do not rigidly depend upon any particular parts for their existence and essence, although they depend upon kinds of parts for their essence and existence. Structures are thus internal relata whose holding is necessitated by the relata. But what it is to be a structure is not wholly grounded in the relata. To be a particular part, however, is wholly grounded in the structure and the composite. That is, I resolve the problem by putting composites and their parts existentially prior to structures, and I put structures essentially prior to parts. On my view, structures (i.e., substantial form) are less like “modes” and instead are more like manifestation of powers—i.e., an “actuality” of an underlying power or potency of material objects. A manifestation essentially relates to its power and the subject of that power but is not “nothing over and above” the power. Then, I hold that structures for material objects essentially and rigidly depend upon prime matter, a special Asian Journal of Philosophy (2026) 5:1 Page 11 of 24 1 kind of metaphysical part that constitutes every particular potential or actual part of a material composite.1 That is to say that structures are essentially manifestations of that power which is the prime matter of a given material composite. Integral material parts, then, all relate as consequences of what is essential to the manifestation of a given structure. Paoletti poses two problems against views like mine, on which a structure essentially relates to matter in a composite that is not individuated by the specific integral parts and is instead designated non-rigidly. First, there is a problem of “ontological extravagance.” Such views need to designate what it is that plays the relevant role alongside the structure and the parts that “makes up” the material composite. Clearly, I’ve said it’s prime matter, but Paoletti, Renz, and many others do not know what this refers to. “Is it a property such as the property of being an integral part which is such-and-such—that is had by distinct integral parts of A? Is it a role such as the role of being an integral part which is such-and-such—that is played by distinct integral parts of A? Is it a function that picks out specific integral parts at distinct times/in distinct possible circumstances? Is it a generic object? In all of these cases, we should accept that M is not what it seems to be, i.e., a plurality of material entities. It is something else: a property, a role, a function, a generic object… Subsequently, A is not what it seems to be, i.e., something that is also made of a plurality of material entities. It is something else: a bundle of properties (if F and M are both properties); a bundle made of a property (i.e., M) and something else (i.e., F, whatever it is); something that is made of F and of the possibly “open” collection (whatever this means) of all the realizers of role M/of all the results of applying function M to material entities; something that is made of F and of a generic object such as M; and so on. A is not a material substance anymore. It turns out to be something ontologically extravagant. Or at least something more ontologically extravagant than material substances” (Paoletti 15). I take prime matter not as an abstract object, generic object, function, but as a property of all material substances, and specifically a power. My brief statement about prime matter is that “prime matter is …not an integral part, but the potential to be a material object, considered apart from any particular actual way something could be a material object by being a member of a determinate kind of thing” (Rooney, 2022: 68). This does not strike me as ontologically extravagant, since it seems plausible that we can causally generate material composites and parts from other material composites and parts. There is therefore such power in material substances and their parts to generate new substances from their matter. What makes my view unique is that, from the Thomistic view, we can rigidly designate prime matter in terms of the causal history of a given set of substances. In short, that the prime matter of a given substance or its parts is whatever matter it came from, that is, whatever material substance generated it. The idea is as follows: structures depend upon their substances and the particular parts of those substances to come into existence, and, in virtue of composing some material parts as a proper part, those parts are the particular parts that they 1 Again, human souls depend upon this matter to come to exist but not to continue to exist. 1 Page 12 of 24 Asian Journal of Philosophy (2026) 5:1 are (which necessarily compose a particular material composite). But that structure is not essentially dependent upon any particular parts except having been causally produced from other material objects of the right sort: that is, the structure, the composite, and the particular parts that come to exist depend for their existence and essence upon the material substances from which these are causally derived. Structures thus require having come from those substances to have the right material parts upon which they rigidly and essentially depend, and this is what it is to say that they depend upon “prime matter,” but those structures do not depend essentially upon the particular parts that causally result. As substantial forms are precisely what allow us to identify a composite as numerically identical with the substance, since they are akin to relational modes holding between composites and prime matter, not between composites and the particular material parts of which they are composed. They therefore can explain the way in which composites are identical with those parts, while explaining that a composite does not cease to exist when those particular parts do. The Thomistic account thus helps respond to the worry that, if structures are