Philos Stud (2010) 148:125–132 DOI 10.1007/s11098-010-9499-y

Reply to my critics Sydney Shoemaker

Published online: 23 January 2010 Ó Springer Science+Business Media B.V. 2010

I want to thank Louise, Andrew and Jaegwon for their very helpful comments. They have given me a lot to think about. Jaegwon’s comments address my overall strategy, so I will begin with them. At the end of his comments Jaegwon poses a dilemma: either my physicalism doesn’t count as physicalism, or it is a version of reductionist type physicalism. I certainly regard myself as a physicalist, and I think I accept the ‘‘starkly physicalist’’ picture Jaegwon finds suggested by some of what I say. I think that mental properties are physical in the same sense that automotive properties, architectural properties, computer properties, and botanical properties are physical. I would express this sense by saying that instances of all such properties are physically realized—they are both property-realized in accordance with my subset account, and realized in microphysical states of affairs in the way I spell out in Chapter Three. What matters for physicalism is that the actual world instances of these properties are physical, and it is sufficient for that that these instances are physically realized. What Jaegwon sees as clashing with physicalism is the distinction I draw between the mental causal features of properties and the physical causal features of properties. Here my terminology was misleading. I didn’t mean to imply that the mental causal features are non-physical. Let’s say that mental properties are a class of physical properties. The mental causal features of a property are those specified in terms of the effects on the instantiation of properties belonging to this class. And what I called the physical causal features are those specified in terms of the effects on the instantiation of physical properties not belonging to this class, e.g., physiological properties. As for whether my physicalism is reductive type physicalism, I think that it isn’t—while I hold that all actual world realizers of mental properties are physical, I am not committed to mental properties being necessarily such that they can only be realized physically, for I am agnostic about S. Shoemaker (&) Cornell University, 104 Northway Road, Ithaca, NY 14850, USA e-mail: [email protected]

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whether there are dualist worlds in which mental properties have nonphysical realizers. For the same reason I am not a reductive type physicalist about automotive properties and botanical properties. Jaegwon sees me as pitting my subset account of realization against the standard second-order properties view. This isn’t quite right, because I say in my book that the subset view can be regarded as a special version of the second-order properties view. It differs from other versions in characterizing the relation between the second-order property and its realizers in terms of a relation between their causal profiles, thereby implying that the realized property, the second-order property, has a causal profile of its own. This is in opposition to versions of the view that hold that whatever causing is done is done by the first-order realizers and not by the realized property. Jaegwon finds a ‘‘bit of a problem’’ with my philosophical strategy here. He says that ‘‘merely to point out that the second-order account leads to a philosophically unpalatable consequence is not enough, in itself, to condemn it. Maybe we have to swallow some unpalatable consequences of our assumptions and presumptions’’ (p. 5). But it is not the second-order account generally, but only versions of it that have the unpalatable consequence, that I condemn. What Jaegwon really finds ‘‘troubling and worrying’’ (p. 8) is my ‘‘starting assumption’’ that mental properties have causal powers, indeed physical causal powers. But again I fail to see what is objectionable about my strategy. We do regularly give causal explanations that invoke mental states as causes of both other mental states and of behavior, and surely there is a presumption in favor of a view that makes this legitimate. Of course, if this assumption turns out to conflict with things we have good reason for believing, we will have reason question it. My aim in my book is to show how we can give an account that makes this presumption which accords with our intuitions and does not lead us into this sort of trouble. Jaegwon is of course right to say that there are various considerations that can seem to lead to epiphenomenalist conclusions, and he cites the fact that if we trace the history of a hand movement that is ascribed to pain we will ‘‘end up with a neuronal event somewhere in the nervous system’’ (p. 9). But my account will of course say that if the physiological account is satisfactory this neuronal event will be a realizer of pain, and that it causes what it does in virtue of the fact that it contains an instantiation of pain, i.e., in virtue of the fact that the causal profile of the property of which it is an instance contains as a part the causal profile of the property of pain, and the fact that it is this part that is activated. If Jaegwon has an objection to this, he doesn’t give it. Finally, let me address Jaegwon’s claim that the second-order view is favored, over the subset view, by the fact that second-order realization is an explanatory relation. It gives us an explanation that solves the explanatory gap problem by explaining why it is that, e.g., there is pain wherever there is C-fiber stimulation. I fail to see why the subset account doesn’t do this equally well. What his explanation is supposed to do is to show ‘‘how pains can be deduced from Cfs and other facts at the physical/neuronal level alone’’ (p. 11). His deduction goes by way of what he says is a definition, saying that to be in pain is to be in a state that plays a certain causal role. On his understanding of that definition the states that play that causal role have to be neuronal states like Cfs. But the proponent of the subset view can

