© 2010, American Catholic Philosophical Quarterly, Vol. 84, No. 1

On Substance

Patrick Toner

Abstract. In this paper, I offer a theory of substance. There are three steps in the argument. First, I present and explain my definition of substance. Second, I argue that the definition yields the right results: that is, my definition rules that (among other things) events and universals, privations and piles of trash, are not substances, but at least some ordinary physical objects are. Third, I defend the definition by rebutting two obvious objections to it.

I would begin with the obligatory Aristotle quotation about how the question of “what being is” is “what is substance,” but you’re already more than familiar with that. So I’ll just dive in and say that the point

of this paper is to provide a theory of substance. First, I present and explain my definition of substance. Second, I argue that the definition yields the right results: that is, my definition rules that that events and properties, inter alia, are not substances, but ordinary physical objects such as organisms (and, if there are such things, angels or disembodied souls) are substances. Third and fourth, I defend the definition by rebutting objections. The paper closes with a brief appendix where I alter my definition slightly in order to bring in the notion of a substantial kind.

It is a fine thing to have a defensible theory of substance that seems to get the right results, and that seems able to stand up to obvious objections. But this theory has a particular attraction—namely, it solves a number of perplexing ontological puzzles, such as the “Problem of the Many” (section IV). So this is a useful theory. That should count as a significant point in its favor.

I.

The Definition of “Substance.” My definition of substance is a partisan one, in two ways. First, I do not try to make it fit with every notion of substance that has ever been deployed by any prominent philosopher. I’m not trying to explicate how the word “substance” is typically used in philosophical discourse (if there is a typical use). I do think the definition captures much of the ordinary notion of

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substance (to the extent that there is an ordinary notion), but it doesn’t capture every such sense. Second, although a definition of substance shouldn’t simply sweep aside deep ontological questions (by, for example, being formulated in such a way as to rule out God’s existence—or rule it in), it does seem quite rea-sonable to define substance within the context of certain other commitments. Some of my other commitments—commitments within the context of which I offer my account of substance—will come out in the course of this paper. Some are controversial. Upon discovering these commitments, the reader will simply have to decide whether to stop reading (since any account of substance that makes such suppositions must clearly be false and pointless), or to keep reading to find out if there may be any value in the view. At any rate, I don’t strive for neutrality here, though I take for granted that common sense should be preserved if possible, or, at least, very carefully explained away if it must go.

With that said, here is the definition of substance:

X is a substance = df. X is a (i) causally efficacious (ii) non-exemplifiable (iii) particular which (iv) can persist, which (v) is not a non-separable part of anything, and which (vi) has no separable parts.

Before I defend the definition, I must explain it. So, for the remainder of this section, I will simply make clear what I’m claiming. The arguments intended to show that this is a good definition don’t start until section II.

Item (i), the causal efficacy condition, is a tricky one. I won’t be able to fully explain it here, because I won’t give a theory of causation, and I’d really need to do that in order to give a complete account of this condition. But I’ll say a couple of things that may help.

Many philosophers hold that the causal relata are events: but if events are the (only) causal relata, then given condition (i), all non-events turn out to be non-substances. But that’s not a very attractive view at all. The obvious response is to deny that events are the only causal relata. And that I do. In endorsing (i), I commit myself to the position that event causation is not the whole story. This is a commitment I gladly embrace. When a dog buries a bone, one thinks that the dog is causally efficacious, and not just the event of the dog’s digging. Surely, Alexander’s Dictum is on my side here: “to be is to have causal powers” is an intuitively plausible claim.1 Exactly how to spell out what it is to have causal powers, or how causal powers come to be involved in causal interactions, is a difficult thing. But to take for granted that objects can be, in an important sense, causes, is hardly revolutionary. I can understand why some would be unsatisfied

1The name “Alexander’s Dictum” was coined by Jaegwon Kim, “The Nonreductivist’s Troubles with Mentaoin Causation,” in Mental Causation, ed. J. Heil and A. Mele (Oxford: Oxford University Press, 1993).

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with this very quick gesture in the direction of a very serious philosophical issue. But I can do only so many things in one paper, and giving a satisfactory account of causation is not one of the things I can do here.

Conditions (ii) and (iii) are fairly straightforward and need, I think, no explanation at this point.

There are two things to notice about condition (iv). First, it claims that substances can persist, not that they can perdure or endure. (Presumably, they persist by doing one or the other: I just haven’t specified which.) As we’ll see later on, perdurance is going to be ruled out by (vi). But I don’t want to make endurance a part of the definition itself, since to understand endurance, we need to understand being wholly present, and many philosophers claim to find the notion of being wholly present quite difficult to grasp. Since my defini-tion is going to push us to accept endurance anyway, why not just use it here? Because being pushed to accept endurance (even if you don’t fully understand it) because you find this definition of substance to be true, is quite different from having to take endurance for granted in order to get the definition off the ground.

Second, the condition is that substances can persist, not that they do persist. In the normal course of things, I take it that substances (all) persist. But there’s nothing incoherent about God creating a substance like you or me, allowing it to exist instantaneously, and then annihilating it. In such a case, it would be the sort of thing that could persist, despite having failed to do so.

That leaves (v) and (vi): the parthood conditions. The claims are that sub-stances are not non-separable parts of anything, and themselves have no separable parts. To understand these claims, we need to understand separability and non-separability. It would be easy to misunderstand those terms. So: to claim of a part that it is non-separable is not to claim that the thing of which it is a part can’t survive without it. That is, it’s not to claim that the part is essential to the whole. On the contrary, it is to claim that being part of that whole is essential to the part. Here is (what I hope will be) an obvious example of this: the left-hand third of my desk is essentially part of my desk. If it were to be removed from the desk, so that it was no longer a part of my desk, it wouldn’t be the left-hand third of my desk anymore. It would still be the same parcel of wood, yes. But it wouldn’t be the left-hand third of my desk.2 To be that, it actually has to be part of my desk. (Whether the desk can survive the removal of that part is an entirely distinct question on which I need take no position here.)

Another way to put this is to say that a non-separable part is internally related to the whole. Here’s what I mean by that. Consider the property F, which is

2The example is from E. J. Lowe, Subjects of Experience (Cambridge: Cambridge University Press, 1996), 36.

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the property of standing in the internal relation being a part of X. (F is not the relation: it is, rather, a necessary correlate of the relation.) G. E. Moore gave a fine account of what is involved in saying something exemplifies F: “supposing A has F, then anything which had not had F would necessarily have been dif-ferent from A.”3 On this account of non-separable parts, the claim being made is very simple: X is a non-separable part of Y if X could not possibly exist and not be a part of Y. That seems to be the case with the left-hand third of my desk. Again, that parcel of wood could exist without being part of my desk. But the left-hand third of my desk could not. At least, that’s what I think—and I must say, it seems awfully plausible. (If it strikes you otherwise, please hold on: I’ll say much more about this in what follows.)