internal relations among parts and composites, structures are explanatorily superfluous. Structures play a critical role in explaining how material substances come to be, change parts, and so forth. These can only play this role, however, if they are distinct from the composites and particular parts composing them. And, if those forms are to be internal relations among the composite and its parts, then there needs to be a corresponding matter that is not identical with the particular parts. The Thomistic framework of act-potentiality allows us to understand the way in which a structure being essentially an actuality allows it to play this role of being a relational mode: structures are essentially the actuality of prime matter, their corresponding potency or relata, rather than of any particular parts. Prime matter is a potency that inheres in all material objects but is only manifested diachronically over time. Consequently, substantial forms are the manifestations of that power of material substances to generate particular material parts/composites of another kind. The substantial form of the composite that generates the new substance is what constrains these powers, by reason of the proximate kind of matter it relates to essentially. Substantial forms thus play a role as being the particular nature of some matter, which is not the same as being the composite itself, since the composite is not just identical with its nature but the particular parts themselves. For these reasons, the nature of prime matter allows us to avoid a second problem Paoletti raises, which he refers to as the problem of “enriched material substances.” Paoletti proposes that, if we accept something like “prime matter,” then for any given composite A which is made up of its own substance and the extravagant matter M (my “prime matter”), then there is another composite, A +, where “A + is made of F, of the ‘extravagant’ M and of the very integral parts that ‘satisfy’ M at a given time/in a given possible circumstance” (Paoletti 15). However, on my account, when the integral parts that come to exist in a substance, whether at the beginning of the substance’s existence or at a later point in time when a substance acquires new parts from another substance, they will satisfy requirements relative to the causal powers of those substances from which they come, in relation to the substances Asian Journal of Philosophy (2026) 5:1 Page 13 of 24 1 which they come to compose. These diachronic requirements come from the structures of each of those substances. On this view, composites and their parts rigidly depend on the matter of other things to be generated (NB: material part or substance depends on another particular substances to be generated as that particular material substance or part that it is, but not necessarily on that particular substance to be the kind it is.). This explains the sense in which Thomists maintain that prime matter has no nature in itself apart from a composite—it is not any kind of matter, but only a power to generate material substances. Prime matter would not be designated by referring to the spatial dimensions of those substances it “composes” as a metaphysical part, or by specific spatiotemporal coordinates (pace Paoletti 16). Rather, prime matter is a power of which the integral parts are manifestations. Integral parts are indeed constantly manifesting or actualizing the powers of the prime matter from which they come. But prime matter has no essence or existence apart from these particular integral parts or substances. This character as being a property is what ensures that prime matter could not be a further integral part alongside the rest, and instead can exist only as an attribute of the composite/parts that exist. Further, prime matter is precisely a power which (on my account) ultimately can be borne primarily or essentially only by property bearers, substances, and not their integral parts. To designate this power, then, we would refer to the substance. And, as there wouldn’t be the possibility of a distinct M which could be designated apart from the substance itself and what is essential to it or to its parts, Paoletti’s problem does not get going. 3 Jeremy Skrzypek Jeremy Skrzypek wonders “why can’t we say that those other parts themselves possess correlative features or relations which allow them to come together to compose some further whole? … if what is really solving the problem is the intrinsic correlativity of the parts and the further object, element, or principle by which they are unified, why can’t we transfer that intrinsic correlatively to the parts themselves?” (Skrzypek 6). I don’t think structural hylomorphists can agree to this, as SPP holds that parts are the same whether they compose an object or not. It could be essential to the parts that they compose what they do, when in appropriate external relations to each other, but I take it that in such circumstances the parts cannot essentially compose a whole to be what they are; they would just be essentially disposed to compose another. Consequently, if it were essential to the parts that they (actually) compose what they do (at every time), then it looks like those parts cannot cease to compose that whole while remaining the parts they do. This contradicts the SPP thesis, and that was the context in which I made these arguments. Skrzypek suggests that the response of the proponent of SPP should be “that natural kinds and forms and essences are prior to one another in different ways. He or she could say that natural kinds are epistemically prior, whereas forms and essences are metaphysically prior” (Skrzypek 9). I concede this is true, but it does not work to resolve the problem, since (as I will show) the problem lies not in whether kind membership is prior epistemically or metaphysically to essences or structures, but 1 Page 14 of 24 Asian