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give same deduction, involving the same definition, but insist that pain itself counts as a state playing that causal role. Perhaps Jaegwon’s definition should be replaced in the deduction with two statements, one saying that pain is the property having a certain causal profile, and the other saying (what really should go without saying) that having a property whose causal profile includes that one is sufficient for being in pain. Before I leave Jaegwon’s comments let me say that I welcome his simplification of my subset account—i.e., his formulating it in terms of the forward-looking causal features of properties, or what he calls their powers, and dropping the reference to backward-looking causal features. This returns to the formulation I gave in an earlier paper, before I was misled into thinking that I needed to bring in backwardlooking causal features in order to deal with the alleged possibility that there can be properties that differ despite having the same forward-looking causal features. I am now convinced that that alleged possibility is not a real possibility, and that the forward-looking causal features determine the backward-looking ones, making it unnecessary to mention the latter in the account. I turn now to the comments by Louise and Andrew. Both of them are skeptical, to say the least, of my claims about the coincidence of persons with other entities, my distinction between thin properties and thick properties, and my notion of realization2, the relation that is supposed to enable properties of one thing to realize properties of a different thing that coincides with it. Louise, unlike Andrew, seems willing to allow that there may be room for employment of the realization2 relation in dealing with the relation between persons and their bodies. But she and Andrew both question my view that persons are coincident with animals who do not share their mental properties but have thin properties that realize2 these properties. Let me begin by saying something about the mentality of animals I don’t say in the book. I think that persons are animals in the same sense that dogs and chimpanzees are, and that animals in this sense have mental states and psychological persistence conditions. In the case of dogs or chimps, as in the case of persons, I think a brain transplant would involve a change of body—the dog or chimp would go with the brain, and acquire a new body. When I say in my book that persons are not identical with, but only coincident with, animals, I mean that they are not biological animals, in a technical sense of that term, where the persistence conditions of biological animals are biological, not psychological. Persons are not identical with biological animals in this sense, and neither are dogs and chimps—we are constituted by and coincident with biological animals, not identical with them. But in a good sense we are all animals, and in that sense animals can think and have mental states. My main reason for holding that persons are not identical with their bodies or with biological animals is hinted at in what I just said. My book is not about personal identity, and does not defend my views on that topic; but it alludes to, and assumes, the view I have defended at length elsewhere that hypothetical cases of change of body, beginning with Locke’s Prince-Cobbler case and running through cases of brain transplants and cerebrum transplants, support the view that the persistence conditions of persons are psychological. If one allows that in the brain transplant case the recipient is the same person as the donor, one is committed to the

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non-identity of persons with their bodies—and also their non-identity with the biologically individuated animals they coincide with. And if one is unwilling to hold that there are always three mental subjects, having the same mental states, where we would take there to be only one, one needs to hold that mental properties are thick properties that a person does not share with her concident body and biological animal. If one further thinks that the physical states of the body and the biological animal guarantee that certain mental states are instantiated, one needs the notion of realization2. Louise offers a way around this that I will discuss later. One of Andrew’s questions asks for cases other than those of persons and their bodies in which we have pairs of distinct but coincident objects and a need for the distinction between thick and thin properties. This is a fair request, and I can see why he is skeptical about whether it can be met. I think that the thick/thin distinction does have application elsewhere. I would count biological properties of trees as thick properties, and size and shape as thin properties of them. Likewise, the memory capacity of a computer would be a thick property of it, while its mass would be a thin property. But we do not have convenient names for entities that are coincident with trees or computers and share their thin properties but not their thick properties. We do not speak of these things as having bodies. This goes with the fact that we cannot envision scenarios involving such things that are analogous to the change of body scenarios we can envision in the case of persons. I think it also goes with the fact that dualist views that are prima facie plausible in the case of mental properties are not intelligible as views about biological properties or computer properties. To the best of my knowledge, no one has ever taken seriously the idea that there are disembodied trees or disembodied computers. For a variety of familiar reasons, mental properties are special, and it is not surprising that distinctions like that between subjects of mental properties and their bodies are marked in our language while analogous distinctions applicable to trees and computers are not. Still, while we don’t speak of trees as having bodies, we do speak that way of nonhuman animals. And in the case of trees we can speak, following Andrew, of the ‘‘swarm’’ of particles that constitutes it at a time—and this won’t be a tree, but will share the tree’s size, shape and mass. Underlying a lot of what I say about coincidence is the idea that there is an internal relation between the persistence conditions for things of a sort and the nature of the properties that things of that sort have, where the nature of the properties is given by their causal profiles. Central to causal profiles of some properties, especially those I count as ‘‘thick,’’ is the aptness of instances of them to cause, or contribute to causing, instances of what we can call ‘‘successor properties,’’ later states of the same thing. Thus being elastic involves being such that when subjected to certain forces it, that same thing, will change shape and then, when those forces are removed, will revert to its original shape. And of course various mental states are such as to lay down memories of themselves, where the memory and what it is a memory of belong to the same subject. The persistence conditions must be such that the possessor of the successor properties will count as the same thing as what had the properties of which they are successors. I think this should remove Louise’s worry that ‘‘the explanatory story is backward’’ in my account. The worry is that while the reasonable thing to say is that