A separable part, on the other hand, is not internally related to the whole of which it is a part. Take the screw that holds the leg on my desk. It is, let’s suppose, a part of my desk. If I remove it, it remains a screw—the same screw it was when it was a part of my desk. And I could go on to use it to screw a leg onto my couch, at which point that very same screw that was once part of my desk would be part of my couch. The screw is a separable part of each.

So much for what the definition is, and what the various terms used in it mean. Now we begin to ask whether it’s a good definition.

II.

The Adequacy of the Definition. With the definition before us, we can run through various ontological categories, and see whether it gives us the right re-sult. If we find it allows, say, tropes or events to count as substances, we’ll know we’ve got a bad definition.

Condition (i) is that substances are causally efficacious. This condition does two jobs, one minor and one crucial. The minor job is that it helps give a unified explanation of why abstract objects are not substances. We don’t want abstract objects to count as substances, but no other single condition is sufficient to rule out all abstract objects. (Having one condition fully do the job isn’t vital: I shall later use more than one condition to rule out events. But it’s nice to give a uni-fied response if possible.) For example, some abstract objects, if there are such things, might be particulars: say, numbers or propositions.4 Thus, such objects satisfy (iii), so (iii) can’t rule out all abstract objects, even though it rules out uni-versals. Another example: it seems that, say, propositions are non-exemplifiable. Thus, they meet (ii). Another example: while most abstract objects—numbers

3“External and Internal Relations,” reprinted in G. E. Moore: Selected Writings, ed. Thomas Baldwin (London: Routledge, 1993).

4I don’t mean to assert that numbers or propositions are particulars. Here, I am simply avoiding being forced to assert that they aren’t.

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and propositions, for example—cannot be sensibly said to persist, and hence are ruled out by condition (iv), it is at least barely plausible that some abstract objects do persist: for example, a language, or a dance, which come to exist at a particular time, and only last a certain amount of time.5

Now, it may be that things like languages and dances, though they meet (iv), do not meet (ii)—it might be the case that a dance can be exemplified. If that’s right, then it looks like there is some way to rule out pretty much any abstract object imaginable, without needing to bring in condition (i). So it may be that (i) is not strictly necessary to rule out abstract objects. But it is sufficient. And it gives a simple and coherent reason why no abstract objects will make the cut.6 That, in itself, might not be reason to include it. But as I said, (i) does much more important work.

A world with only inert objects—even if those objects are persisting, non-exemplifiable particulars which are not non-separable parts of anything, and which have no separable parts—is a world with no substances.7 The causal efficacy criterion captures a traditional “mark” of substance: substances are active.8 They do things. In short, condition (i) is necessary as a partial account of what substances are really like. Take it out of the definition, and you leave out a crucial element of substancehood. For precisely this reason, traditional Scholastic philosophers argued that occasionalism reduces to pantheism, “for operation follows being; and the mode of operation, the mode of being. If there were only one opera-tion, the divine operation, then there would be only one being; creatures are absorbed into God.”9 This is exactly why certain conceptions of substance as

5These examples are from Chris Swoyer, “Abstract Entities,” in Contemporary Debates in Metaphysics, ed. Theodore Sider, John Hawthorne, and Dean Zimmerman, (Malden, Mass.: Blackwell, 2008), 14.

6It is worth pointing out that I am not here making the claim that the criterion for being concrete is being causally efficacious, or that the criterion for being abstract is being non-causally-efficacious. I am not giving any account of the concrete/abstract distinction here. I am simply supposing that whatever that distinction turns out to be, it will rule that abstract objects aren’t causally efficacious.

7Hence, if “passivism” is true, then there are no substances. Passivism is Brian Ellis’s name for the common modern view that the things in the world are acted upon by outside forces, but are themselves not agents. See, for example, his The Philosophy of Nature (Montreal & Kingston: McGill-Queen’s University Press, 2002), 1–4. Or, for a more full and technical account, see his Scientific Essentialism (Cambridge: Cambridge University Press, 2001).

8As St. Thomas says, “As passive power, or passivity, follows upon being in potentiality, so active power follows upon being in actuality; for everything acts by being in actuality, and is acted upon by being in potentiality.” Summa Contra Gentiles, II, 7. This translation is from On the Truth of the Catholic Faith, book two: Creation, trans. James F. Anderson (Garden City, N.Y.: Image, 1956).

9R. Garrigou-Lagrange, OP, God: His Existence and His Nature, Volume II, trans. Dom Bede Rose, OSB (St. Louis, Mo.: Herder, 1934), 134.

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inert, unchanging substrata for change are so diametrically opposed to the more traditional sort of view I am developing here.10 So (i) is vital.

However, by including it, we do run into an apparent problem. For many think events are causally efficacious. Does (i)—contrary to what we would wish—give us the result that events are substances? No. First, imagine there are instantaneous events: simple events not made up of any smaller temporal parts. If so, then these events do not persist, and hence do not meet condition (iv). Second, any temporally extended event is made up of at least some separable temporal parts, and hence does not meet condition (vi). Or so I claim. For the argument to support this, see the discussion of (vi) which is soon to follow. If that argument is successful, then events—even temporally extended, causally efficacious events—will not turn out to be substances, and so condition (i) brings in the right sorts of things, but, when combined with various other conditions, does not bring in the wrong sorts of things.

To skip ahead one step: part (iii)—the particularity condition—is included principally for a positive, rather than a negative, reason. Its negative role is redun-dant: it does rule out universals as substances, of course, though that work has already been done by (i), for universals are not causally efficacious. But as is the case with (i), (iii) gives an important positive note of substantiality. Substances are not universals. They are particular things.

If there are universals, at least some of them are exemplified by particulars. While Aristotelians may deny the existence of non-exemplified universals, those with more Platonistic leanings may be happy with them. Some of these non-exemplified universals may be exemplifiable. Others may not. Perhaps there is a universal such as square-circleness, for example. This would be a non-exem-plifiable universal. Condition (ii)—the non-exemplifiability condition—tells us that anything which is exemplifiable is not a substance. That, in itself, does not rule out universals as substances, for, as we just saw, Platonists may well believe in non-exemplifiable universals. So the particularity condition steps in here. Because square-circleness is not particular, it isn’t a substance despite be-ing non-exemplifiable. But the particularity condition in itself isn’t enough to rule properties out as substances, for many philosophers believe in particular properties—“tropes.” While the particularity condition rules out universals as substances, it doesn’t rule out tropes. But tropes are exemplifiable.11 So

10On this, cf. W. Norris Clarke, SJ, Explorations in Metaphysics (Notre Dame, Ind.: University of Notre Dame Press, 1994), 102–22.

11Some may think tropes are not exemplified: rather, they are prior to substances, which are themselves effectively reducible to bundles of compresent tropes. Here, I am not ontologically neutral. I take it that substances are not so reducible, and it is simply at odds with my whole project here to so consider them. Needless to say, one can accept tropes without wanting to reduce substances to bundles of tropes. Indeed, I myself tend to believe in tropes while not wanting to

On Substance 31

condition (ii) rules out tropes. So (ii) and (iii) together get us the kind of results we want.