Journal of Philosophy (2026) 5:1 what the essential relations could be among parts, wholes, and kinds, given SPP’s constraints. Specifically, it cannot be universal truths about kinds of wholes that explain what parts are essential to them. But appealing to individual essences for each whole would not do the trick either. Even if wholes are essentially related to their parts, parts are not appropriately essentially related to their wholes if SPP is true. So, what I am arguing is that proponents of SPP cannot in principle resolve the pairing problem among parts and wholes by appealing to the way parts and wholes stand in essential relations (as Skrzypek concedes we should). Skrzypek misunderstands my criticism of Koslicki as a worry that, since she holds that structures are literally parts of each object and thus that there is only one parthood relation across all objects, it should be the case that each object essentially belongs to multiple (incompatible) kinds simultaneously (Skrzypek 8-10). However, my point was that, in stopping this transitivity from occurring, Koslicki must appeal to facts about what is essential to each structure, at each level. In complex wholes, commitment to SPP requires that each structure is not essential to the parts of the whole, and only essential to the wholes at each given mereological level of composition. So, Jeremy suggests that structural hylomorphists who are not Koslicki could hold that there are different species of parthood relation, breaking transitivity, or that “a thing has to not only possess a kind-making structure among its proper parts, that kind-making structure must also figure into the essence of the thing” (Skrzypek 8). (The latter is my own suggestion for Koslicki’s view on Rooney, 2022: p. 59.) But, as I note, it then follows that we don’t need the form—just the essences of the wholes and the parts to be appropriately related (Rooney, 2022: 60)—or, the form would only be that in virtue of which the parts are disposed to form wholes, rather than that in virtue of which composition facts are necessitated. Further, it would need to be essential to this structure qua particular that it belongs to the whole qua particular, as it would be for the parts. Yet “kind membership … determines whether something is a whole [so] structures are merely necessary, but insufficient conditions for whether some parts belong to a kind” (Rooney, 2022: 59), because “natural kind membership, and the essences appropriate to those kinds, are universal” (Rooney, 2022: 60). That is, the essences correlative with kinds are not particular in the right way; what is essential to being human or a cat could not necessitate composition facts about particular humans or cats. I argued that trying to particularize kinds and essences will not do the trick, since it just shifts the problem elsewhere: even if an atom’s numerically distinct essence necessitates the composition facts regarding its parts, it cannot necessitate the composition facts regarding the wholes of which it is a part, without violating SPP. So, while the proponent of structural hylomorphism could hold that the structures of wholes are essential to those wholes, SPP requires denying that structures of wholes are correspondingly essential to the parts of those wholes. This is what makes the pairing problem insoluble; it just ends up deferred somewhere else. Skrzypek alleges that I too quickly in dismissing material artifacts as genuine material objects, because artifacts “are not substances [but] they are composed of substances [and] are, nonetheless, genuine material objects” (Skrzypek 11). However, I laid down in the book a stipulative definition of “substance” where substances just are the same as “genuine material objects” relative to criteria for Asian Journal of Philosophy (2026) 5:1 Page 15 of 24 1 restricted composition. If Jeremy wanted to count artifacts as genuine material objects, then they would count as “substances,” by that stipulative definition. Given this definition, however, when there are some parts composing a composite genuine material whole, if an x composes that whole as a part, that x cannot also be a whole, since there is no relevant other sense of “whole” (without SPP) except the highest level of the compositional hierarchy. Consequently, if we reject SPP, then it is not possible for there to be a genuine material whole to be composed of another whole. Near the end of the book, I propose some considerations that, given the motivation for restricted composition and hylomorphism, hylomorphists ought to hold that the class of the genuine material objects is derived from kind membership in natural kinds—all and only the members of natural kinds are genuine material objects. And, for my money, I wouldn’t think artifacts fall under a natural kind, and so I would want to deny that they are substances. (Jeremy seems to agree). But I can grant many of Jeremy’s claims about artifacts—that “they exist, they possess their own parts, they exhibit certain structural relations between those parts, they possess certain properties and powers, perhaps even some that are emergent, and, perhaps most importantly, they are everywhere” (Skrzypek 11)—without conceding that they are members of natural kinds. I would instead suggest that the hylomorphist can consider there to be different species of parthood relation. On my view, SPP is a thesis about substances composing other substances as parts. Those who reject SPP can nevertheless concede that there are distinct kinds of parthood, and not every kind of parthood is substantial parthood composing a genuine material object, an instance of a natural kind. While I mentioned that scholastics believed in accidental forms (e.g., Rooney, 2022:77), I tried to refrain from confusing the discussion by invoking two distinct species of parthood, one for substantial and another for accidental forms. But it is by appeal to such properties that I would respond to Jeremy’s problem: artifacts are those things composed of genuine material objects which share an overlapping part—an accidental form—and thereby constitute an artifactual object. These are not members of natural kinds, and they do not bear properties/ powers in their own right but only in virtue of their parts, but they form a kind of a whole, but in a different sense from that meant by genuine material objects or substances. And I agree with Jeremy that “it could be that structural hylomorphism just is a theory of composite material objects as artifacts” (Skrzypek 12). Yet the problem remains that, if we admit a principle into our ontology that makes all substances artifacts, this will imply (on my stipulative definitions) that there are no genuine composite material objects. That would be mereological nihilism, not a variety of restricted composition. In the book, I refrained from getting into the issues of deciding whether there were any natural kinds of material object, and that would be—I suggest—the way to decide whether nihilism or restricted composition is the true view of the world. But my arguments against theories of restricted composition involving SPP would still stand, regardless of whether there were any genuine composite objects, since the arguments only 1 Page 16 of 24 Asian Journal of Philosophy (2026) 5:1 aimed to show that accounts of restricted composition involving SPP are incoherent theories. That can be true even if there are no composites. 4 Fabio Ceravolo Fabio Ceravolo critiques my responses to various objections to the Thomistic alternative that I sketch, where things undergo changes of kind membership in virtue of either composing or decomposing substances. My explanation, in short, is that nothing about becoming or ceasing to be a substance requires that a part which was formerly a substance to be totally unrelated to what it was formerly. That is, there can be integral parts that possess very similar properties with the substances that they were before composing the whole. And, given that there is a special continuity in causality, where the substance causes the part, and the part was that substance (i.e., given continuity of prime matter, the part is a result of that substance manifesting powers essential to the kind of thing it is), we can explain that the new part was not a token replacement look-alike that comes into being “ex nihilo.” Rather, there is a necessary continuity between the kind membership of the substance and part it forms in composites, just as there are necessary similarities between their essential properties. Ceravolo worries, as follows, that my response to these objections involves a problematic “lack of generality” (Ceravolo 6). He proposes that my analysis cannot explain the continuity of properties in cases of heart transplants, where “the average output of a mature adult heart exceeds that of a human embryo and forcing embryonic hearts to generate adult-equivalent outputs causes irreparable structural damage. Thus embryonic hearts lack and cannot acquire the power to maintain adult-equivalent flow. But explants don’t alter cardiac output: excised hearts can sustain blood flow at identical rates (when connected to a machine or re-implanted). Thus this retained power needs explanation.... Rooney’s explanation, adapted to this case, is that the power to sustain adult-equivalent output is something ‘a heart’‘essentially included’ in the donor body’s proximate matter shares with the body’s integral parts. But not every heart in the body’s proximate matter can share that power. An embryonic heart, as we have just seen, couldn’t. So if the ‘heart essentially included’ in the body’s proximate matter were an embryo’s heart, the power to sustain adult-equivalent output could not have its persistence after surgery explained as Rooney demands” (Ceravolo 6). However, I never claimed that the proximate matter of a given material composite involved only generic kind-facts like “having a heart.” I noted that the heart itself (the part of me) is an integral material part with its own (accidental) form. Consequently, my heart can have its own particular properties and capacities, not merely those generically true of the kind “heart.” This was indeed central to my analysis of radioisotope tagging, where molecules can be so tagged and form part of my chemical structure while continuing to exemplify the property of being tagged. What I said was that such molecules are no counterexample, since they do not need to take on generic properties of a molecule-part when they become part of my chemical structure; there can be a continuity of properties in Asian Journal of Philosophy (2026) 5:1 Page 17 of 24 1 virtue of the particular molecule-substance being of such a character as to essentially cause a certain particular molecule-part when it forms part of me. So, the fact that my heart is capable of pumping blood within my body at a certain rate, and is capable of doing so outside my body, is unmysterious from my point of view. The heart as an explant and the heart composing my body are appropriately and essentially related. The same is true of embryonic hearts. I don’t see anything I’ve said that would force me to say embryonic hearts, when disjoint explants, are capable of pumping just as much blood as adult hearts. Ceravolo proposes an objection that “it doesn’t seem material natures can necessitate every composition fact” (Ceravolo 8). He proposes this counterexample: “Consider a fact that specifies an object’s current and actual make-up, such as the fact mentioned above that the 52 cards on my desk compose my poker deck. Material natures that necessitate actual make-ups could not belong to objects with different arrays of parts. For instance, a deck made of 51 of the 52 cards, existing at a world where