In fact, “exemplifiable” may seem stronger than needed: “exemplified” should do the trick, since it is very plausible that there can’t be such a thing as, say, the redness of this dog, unless the dog is red. If the dog is white, then there just is no such thing as the redness of this dog. Hence, the redness of this dog needn’t be excluded from substantiality, for it’s not there to exclude. We need to exclude the whiteness of the dog, and that it is exemplified is sufficient to do so. Why make (ii) “non-exemplifiable,” then, rather than just “non-exemplified”?

I don’t think this is really an important point, and I’d be glad to make (ii) into “non-exemplified.” But I don’t see a cost in using “non-exemplifiable,” and I do see a slight advantage to it. Some Meinongians might dispute a claim I made in the last paragraph: they might insist that there is a non-exemplified redness trope of that dog. But that redness trope is exemplifiable. If condition (ii) is “non-exemplified,” then it may be that that trope could count as a substance. (It may, however, be that it wouldn’t meet some of the other conditions, such as (iv), but leave that aside for now.) But by making the condition “non-exemplifiable,” I avoid that result.

The only really difficult objection to pose to criterion (ii) is whether, say, the squareness of this circle poses a problem. It is non-exemplifiable: it’s impos-sible for this circle to exemplify squareness. If a Meinongian about tropes is prepared to endorse non-exemplified tropes, why not non-exemplifiable tropes? But it seems quite likely to me that a non-exemplifable trope would fail to satisfy (i)—that is, it would lack causal efficacy.12 Even if that’s not the case, though, the limits of my ontological neutrality have been reached here. That my theory of substance cannot handle impossible properties such as the squareness of this circle is just not something I find alarming.

Condition (iv) tells us that substances can persist. So if there are any essen-tially instantaneous things, they aren’t substances. (Bear in mind the point made in section I: an object may be de facto instantaneous while still being possibly persisting: such an object would be a substance if it met the remaining conditions.) That strikes me as intuitively plausible. An instantaneous object doesn’t have the kind of toe-hold in reality that substances are typically thought to have. Further, if there are any altogether non-temporal things, they are not substances.13

reduce substances to bundles of them. Thus, this condition isn’t pointless.12Thanks to a referee for this point. 13God is thought by some to be “outside of time.” On such a view, he should not be thought

of as persisting. And hence on such a view God would not meet condition (iv), and thus not be a substance. So my definition has an unacceptable result. My reply to this objection: it’s quite right that my definition implies an eternal God is not a substance. I would want no other result. It would be an error to think that you and I and God are all substances in a perfectly univocal

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So much for the first four conditions. The parthood conditions remain. Earlier, I spoke of a desk and its left-hand third. It is plausible, I said, that such parts of the desk are non-separable. Another such non-separable part is—if there is such a thing—the boundary or limit of the desk. One might think that the atoms that compose the desk’s limit are separable from the desk, but the boundary surely isn’t. Thus, condition (v) gives us the right result with respect to limits or boundaries: because they are non-separable parts, they are not substances.

But this may seem like a trick. Consider again the left-hand third of my desk. If it’s removed from the desk, it’s no longer the left-hand third of my desk. But doesn’t it still exist? And if so, isn’t it the case that it can exist and fail to be part of my desk? And if so, doesn’t that mean it’s not a non-separable part of the desk, given my account of non-separability?

One way to see where this apparently damaging line of questioning goes wrong is to focus on the “it” in the question “doesn’t it still exist?” Remove the left-hand third of my desk. Does it still exist? If the “it” refers to the left-hand third of my desk, then the answer is no. If the “it” refers to a chunk of wood, then the answer is yes. The wood survives. But the object it formerly “constituted” does not. So something still exists. But not the left-hand third of the desk. Similarly, if one strips off the atoms that form the boundary of the desk, the atoms still exist, but not the boundary of the desk. (Or, rather, the boundary does still exist, but it remains on the desk: those atoms no longer constitute it.) One way to get some sense of what I’m talking about here is to think of the familiar story of the statue and the lump. Take this clay statue of David. The statue cannot survive being squashed, but the lump can. That is, the statue and the lump have different modal properties (and probably different non-modal properties, too, but leave that aside). Since they have different properties, they must be distinct objects. So if I squash David, is “it” still there? Well, something is still there: namely, the lump. But not David. For David can’t survive being squashed. In a similar way, I claim that when you remove the left-hand third of the desk, while something remains after that change, what remains is not the left-hand third of the desk. That can’t survive removal. (This analogy can’t be pushed too far, of course, since the lump is not part of the statue, nor is the statue part of the lump, and hence neither is a non-separable part of either. So I’m not suggesting the two cases are exactly similar. I’m simply appealing to a familiar picture to help shed light on a less familiar picture.)

sense. My definition of substance shouldn’t apply to him. (Here I echo St. Thomas Aquinas.) As a secondary consideration, it does seem that most philosophical theists these days believe God is “in time,” and that the notion of an eternal God is largely incoherent. Hence this objection is unlikely to worry too many.

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Let me assume for the moment that condition (v) does indeed give the right result with respect to non-separable parts like boundaries. It also gives us the right result from another direction. Assume that you count as a sub-stance. Let’s say you are a part of the faculty of philosophy at the College of Wonderful Wisdom. If so, then you’re a part. So substances can be parts. And a definition of substance should recognize this possibility. And mine does. But notice that your being a part of the faculty of philosophy at the College of Wonderful Wisdom is not essential to you. You are the same person who was once not a part of that faculty, and one day—say, if you retire, or are fired, or leave for another job, or die and yet continue to exist in one post-mortem form or another—you will not be a part of that faculty any more. You’re a separable part of that faculty, and that kind of parthood poses no threat to your substantiality.

A somewhat more serious objection, to my mind, is that it makes sense to think that we are essentially parts of the human race. For one reply to that, see the Appendix, where I argue that human is your substantial kind, and you are hence not a part of the human race, but are, rather, an instance of human. For a reply that doesn’t depend on the notion of a substantial kind, consider what kind of thing the human race is supposed to be (on the assumption that it’s not a substantial kind). The most plausible alternatives are that it is either an abstraction, or it is a very large (temporally and spatially) scattered object.14 If the former, then it doesn’t make a lot of sense to say that you’re a part of it. If the latter, then the dependence runs in the wrong direction, and the objection can’t get going. If the human race is simply an object that is the aggregate of its many human parts, then, like any aggregate, it is posterior to those parts. If there were one more or fewer human being, then the human race would have been a different thing. But you could have existed, if one more human had existed. So you are not a non-separable part of the human race. (It may seem wrong to say that the human race is an aggregate: perhaps it could have had other parts than those it has. But I think that if the human race could have had different members than it has, it’s most likely a substantial kind, and so my reply to that possibility will have to wait for the Appendix.)

Sets may also seem troubling. But only if you consider the members of sets to be parts of the sets. And I, like many others, do not.