the 52nd card doesn’t, couldn’t have the same material nature... [And] if the 51- and 52-card deck were the same deck, there wouldn’t be two natures but only one, since no material object has more than one nature, and as just seen, that unique nature could not necessitate that the deck is made of the 52 cards.” (Ceravolo 8). Ceravolo is appeal to considerations in regard to what I have termed the “pairing problem” for SPP. To avoid the problem I alleged affects SPP, where parts are not essential to their wholes or to the forms/structures that compose those wholes, I seem to be saying that substantial forms are essentially related to particular wholes and to the particular parts that compose them. But then, if that were true, every composite material object would cease to exist when even one part ceases to or comes to compose the whole, and those forms should likewise cease to exist when the particular parts cease to exist. That is, all parts would be essential to every material whole. Ceravolo, however, has failed to note that my position is not that the parts are essential to the substantial form. My view is that each of the parts individually essentially depends upon the substantial form for what that part is qua particular and depends essentially upon the whole for facts about what it is generically (the kind of part it is). But the substantial form and the whole do not necessarily depend essentially on any particular parts for what they are. So, when I drink some espresso, the caffeine molecules from the espresso are metabolized by my liver via one of its enzyme systems, and there is a complex series of reactions that demethylate the molecule and break it down into other molecules that interact with proteins elsewhere in my body. My liver enzyme system is essentially set up to react in this way with molecules that are similar in structure to caffeine, and my other proteins are likewise essentially set up to react with the products of this reaction. When the caffeine products (paraxanthine, theobromine, and theophylline) interact elsewhere and eventually they or their parts end up in other chemical compounds, they end up forming part of me. Those products are parts of me then, in virtue of undergoing a chemical change and entering into bonds with parts of me, such that the parts essentially depend upon the larger compound they form for what they are as a kind of part and depend upon the substantial form of me (via the accidental form of that integral part) as the particular part of me that they are. 1 Page 18 of 24 Asian Journal of Philosophy (2026) 5:1 The reason for introducing substantial forms, then, is to ensure that we can differentiate what is essential to kinds of wholes from what is necessarily the case when particular parts compose particular wholes. The latter, the composition facts, ought to be necessitated by the intrinsic properties of that whole, without those particular parts being essential to either that whole or to wholes of its kind in general. Substantial forms are just the thing filling this functional role. To respond to Ceravolo’s proposed counterexample, then, I would say first that decks of cards are artifacts, having no nature above and beyond the natures of each individual part. There is nothing essential to being a particular card which essentially depends upon composing a particular deck; that card would be the same particular card it is if it composed a distinct deck or did not. This follows more generally from the fact that cards are not essentially dependent upon decks in general for their character as that kind of thing they are. Artifacts like cards are not intrinsically different in virtue of our (e.g.) imputing or assigning them purposes. I don’t have to count the card as a card for it to continue to be what it is, with all its same intrinsic properties. As I already mentioned in connection with Skrzypek’s objection, I wouldn’t think that we need a substantial form to account for the unity of decks and cards, since they are (by my lights) pseudoobjects and not genuine material objects. Recall my combination argument here: if there were worlds where cards and decks composed each other and where they did not, and no intrinsic properties were distinct in the worlds where cards composed decks and where they did not, I would suspect that the truths about composition varied only in virtue of the mind-dependent attitudes of people who considered cards to compose decks of cards. And then I would not think that decks of cards count as genuine material objects. My theory, however, was only intended to posit material natures or substantial forms for genuine material objects. It is not therefore a counterexample that my theory has no place for substantial forms of pseudo-objects. Ceravolo is worried that I have thereby neglected describing what forms do beyond the mereological work of accounting for composition facts, since substantial forms are described functionally in terms of their fulfilling a role in accounting for material composition. But, from my perspective, my arguments and their overall goal was to prove that all accounts of restricted composition which are coherent are hylomorphic. There are substantive disputes between hylomorphists regarding how to conceive genuine material objects, natural kinds, and how substantial forms function. I cannot take sides on those matters while trying to prove conclusions related to hylomorphism in general, as a class of possible views. So, I took a general view of what is essential to being a hylomorphist: positing substantial forms that explain material composition facts. Even if being a “true hylomorphist” requires something stronger, I do not see any reason to think that this nominal quibble would render my conclusion any less substantive: that every coherent theory of restricted material composition posits functional equivalents to substantial forms. Moreover, Ceravolo poses a worry that if I have not described the way in which substantial forms are “parts” of their composites, then I could potentially get myself in trouble. Since a substantial form z is a wholly overlapping sort of part, every integral part x1, x2… xn of a given composite whole y will have that substantial form as a part of it. Because z is a part of every part of every x, then z is a part of every Asian Journal of Philosophy (2026) 5:1 Page 19 of 24 1 part of every part of every x and so on. But Ceravolo nevertheless thinks that this implies that substantial forms “have parts of their objects as parts” (13), because he is thinking of parthood as a symmetric relation. Thus, if a substantial form z overlaps with all of the xs and the y, then the substantial form has all these things as parts of the substantial form. And it looks, further, as if the substantial form is part of itself (see Ceravolo 13, fn. 17). I take it, then, that Ceravolo’s worry is both that a substantial form cannot have material objects as parts, since it does not belong to the same ontological category, and—more seriously—that if substantial forms have themselves and other things as parts of those forms we would need a unifier. That is, we would need another substantial form to account for the composition facts about substantial forms. And that generates an infinite regress. In the book, I respond to the first of these worries. I note that “forms are parts of substances in a way that involves a distinct parthood relation from material parthood. Forms have a distinct kind of parthood relation to the material composites than those integral parts, but they are distinct from their composites and their relation to those composites is a reflexive, asymmetric, transitive relation” (Rooney, 2022: 93). So, I am distinguishing that “overlap” is only intended to be an asymmetric relation by which the substantial form is a part of every other integral part, but that the whole and parts are not parts of that form. Since these things are not parts of the form, no further unifier is required, and the regress stops before it starts. The relation is reflexive, however, and Ceravolo might think that the substantial form z would require a further unifier to compose itself as a part. I am not convinced that this would generate a regress, as I would hold that this is an essential feature of every object, because of the generic parthood relation. But I am also not sure why I cannot say that substantial forms compose themselves as metaphysical parts in virtue of…themselves! My implicit stipulation regarding that in virtue of which composition facts hold was clearly always facts about material composition, not metaphysical composition, so I don’t see that this move contradicts my other theoretical claims. But, if this were thought a problem, I can hold that the substantial form is just that part which essentially unifies every material part in each composite, whereas the substantial form is a metaphysical part of that composite, and it is the composite that essentially accounts for the substantial form being a part of that composite (and that particular substantial form) as well as for the substantial form being a part of itself. And this is not unprincipled, since it is essential to composites that they have forms of given types. So, if a given composite exists, the existence of the composite is sufficient for the existence of a corresponding substantial form, and the substantial form (ordinarily2) essentially depends on that composite for its own existence and particular character. And so there is no infinite regress. 2 Except for human souls. 1 Page 20 of 24 Asian Journal of Philosophy (2026) 5:1 5 Graham Renz Renz alleges that I have moved too quickly in concluding that, if restricted composition is a mind-independent matter, we must conclude that forms (or whatever it is in virtue of which some parts compose a whole) are intrinsic to the parts that compose wholes, or that forms must have distinct identities from the wholes or parts they compose. He proposes an alternative account of composition invoking powers and their manifestations. Why do two things—like electrons and protons—compose one new material object, a hydrogen atom? In virtue of “the manifestation of the powers of the proton and the electron,” such that “when objects with these powers are properly mingled, those powers manifest such that their possessors unite” (Renz 9). Renz takes this as a counterexample to my case that whatever it is in virtue of which two or more xs compose a y needs to involve appeal to a further z which is not identical to the xs or the y. What Renz seems to be saying is that, when these two particles come closely into appropriate distance, they engage in a joint manifestation of their powers. But to jointly manifest a power, or to interact in producing a joint manifestation, is not to become one subject in which that power inheres. If there is not one power at the end but two, I don’t see that material composition has occurred, since there is no new subject produced. And Renz says this explicitly later, saying that the proton and electron still exist as continuing to exercise their powers. So, a world in which there are still two material objects (the particles) after the manifestation, rather than a composite material subject, does not look like a counterexample to my claim. It just looks like two things independently manifesting powers that interact and thereby being in an accidental relation. Renz likewise argues we can give a scenario on which we do away with a need for forms to be intrinsic to what they inform. Renz says that “powers are possessed by the parts. But… the manifestation of powers [is] a happening, not a property, feature, or relation born by a subject. For, it seems wrong to suppose that either the proton or electron