The parthood conditions seem to run into trouble of a different kind, though. Go back to the example of the desk we looked at a few paragraphs ago. I argued that the desk has some non-separable parts, such as its boundary and its left-hand third. But it is very plausible that the desk also has many separable parts.

14For interesting discussion of this sort of question, see Kathrin Koslicki, The Structure of Objects (Oxford: Oxford University Press, 2008), 219–34.

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For example, the screw that holds the left front leg on, or the atoms that compose the boundary. It seems obvious that those atoms—the very same atoms—can exist as parts of the desk, and remain in existence in separation from the desk. Those atoms are not internally related to the desk: it is not essential to them to be part of the desk. If this is right, then the desk wouldn’t make the cut as a substance, for it wouldn’t be the case that it had no separable parts. Some might see this as a problem for my account. After all, many philosophers introduce the notion of substances by listing some examples, and they typically point to ordinary objects like cats and dogs, desks and cars as their examples.

However, I fail to see this result as a problem. For me, this brings out one of the primary desiderata in an account of substance: namely, preserving and accounting for the difference between substances and non-substantial objects such as the desk, or Mount Everest. The parthood conditions bring out the distinction. Plausibly, Mount Everest is a non-separable part of the earth. If the mountain were uprooted by a giant, tossed out of the earth’s atmosphere, and left to simply float around in outer space, it wouldn’t be Mount Everest anymore. The rocks that composed Mount Everest (along with their parts, and their parts, etc.) might remain self-identical through that change, but Mount Everest itself wouldn’t. Being a mountain involves having a certain kind of rela-tion to a landscape.

Now, I do think the desk would remain what it is even if it were tossed into outer space. It’s not clear that the desk is a part of anything. Unrestricted compositionalists will disagree, but the point isn’t essential to my case. What’s really essential is the other side: things like Mount Everest, and my desk, all have separable parts. Indeed, it looks as though they are all built up out of parts—parts that are prior to them. Objects like my desk are derivative, posterior, things. Their separable parts are prior. The atoms the desk is made of are the really real things here: the desk is just a supervenient thing. The way (alleged) desks pig-gyback on their parts for their existence has led some philosophers to deny they exist at all. I don’t say this. I just say they are not substances. And the reason I say this is that desks aren’t fundamental things. They’re too dependent, too second-hand. Their parts, at some level of decomposition, do all the work we attribute to desks. Their parts are the substances. Desks are just free riders. In other words, the parthood conditions get at the vital notion of fundamentality. Substances are fundamental things: they are not derivative. They are primary, not posterior. This is connected to the causation point, as I hinted just above. It’s the fundamental objects in the world that do the work. The derivative objects come along for free.

So I am invoking notions of priority and posteriority. Here is a nice state-ment of what I’m getting at: “What is posterior is dependent on, grounded in, explained by, reducible to, existent in virtue of, and nothing over and above,

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what is prior.”15 There is trash scattered in my driveway. I sweep the bits together into a pile. The bits are prior to the pile: the pile is dependent on, grounded in, explained by, reducible to, existent in virtue of, and nothing more than what is prior to it: namely, its parts. The pile of trash isn’t a substance. But the desk is posterior to its parts in exactly the same way as the way in which the pile of trash is posterior to its parts. And so neither is it a substance.

Notice what my position does not entail. It does not entail that no substance has any (material—I leave aside the issue of temporal parts for the moment) parts at all. One way to have no separable parts is to have no parts at all. Another way to have no separable parts is to have only parts that are non-separable. If there were an object that met the other conditions in the definition, and had parts, but only parts like the left-hand third of the desk—parts that are internally related to it—then that thing would be a substance. Think of the parts of an organism—my liver, for example. If you remove my liver, then it is no longer a liver. (You might not agree with this, but for the moment I am just using it as a dispensable example. It is, however, a view that traces back to Aristotle, and is hence venerable, in addition to being true.) The liver, once removed, becomes a pile of tissue, which is only homonymously a liver, just as the “eye” of a statue is only homonymously an eye. This is because my liver is internally related to me. It cannot survive being removed. Something survives, namely, the matter.16 But the liver does not. If all of our parts, including our atomic parts, were like that, then we would be substances, despite being complex, spatially extended objects. I will have more to say on this point in the next section. Before I move on to that, I have to turn back to temporal parts.

Think again of the pile of trash. Each of the parts of the pile—say, this empty soda can—is, if the defenders of temporal parts are correct (and here I

15Jonathan Schaffer, “Monism: The Priority of the Whole,” Philosophical Review 119 (2010): 31–76.

16I hereby admit that I am invoking the Aristotelian notion of prime matter. I find this notion to be not only necessary philosophically, but also comforting. Others, much to my chagrin, find it wildly implausible and verging on (or, indeed, well into the realm of the) unintelligible. For such philosophers, I have the following to offer: one needn’t accept prime matter to endorse my theory of substance. One can, instead, accept the now fairly common notion that material objects can simply pop into and out of existence. (That this is impossible provides a key premise in a central Aristotelian argument in favor of prime matter, found in Physics I, 8.) The philosophers most likely to endorse the notion of material objects simply popping into or out of existence are those who endorse constitutionalism: the idea that, say, a human person is a material object constituted by a human organism. Such philosophers are likely to believe that the human person pops into existence when the young human organism develops sufficient mental capacity to constitute a person, and that it pops out of existence when the human animal loses such capacity. (Chances are that they won’t actually say it that way, but that is what they’re committed to.) So if your animal is gravely injured, suffering irreversible brain damage such that it can no longer think in a characteristically human way, then you cease to exist. Where’s your corpse? Nowhere! You’re just gone.

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ignore the spatial parts of the can for simplicity’s sake), dependent on, grounded in, explained by, reducible to, existent in virtue of, and nothing more than their temporal parts. The can has a history stretching from the time a certain bit of metal was molded into can form, to the time the can gets melted down again. The can is just made up of the many temporal parts of its lifespan.17 It is pos-terior to them. This point seems to generalize. The perdurantist ontology, in its typical form, considers that any filled region of space-time contains an object: you have your little bits—the temporal/spatial parts—and then you have the objects composed of them. Which bits compose objects? All of them! On this view, every object except the indivisible smallest temporal parts—if there are such things—is derivative; things like you and me are aggregates of ontologically prior temporal parts. These parts, then, are separable. Perduring objects—things that persist via having different temporal parts located at different times—are not substances, on my definition of substance.

But it is hard to see how things are otherwise with events.18 (It may be that defenders of temporal parts who believe in substances can’t—or would prefer not to—distinguish between events and objects. I’m ignoring that point, since if they deny the distinction I’ve already responded in full to them in the previous paragraph. If, however, they prefer to make the distinction, I need to say some-thing about events.) The temporal parts of events are events. The orbiting of the earth around the sun is an event composed of “smaller” events, such as the earth moving from point A to point B. The larger event—the orbit—is just made up of those smaller, separable events. And so this event is not a substance.19

17Here is one account of what it is to be a temporal part. X is a temporal part of y at t = df. (i) x exists at, but only at t, (ii) x is a part of y at t, and (iii) x shares a part at t with everything that is a part of y at t. See Thomas Crisp and Donald Smith, “‘Wholly Present’ Defined,” Philosophy and Phenomenological Research 71 (2005): 318–44, at 323. So here we see how the temporal and spatial parts of the can are layered in such a case that the can’s temporal part at t shares a part with all of the can’s spatial parts at t. So strictly speaking the can isn’t just made of its temporal parts, but also all those spatial parts that it shares with its many temporal parts.

18In what follows, I leave aside the priority monist view, which could very well be used to make sense of the claim that events are prior to their parts. That would also apply to the discus-sion of temporal parts in the preceding paragraph. On priority monism, see Schaffer, " Monism," 31–76. Monists who deny the parts of the whole exist at all obviously wouldn’t be inclined to argue that the whole is prior to the part.

19Another way to rule out events as substances is to invoke a fairly standard move and claim that events occur, while objects exist; and then to make it part of my definition that substances exist, rather than occurring. I have doubts about the wisdom of such a move, for it seems obvi-ous that, if there are such things as events at all, then they exist. I would be inclined to say that a difference between substances and events is that the former subsist, while the latter do not. But since subsistence is the mode of being had by substances, I can hardly invoke subsistence in my definition of substance.

On Substance 37

It might be objected that some events do have non-separable parts. Consider a baseball game, where the event of my throwing a strike can’t be separated from the game: if you pull that event out of the context of the baseball game, it’s just not an instance of throwing a strike. That’s true: but it is not the case that no part of the baseball game is non-separable. For example, the event of my catch-ing the ball would not be an instance of the batter’s being out, if it’s removed from the game. But it would still be an instance of my catching the ball, even moved out of the game. The catching of the ball, the throwing of the ball, the swinging of the bat, etc.: these are all separable events that are temporal parts of the larger event. So the larger event is not a substance. It seems to me that the same point will be able to be made with respect to any event.20

Similarly, one can use this criterion to rule out privations as substances. I suspect one can also use condition (i) to rule out privations, since if there are such things as privations—for example, the hole in a donut, or a shadow—then it would seem they are non-causally-efficacious. However, some have suggested that absences can be causes.21 Even if they’re right about that, privations can still be ruled out, because as far as I can make out, privations have separable parts. Here, I follow Hoffman and Rosenkrantz, who argue that the parts of priva-tions are places and/or times.22 Take the donut hole. Its parts are places. If the donut is moved, the hole goes with it, but the places don’t: it gets new places as

20I pass over important disputes regarding the individuation of events. Some might say that the catching of the ball is identical to putting-out-the-batter. And so if the one is non-separable, the same is true of the other. (Defenders of events as individuated via spatio-temporal “location,” such as the later Davidson, would take such a line.) I find certain objections to such an account decisive, such as Davidson’s own example of the spatio-temporally identical warm-ing and spinning of a metal ball: the warming and the spinning seem obviously distinct events despite their spatio-temporal identity. And hence spatio-temporal identity is not an adequate way to individuate events. I do not myself have a theory of event individuation to offer, although I’m inclined to a property exemplification account (which would, at least according to certain conceptions of properties, get me the result I rely on above, although its getting me that result is not the reason I’m inclined to endorse it). So I here simply flag the fact that my argument depends on admittedly controversial assumptions about events. Note that all this could be avoided by denying that events exist at all, which is another view I incline towards. (Though the times at which I incline towards this are not identical to the times at which I incline towards Kim’s account.)

21Even Aristotle said something that can be taken in that way, when he said that the absence of the pilot is a cause of the crashing of the boat (cf. Metaphysics, 1013b 12–16). Whether he really means that in a strict way is questionable. But neo-Humean accounts of causation can pretty clearly be squared with the notion that an absence can be a cause. So much the worse for neo-Humean accounts of causation, I would say. But as above, I don’t want to delve into a deep account of causation in this paper, so I prefer to go another way with the privation problem.

22Joshua Hoffman and Gary Rosenkrantz, Substance: Its Nature and Existence (London: Routledge, 1997), 68–9.

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parts. But the old places remain self-identical through this change. (I mean, the change from being a part of a donut hole, to not being a part of a donut hole.) They are separable. And hence the privation is not a substance.

One last, but very important, consideration: it is often thought that “sub-stances” are bundles of universals, or that they are bare substrata (or bare substrata taken together with the properties that inhere in them). There are, I think, com-pelling arguments against such views.23 It would be nice, then, if my account of substance ruled out substrata and bundles. And it does. Take the simplest case: imagine you think that a substance is a bundle of universals. Those who endorse such a view will say that the substance’s properties are parts of the substance. But if red—the universal red—is a part of this red thing, then of course that thing has a separable part, and hence is not a substance. Precisely the same point holds with regard to substratum theories which make the substance identical not to the substratum itself, but to the substratum plus the universals that inhere in it. (It is possible to hold that the substance is simply the bare substratum, which is how the substratum view is sometimes interpreted: such a view is inconsistent with the causal efficacy condition, for a property-less substratum can’t be taken as causing anything.) Trope theorists are in the same boat, however, as long as they endorse the common view that it is metaphysically possible for tropes to float free of their substances.

One trope-theoretical bundle theory that might seem to escape this objec-tion is Peter Simons’s nuclear theory, according to which substances are two-tiered bundles: a “nucleus” of co-dependent tropes, and a perimeter of tropes dependent on the nucleus.24 As I understand his account, none of the tropes in such bundles are separable parts. However, as Simons notes elsewhere, “everyday substances” (like you and me) will, on his theory, be more than just one such bundle: “only objects without parts in the common or garden sense [i.e., objects with no parts like legs or arms or molecules: objects, that is, with only properties as parts] are pure bundles of tropes and nothing else.”25 So everyday substances like you and me have, say, water molecules as parts. It is part of Simons’s view, as I under-stand it, that such parts are separable from the larger bundles. Hence you and I have separable parts, and turn out insubstantial according to my definition. (Tu quoque: my theory already rules that desks aren’t substances, and so is inconsistent with everyday “substances” counting as substances! I’ve already explained why

23See, for example, Hoffman and Rosenkrantz, Substance, 26–42; Michael Loux, Substance and Attribute (Dordrecht: Reidel, 1978), chaps. 6–8.

24Peter Simons, “Particulars in Particular Clothing,” Philosophy and Phenomenological Research 54 (1994), 553–75.

25Peter Simons, “Farewell to Substance: A Differentiated Leave-Taking,” Ratio 11 (1998), 235–52, at 244.

On Substance 39

this isn’t troubling; further, as I’ll explain in section IV, my theory is consistent with you and me counting as substances.)