possesses or bears the manifestation of both their powers, and it also seems wrong to suppose that the hydrogen possesses or bears it either: for the hydrogen just is the proton and electron manifesting their powers” (Renz 10). Renz also says that “there’s no metaphysical difference between the manifestation of the powers of charge possessed of the proton and electron and the manifestation of the powers possessed of, say, two electrons” (Renz 11). Renz thinks the fact that it is mind-independent that there are electrons, and protons, and objectively are engaged in manifesting their powers, would all be sufficient to avoid the implication that the fact that these objects form one whole is mind-dependent (Renz 10). If a simple is not intrinsically distinct when it manifests a power and when it does not, and no new manifestation is “triggered” by interaction with another power, but what occurs is only the spatiotemporal congruity of two distinct manifestations overlapping or appearing to us in a different way, then I do not see that any new property has emerged. The same properties continue to be in play, with just different appearances given the way that they are apprehended. By contrast, it seems to me that if a simple is intrinsically distinct in the state where it manifests a power and where it Asian Journal of Philosophy (2026) 5:1 Page 21 of 24 1 does not, then we can speak of properties of those simples. And it seems to me that there is a metaphysical difference between similar powers, like charge, manifested by distinct subjects: the fact that it is a distinct subject manifesting a numerically distinct power, in each case, even if the powers and their manifestations are exactly similar in other respects. As with the previous counterexample, while Renz thinks we have explained the way in which these particles ought to be counted as one material object, I simply do not see that the counterexample involves the subjects (the particles) actually being one object in the sense relevant for material composition. They do not seem to compose one another, and there is no one subject of the powers. And, if Renz thinks that manifestations are “happenings” rather than anything intrinsic to the particles, the true subjects of powers or their manifestations, then I do not see that “happenings” are anything more than co-located events of some sort. To be one happening is not to be one material composite object or subject of properties. Renz’s counterexample then seems like a world where there are no composite material objects, and instead just simples and artificially grouped-together “happenings.” Graham elsewhere counsels that hylomorphists ought to accept a view on which, for a material composite A composed of B and C, they can affirm that “while A is a whole, it does not belong to a category as fundamental as B and C. This is to countenance the reality of wholes but does so in a way that weakens the unity and so fundamentality usually ascribed to substances by hylomorphists” (Renz 8) because, in the end, “there are no metaphysically salient borders between what we would ordinarily take to be genuine objects and pseudo-objects or mere sums” (Renz 11). That looks indistinguishable from thinking that composite material objects do not really exist, since they only seem to exist in virtue of us treating temporally or spatially co-located events as having or being one subject or object. That doesn’t look like a counterexample; it seems to be nothing more than a perspective on which we consider certain effects to have one subject, perhaps for practical purposes, but where mereological nihilism is the deep truth and such effects occurring involve no “coming-to-be” of any new subjects that were not there to begin with. So, in response to Renz’ question, “why not suppose that when primitively simple substances are structured, configured, or otherwise caught up in some appropriate way that those substances form a new substance and so cease to exist as substances in their own right, as in, e.g., Marmodoro 2013?” (Renz, 8, fn. 8), I would say that whatever it is in virtue of those things getting “structured” and forming a new substance, it ought to be an intrinsic property of those parts that form a given whole, and it ought to be such that there is a distinction between that property, those parts, and that whole. If there were only accidental relations among intrinsically distinct material simples, then I don’t see this as a world in which composition occurs. Since the counterexamples fail, I conclude that for any world in which (restricted) composition occurs, by contrast, it ought to be that parts compose wholes contingently, not merely necessarily whenever the parts exist, and that, when parts do compose a given whole, they compose that whole in virtue of something like a property which is essential to the parts and the whole. And I think it would not make much sense to think of hylomorphic compounds in a world of mereological nihilism, as Renz envisions the world, since I would think that the really existent substances and property-bearers in this world are the 1 Page 22 of 24 Asian Journal of Philosophy (2026) 5:1 partless simples. Whatever and however complex an artifactual form was, it would bottom out “immediately” in properties of simples—because properties cannot bear properties—and there ought to be no relevant “levels” of mereological composition, if there are no ontologically distinct “levels” of properties (I grant there might be taxonomic, descriptive, logical distinctions by which we could distinguish levels of properties, but these distinctions would not be ontologically perspicuous (Heil, 2012: 165). This would, I think, render hylomorphism very uninteresting, because the perspicuous story would be the set of properties of those simples. And, if Renz thinks there are no properties, only happenings of