So my definition rules out Simons’s bundle theory—at least in the case of macrophysical substances. If there are fundamental Simons-type bundles somewhere down there—a claim my view is not committed to (for I have fun-damental substances all over the place, and hence needn’t posit some ultimate particles)—then it may turn out that my view would rule such bundles as substances. I find this unproblematic: as Simons himself points out, his view is quite similar to an Aristotelian theory of substance when we come to the fundamental things. But it’s not clear why one would be drawn to a Simons-type theory anyway, given that it’s not going to be able to provide a unified account of substance. One could adjust Simons’s bundle theory in such a way that macrophysical substances like you and me are bundles with no separable parts, thus yielding such a unified account, while counting us as substances. If one did that, there would be a bundle theory consistent with my view. I do not know why such a theory would be preferable to, say, Michael Loux’s account of substantial kinds.26 But that such a bundle theory would be consistent with my account of substance is, again, untroubling.

That covers the kinds of things that need to be ruled out. On the positive side of things, the definition rules that angels and Cartesian souls—if there are such things—are substances. For such things would be persisting, causally efficacious, non-exemplifiable particulars which are not non-separable parts of anything, and which have no separable parts. This is a good result, for while many philosophers do not believe in such things, it does seem obvious that if there were angels or Cartesian souls, they would be substances.

III.

Reply to Objections (1). My view faces at least two objections that look very serious. In the next two sections, I present and reply to these objections.

First, the definition looks thrown together. It’s just made up of a bunch of unconnected ideas: it’s not unified in any important way. Further, it might be taken to violate what seem to me to be very sensible constraints on defini-tions: it might seem ad hoc—that is, it might seem to include certain elements simply in order to rule out counterexamples—and it might seem negative where it should be positive.27

26Michael Loux, Metaphysics, 3rd ed. (London: Routledge, 2006), chap. 3.27For the quick but helpful discussion of definitions from which I draw these latter two

points, see Linda Zagzebski, Virtues of the Mind (Cambridge: Cambridge University Press, 1996), 264–5.

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It’s true that certain elements in the definition are included in part to exclude counterexamples. If I didn’t specify that substances are able to persist, for example, then it might turn out that an instantaneous event counted as a substance. That would be a bad result. It’s also true that certain aspects of the definition are negative. “Non-exemplifiable” is clearly a negative element, for example. It’s also true that my definition brings together a good many apparently diverse and unrelated elements, without providing, on its face, any clear link between them all (other than that they’re jointly necessary and sufficient to get the right result, which I take it is a pretty strong point in favor of the definition!). So this objection has significant prima facie force.

Here is why it fails. The definition’s various elements are tightly unified, in virtue of together yielding a positive account of substance that is, moreover, an elaboration of a traditional view. The view is, roughly, Aristotle’s, but my more proximate influence is St. Thomas Aquinas. A standard way of putting the view is that substances are those things in which properties inhere, but which themselves do not inhere in anything. This is a fairly negative account, of course, so a more positive take is that substances are those things that exist in themselves. Accidents are then defined as those things which naturally inhere in something else. This is, effectively, Aristotle’s famous “neither said of nor in” account of substance from the Categories. The account has been attacked by Hoffman and Rosenkrantz28 (among others) and seems hard to defend as it stands. However, such objections can be avoided by taking the central idea of the account and translating it into my definition. All the elements in my defini-tion serve the purpose of cashing out this notion of substance in its full sense. (That is, including the various “marks” of substance that Aristotle explains in chapter 5 of the Categories, such as, most relevantly, that substances can undergo intrinsic change.)

The notion of substance as bearer of properties is suggested by the notion of substance as causally efficacious, for the way in which it will cause things is via exhibiting certain (rather than other) properties. The related Aristotelian notion of substance as things that can change comes with the causal efficacy condi-tion, too, for (with one exception) all movers that cause motion are themselves in motion (which is to say, are changing). Thus, while I do not claim a strict implication from being a mover to being moved, I do claim a close relation. Being possibly persisting also ties in here, for only if it can persist, can it change. My definition also claims that substances are non-exemplifiable and particular. When we conjoin these points with the result that substances are the bearers of properties, we will find that my definition gives the result that substances are bearers of properties but not themselves properties.

28Hoffman and Rosenkrantz, Substance, 14–6.

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If we want to explicate an Aristotelian account of substance, we need to make causal efficacy part of our account, even though Aristotle himself doesn’t specify it as an element, because substances are those things with natures, which is to say things that do certain characteristic types of things.

The claim that substances are causally efficacious also links up to the “no separable parts” bit, as the latter is the best way to account for the former. To see this in full, we would need to spend a few pages considering Trenton Mer-ricks’s Overdetermination Argument for eliminativism, and I think it best not to include that discussion here.29 But in brief, the argument is that there can’t be macrophysical objects such as baseballs and chairs, because if there were such objects, they would cause things; but since the parts of (alleged) baseballs cause all the things baseballs are thought to cause, baseballs don’t cause anything. Therefore, etc. This argument might seem to apply equally to humans: Merricks offers a complicated way to avoid eliminating us.30 But a less complicated way to avoid eliminating us is to claim that we have no non-separable parts, and hence don’t compete with our parts when we try to cause things. This, then, explains why substances cannot be non-separable parts of other substances (and hence the inclusion of the last element in the definition). For if they were, then they would compete with that substance in causing things, leading us to eliminate the substance of which they are parts. (More on this in the following section.)

Further, the traditional account of substance sees substances as both fun-damental and unified. My definition gives an account of both of these aspects of substance: they are fundamental in the sense of not being made of things that are prior to them, and they are unified in the same sense. So the “no separable parts” condition does lots of important work.

While my definition sounds novel and rather hodge-podge, it’s really a tightly unified way to cash out a standard notion of substance while not mak-ing (many) controversial assumptions about what there is. I have not given a particularly lengthy account of all this here simply because my paper is too long even without that, and most readers may not think it all that important that I can show that my account links up with Aristotle’s in every detail. I am hoping that what I’ve said is, however, sufficient to show that the definition is both positive and unified.31

29But see my “Emergent Substance,” Philosophical Studies 141 (2008): 281–97, for a full discussion.

30For all this, see Trenton Merricks, Objects and Persons (Oxford: Clarendon Press, 2001).31There are other ways to try to shore up an Aristotelian account of substance, of course.

One such way is developed by Michael Gorman in “Independence and Substance,” International Philosophical Quarterly 46 (2006): 103–18. Gorman’s account has some weaknesses, however; the most significant of which is that it requires an account of essence that departs pretty radi-cally from the standard modal account. Further, it’s not at all clear that it avoids the kind of

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IV.

Reply to Objections (2). Here is a second objection. Perhaps it is believable that things like desks or solar systems aren’t substances: but my definition yields the conclusion that organisms aren’t substances, either. For it surely seems that we have some separable parts. (For example, our atoms, among other things.) Now there is no point at all in producing a theory of substance that gives the result that you and I aren’t substances. Lists of objects that, intuitively, fall under the concept of substance always begin with organisms—these are substances, says Aristotle, if anything is! But, in fact, this problem is not serious.

First, it is just false that my definition entails that we aren’t substances. What it entails is that either (a) we aren’t substances or (b) we are immaterial substances like souls or (c) we are material substances with no separable parts. I accept (c), and here I want to suggest that (c) is not all that hard to believe. In fact, there are very strong, independent reasons for endorsing (c).

Consider again the example of my liver. It is plausible that the liver is internally related to me, such that if it is separated, it ceases to be what it was. It is a non-separable part. I say this is plausible: that is, of course, very different from saying it’s the only sensible thing to believe about the ontological status of my liver. I’m not trying to prove it is non-separable. I’m only suggesting that it makes sense to say that it is. It makes sense to say that part of what it is to be a liver is to play a certain kind of role in an organism, and that when some-thing no longer plays that role, it is no longer a liver.32 Although we refer to a detached liver as a liver, in doing so, we use the term equivocally. In the case of the organism and the liver, the organism is prior, not the liver. The whole is prior to its part.

Again, the trouble for my view is with things like atoms. Here is how the problem goes. Take this carbon atom here. It is part of me. If we traced out its life history, we would see that it became a part of me a week ago. Before that, it was part of a cow. If we continue to follow out its history, we’ll see that it will cease to be a part of me several weeks down the line, as the skin cell that it is part of dies and falls off me. Perhaps it gets eaten by a dust mite, and becomes part of it. That atom—one and the same atom—was first part of a cow, then part of me, then part of a dust mite. This means it was a separable part of me. Thus, I have separable parts. Thus, if my definition of substance is correct, I am not a substance.

This is too quick. Why say that the atom we’re talking about is a separable part of me? If we deny that it is a separable part, then we save ourselves any

objection I’m dealing with in this section any better than my definition does. 32See Michael Loux, Metaphysics, 117.

On Substance 43

number of serious ontological headaches. For a full account of this, see my previously-cited paper.33 But here’s a quick example. Think of the “Problem of the Many.” That problem goes like this: here in the vicinity of my chair are many millions of atoms. Plus me. I am made out of these atoms. But which ones? Some of these atoms are clearly within my boundary. Some of the atoms are clearly outside my boundary. But many, many atoms are neither clearly in nor clearly out. There are many equally plausible ways to draw my boundaries: many aggregates of atoms seem to have equal claim to composing a human animal. Do they each compose a human animal, making it the case that there are hundreds or thousands of animals in my chair? Or perhaps, because there are so many equally strong candidates for composing a human animal, we have to rule that none does—that I do not exist at all?34

To put this another way, imagine you mark out all the atoms that compose me at t1, and call those atoms the As. (This assumes, for the sake of argument, that there is some determinate group of atoms that compose me at t1: in other words, this way of framing the problem is most favorable to someone who wishes to solve the Problem of the Many. In what follows, I’ll show that my view gives a principled reason for claiming that there must be a determinate group of atoms—or whatever else—that compose a material composite substance.) Now, mark out one of these atoms: this one here, at the tip of my finger. Call that atom B. The As compose a person at t1. But it seems the As minus B compose a person at t1, too. After all, if you remove B at t2, then the As minus B would surely still compose a person at t2. So why not at t1, as well? Hence, there are two equally good candidates for being a human person here within my borders at t1. And there is nothing special about B. The same point can be made with respect to any of my atoms. So there are a great many equally good candidates for being human persons here within my borders at t1.

This is widely taken to be a serious problem. Indeed, it has prompted some philosophers to eliminate themselves, and others to immaterialize themselves. But these extreme reactions are unnecessary. In comparison, my own response is admirably conservative. It goes like this. The As minus B at t1 are not a substance, but I am. However, the As minus B at t2 are a substance, as am I. That’s because the As minus B are identical to me at t2, while at t1 they were not. The Problem of the Many gets its grip on us by pushing us to think that the As at t1 are in the same boat, ontologically speaking, as the As minus B (at t1). But that’s not so. The As minus B (at t1) are a part of a substance. They’re the vast bulk of the substance, to be sure, but still not the whole of it. And since the As minus B

33Toner, “Emergent Substance.”34D. Lewis, “Many, but Almost One,” in Ontology, Causality and Mind: Essays in Honour of

D. M. Armstrong, ed. John Bacon (New York: Cambridge University Press, 1993), 164.

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(at t1) are a part of a substance, they’re not themselves substances, nor do they compose a substance. The substance—me—is (at t1) composed by the As.35

As I said earlier, this view shows that there is an answer to the question of which atoms compose me at t1, as well. We can’t tell the difference between the atoms that are my parts, and those that aren’t my parts, by looking at them. But in fact their identities either are caught up with mine, in which case they’re my parts, or are not, in which case they aren’t my parts. I’m not giving an epistemic criterion here: we have no way to tell just by looking whether a given atom is part of me or not. I’m simply saying that there is a fact of the matter. If the atom is my part, it is a non-separable part. I have parts that, so to speak, look and act just like carbon atoms. But they’re not (univocally; see next paragraph) carbon atoms. For carbon atoms are substances, and none of my parts are substances.

So my view carries a lot of philosophical weight: in addition to handling the Problem of the Many, it offers an easy response to the Vagueness Argument for unrestricted composition, the Overdetermination Argument, and the Prob-lem of Material Composition.36 Those are serious points in its favor. Moreover, we do not need to say anything crazy to endorse my view. We can still truly, though non-univocally say that I have carbon atoms as parts, just as we could say, non-univocally, that there is a liver on the table. We do so by invoking the distinction just made. Carbon atoms, classificatorily speaking, are substances. When a carbon atom becomes a non-separable part of me, it is (by condition (v)) not a substance, and hence not classificatorily a carbon atom. But just as the liver on the table is not classificatorily a liver (because being a liver involves in part playing a certain role in an organism), but can still be called a liver, my carbon-atomish parts can still be called carbon atoms: they are nominally carbon atoms. Everything we want to say about the work that gets done in organisms because of carbon atoms can all still be said. We just can’t endow such claims with too much metaphysical baggage. This is fine, since we shouldn’t endow them with too much metaphysical baggage. We’re talking about scientific claims: it is a scientific claim that I have carbon atoms in me. The scientist qua scientist doesn’t get to say that those carbon atoms are substances, or that the carbon atom that is a part of me now is numerically identical with the carbon atom that’s going to be part of a dust mite in a few weeks. Those are philosophical claims.

35A funny objection: the As minus B are part of the substance. But they’re a separable part, since they can be removed and still survive. That is, by removing B from the As, we’ve removed the As minus B from the As, too. This is a funny objection, but not a serious one. What counts as removing a part must be guided by whether the substance survives it. If we cut off my arm, we haven’t removed the arm complement from the whole, we’ve removed the arm from the whole: that’s the proper description of what’s happened.

36For a full defense of these claims, see Toner, “Emergent Substance.”

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Further—and this is important—it is no part of my view of substance to claim that only substances exist. I’m not saying desks don’t exist (just that they’re not substances), and I’m not saying that the parts usually called “carbon atoms” in you don’t exist (just that they’re not substances.) This is not a form of eliminativism.