simples, then the world seems simply particles “flatly” distributed over time and space. There doesn’t seem much of any place for hierarchical composition explainable by functional roles of matter or form. This leads into the last species of criticisms of my view, which are roughly that my positive proposals are mysterious or ontologically extravagant. Renz argues that: “[Rooney’s Thomistic hylomorphism] appears to require us to countenance the heavy-duty machinery of metaphysical parts or constituents whose natures are seemingly ineffable. To meaningfully restrict composition without falling into incoherence, Rooney suggests we endorse a theory positing prime matter, an indeterminate potency to be a material thing of some kind or other, and construe forms as actualities. But prime matter and actualities detached from subjects are nothing we ordinarily bump into in everyday experience or hear mention of in scientific discourse. Nor are they, I’ll confess, easy to get a firm mental grip on… even if we take it that forms are primitively and essentially actualities (Rooney 2022: 72), we can still reasonably ask about the natures of forms themselves. They must be distinct from the substances of which they are parts (Rooney 2022: 72, 92, 161), and so, they are not actual material substances. But, again and even still, what are they? No clear answer is forthcoming” (Renz 8). I would respond that “powers” and “manifestations” are no more scientific terms than “act” or “actuality,” nor do we ordinarily employ these terms in a technical metaphysical sense in our discourse, nor is it easy to define what these are, nor does it seem as if we can give a perspicuous scientific or empirical answer as to the natures of powers or manifestations in themselves. But I think there is a problem with this set of questions, especially the last. I don’t know what it means to describe the nature of powers or manifestations themselves. I think we only use such terms as a kind of functional set of distinctions. There are no power or manifestations “themselves” apart from particular powers or dispositions or manifestations, which are functionally described in each particular context where they occur. Manifesting a power to smoke a cigarette is quite different from manifesting a power to be visible or cognizable is quite different from manifesting a power to repel or attract by negative charge. But I think these facts do not mean “power” and “manifestation” are ineffable concepts, or that powers and their manifestations are ineffable. I think I have a good mental grip on what power is. What Renz misses, more importantly, is that “potency” and “actuality” are terms closely related to, and often synonymous with, “power” and “manifestation” (see Rooney 74–75). “Manifestations” are “actualities,” and “powers” are “potencies.” The only difference is that my terms are broader categories for two Asian Journal of Philosophy (2026) 5:1 Page 23 of 24 1 kinds of powers/manifestations, which are (roughly) the power/manifestation appropriate to a subject and the power/manifestation appropriate to properties that inhere in subjects. Since “power” and “potency” (for instance) are essentially synonymous, I think there is no serious difficulty in understanding what my terms mean, and getting a solid mental grip on them, if we can get a grip on Renz’ terms. (I concede that “prime matter” requires more technical introduction, but it too does not seem impossible to build up from these basic concepts and requires nothing much beyond them. Yet, in fact, there might be scientific technical concepts in the neighborhood to “prime matter,” so that concepts related to it are regularly encountered in physics (Oderberg, 2023)). I would not agree with Ceravolo’ that these distinctions between whatever plays the function role of powers and their manifestations, or act and potency, is what justifies existence claims about composite objects (see Ceravolo 8). Instead, I take it these terms aim to functionally pick out aspects of phenomena existing in the world: i.e., facts about powers and manifestations are mind-independently true, as are the facts about whether there are material composites. In any event, if functional characterization of these terms leaves us unable to answer what these things are in “themselves,” and thereby are supposed to leave us referring to ineffable entities, and this is bad for our theory, then Renz’ own theory will suffer exactly parallel (if not identical) worries. I also do not see that my distinctions between power and manifestation commit us to any more heavy-duty metaphysical machinery than Renz’ commitment to power and manifestation, since I take myself to be drawing the same or very closely related distinction. What I seem to be committed to, beyond Renz, is the existence of composite material objects and their properties. But I don’t think this is an unreasonable commitment. Hylomorphism is just what we need to make good sense of the data. Funding Open access funding provided by Hong Kong Baptist University Library. Data availability I do not analyze or generate any datasets, because my work proceeds within a theoretical approach. Declarations Competing interests The author declares no competing interests. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/ licenses/by/4.0/. 1 Page 24 of 24 Asian Journal of Philosophy (2026) 5:1 References Heil, J. (2012). The universe as we find it. Oxford University Press. Masterman, C. (2025). Can we repudiate ontology altogether? Noûs, 1–29. https://doi.org/10.1111/nous. 70006 Oderberg, D. (2022). Is prime matter energy? Australasian Journal of Philosophy, 101(3), 534– 550. https://doi.org/10.1080/00048402.2021.2010222 Rooney, J. (2022). Material objects in confucian and Aristotelian metaphysics: The inevitability of hylomorphism. Bloomsburg Academic. Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.