To take stock: if we endorse the claim that substances have no separable parts, then we can do some really important metaphysical work, without re-ally giving up anything important. Moreover, the philosopher who refuses to be convinced that it is in any way sensible to think that you and I have no separable parts is insisting that you and I are not fundamental objects. Such a philosopher is insisting, in effect, that our atomic parts are prior to us. That makes us posterior, in much the same way that the pile of trash is posterior to the pieces of trash. Now, I can understand someone taking such a view: it is a nicely reductionistic sort of view and has impressive empirical credentials. I have no quarrels with such a view (aside from thinking it’s false). But what I can’t understand is why such a philosopher would be troubled by the implication of my definition that you and I are not substances. If you want to tell such a reductionistic story about us, why are you fighting so hard to claim that we are substances? Why not just accept that we aren’t substances, any more than the pile of trash is a substance?

What I want to suggest is that my definition of substance poses an alter-native, and while I can’t offer compelling reasons to go one way rather than the other, I do think it is fair to say that neither alternative is really untenable. The alternatives are: (1) either you and I have separable parts and hence aren’t substances, or (2) you and I have no separable parts (along with meeting the other criteria) and hence are substances.37 Imagine you take as indisputable the idea that we have separable parts. Then, it seems to me, you shouldn’t be upset at giving up the idea that we are substances.38 Imagine, instead, that you take as indisputable the idea that we are substances. Then, it seems to me, you shouldn’t be upset at giving up the idea that we have separable parts. It seems to me that those are natural pairs of views. That my definition brings out those pairings seems to me a virtue of the definition, not a vice. I don’t say it’s impossible to believe that we are substances and that we have separable parts, of course. But it strikes me that there’s a real tension in that view.

37This alternative could be subdivided: either we are physical or nonphysical objects that lack separable parts. I am, of course, urging the former.

38If we are not substances, what are we? I don’t know. A logical construction out of atoms or something like that, I suppose. Maybe you can say something interesting here, but why would you want to? This problem is one of the main reasons I endorse my view. And so should you. Because you are obviously a substance.

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So I submit that my account of substances does what we want, and doesn’t do what we don’t want. I commend it to you for your consideration.39

Wake Forest University Winston-Salem, North Carolina

Appendix

In the Aristotelian tradition, it is common to speak of the kinds under which things fall. Since I count myself as someone who belongs to that tradi-tion, I want to briefly offer an alternative definition of substance which brings the notion of substantial kinds into play. The definition of substance becomes quite easy on this approach:

X is a substance = df. X is an instance of a substance kind.

The tricky part, then, is to say what counts as a substance kind. Before doing that, I will say what a kind is, in general.

X is a kind = df. X is a universal and, possibly, for some y x marks y out as what y is.

To “fall under a kind” is to be marked out as what one is by that kind: things that fall under a kind are an instance of that kind. Those who object to uninstantiated universals can drop the “possibly.” Note that the y needn’t be a particular. It can be any sort of thing, including a universal. The universal yellow (if there is such a thing) is marked out as what it is by its kind, namely, color. That means, at least, that being a color is essential to being yellow.

Last, the notion of a substantial kind:

39I do not wish to sidetrack the paper by going into objections that will be of interest to only a small number of readers. But there is one point I wish to touch on. Those with hylomorphic inclinations might argue that the soul is a separable part of the human being. When I die, my soul will persist, and it will be the very same soul then, that it is now. And hence I have a separable part and am not a substance. As a hylomorphist, I regard this as a very serious objection indeed, and I hope to address it in detail elsewhere. Since, however, hylomorphism remains (sadly) a view endorsed by a tiny minority, I believe it best to pass over the objection mostly in silence here. A full response would require an awful lot of technical wrangling that would likely not be of much interest to most readers. But very briefly, I’ll mention two moves the hylomorphist might make. First, she might claim that the persistence of your soul is sufficient for your persistence, and hence that your soul is not a separable part of you. Alternatively, she might press very firmly on the distinction between “metaphysical parts” and “integral parts.” The upshot would be that my definition would have to be altered to make it clear that the kind of parts in question in (v) and (vi) are integral parts, while the soul is a metaphysical part, and hence not a counterexample. For now, I shall let the matter rest.

On Substance 47

X is a substantial kind = df. X is a kind and for any y that falls under x, y is a (i) persisting (ii) causally efficacious (iii) non-exemplifiable (iv) par-ticular which (v) is not a non-separable part of anything and (vi) has no separable parts.

As I mentioned in the body of the paper, since I am an instance of human, it makes no sense to think of me as being a non-separable part of the human race: the human race is just all and only those things that are instances of hu-man. If there is such a thing as the human race, then its parts don’t derive its identity from it, but, rather, they derive their identity in virtue of being instances of human, and then the human race derives its identity from them. They are prior to it. I don’t think it is necessary to invoke this point to handle the objec-tion, since I believe it was already dispatched in the main text. But it is worth pointing out anyway.

Talking in terms of substances as instances of natural kinds allows us to do other sorts of work, much of which isn’t particularly relevant here.40 I prefer not to complicate the argument of this paper by going into natural kinds in detail. However, I’ll give two brief considerations in favor of making the move to the natural kind account of substance.

First, it unifies the account of substance by placing substances within a category—the substance kind—but without embroiling that category within a highly debatable system of categories. This is a significant advantage of this kind of view over that of Hoffman and Rosenkrantz, whose view requires acceptance of their categorical scheme. But why think their categorical scheme is right? There are plenty of others on offer.41 And without feeling confident that the categorical scheme is correct, one simply cannot find their view of substance satisfying.42 Needless to say, I am not suggesting that my view doesn’t involve some highly controversial claims. However, the claims it involves seem evaluable in a more straightforward way than the large-scale theorizing involved in setting forth a whole categorical scheme. I suppose this is debatable.

Second, it makes the distinction between substances like you and me, and artifacts like my desk, more obvious. (To my mind, at any rate.) For, as I would argue were this a paper about natural kinds, it follows from the account I’ve given

40Centrally, the notion of a substantial kind must be invoked to solve certain problems for transubstantiation. See my “Transubstantiation, Essentialism and Substance,” Religious Studies (forthcoming).

41For just a couple of examples, see Roderick Chisholm, A Realistic Theory of Categories (Cambridge: Cambridge University Press, 1996), and E. J. Lowe, The Four-Category Ontology (Oxford: Oxford University Press, 2006).

42This point was made by Trenton Merricks in his Review of Substance Among Other Cat-egories, Philosophy and Phenomenological Research 57 (1997): 480–2 at 482.

American Catholic Philosophical Quarterly48

that natural kinds will be governed by laws of nature in ways that artifactual kinds aren’t. The laws governing the desk govern its substantial parts, not the desk itself. But the laws governing the behavior of substances apply to the substances directly. (At least, that’s the claim, which I cannot defend here.) So I think putting the notion of substance in the light of natural kinds helps undermine worries about my account from the distinction between desks and humans: it would also help settle questions about just what things are substances. Desks, no. Earthworms, probably. Water molecules, probably. Humans, definitely. Etc.