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individuals are psychological beings, e.g., persons, in virtue of having psychological properties, on my account ‘‘it looks as if one has psychological properties in virtue of being a person.’’ Personhood, she says, turns out to be ‘‘a kind of surd.’’ My reply is that what we have here is a package deal. In virtue of the internal relation just mentioned, the account of what makes the psychological properties the properties they are and the account of what makes their subjects the kinds of things they are, of what gives them their persistence conditions, are two aspects of the same thing. Louise would avoid my view that we are non-identical with human animals, and do not share mental properties with them, by taking personhood to be a phase-sortal property of animals. This involves reinterpreting change of body arguments so that the conclusion is stated in terms of Parfitian survival rather than identity. So in her example Sara, whose cerebrum gets transplanted, survives as the person with her cerebrum and a different body, the person she calls ‘‘Sarabrum,’’ but is not identical with her. There is then no need on this account to distinguish Sara from the biological animal that constitutes her, and so need for the thick/thin distinction. This move is motivated by the view that my account makes personhood ‘‘a kind of surd,’’ and I hope that I have defused that with my point about the internal relation between the nature of mental properties and the nature and persistence conditions of their subjects. Since I think that her discomfort with realization2 and the thick/thin distinction is groundless, and since the identity interpretation of change of body cases seems to me much more natural than the interpretation in terms of Parfitian survival, I prefer the former. Where possible, what we count as survival should be construed as involving identity. Some philosophers, most notably David Lewis and John Perry, have even tried to construe the ‘‘survival’’ in fission cases as involving identity. I don’t think those attempts succeed; but there is no obstacle to construing the survival in transplant cases as involving identity. In addition, there is a kind of case that her proposal cannot handle at all. In the book I describe a case, call it the Jekyll/Hyde case, in which two persons coincide throughout their careers, each manifesting its mental states in the behavior of their shared body during periods in which the other sleeps. There are two different series of mental states realized in the states of the shared body; the members of each of them exhibit the psychological continuity and connectedness typical of a normal human life, but there is no relevant connectedness between the states in the one and the states in the other. Here there is a single human body, and a single biological animal, but there are two different persons. I see no way in which this can be described in terms of Parfitian survival rather than identity. I think that what I have said answers Andrew’s question about why we should believe in thickness. Two others of his questions concern what he calls ‘‘doubling.’’ I take it that doubling is what on my view we don’t have with thick properties because of their failure to be shared by coincident entities. One question is ‘‘How is the doubling of thin property instances to be avoided?’’ I am not sure what he means by this, given that thin properties are defined as ones that are shared by coincident entities. In any case, his next question is that if I find the doubling of thin properties acceptable, what do I find unacceptable about the doubling of instances of thick properties? He says that the idea that there are two objects weighing 200 lb on the

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scale loses its sting when it is pointed out that the two objects have the same parts, so ‘‘one wonders why the idea that my body and I are both in pain does not also lose its sting once it has been explained that my body and I also have exactly the same physical parts.’’ Part of the answer to this is that while the weight of a thing is a function of what its parts are and what they individually weigh, a thing’s being in pain is not determined by anything comparable with that. But we get a fuller answer if we address the question of why the microphysical state of affairs that realizes in me the property of being in pain doesn’t realize that property in my body—and in my biological animal. After all, this state of affairs occurs in the career of my body, and in the career of my biological animal, as well as in my career. One can answer this question with a distinction, not made in the book, between two ways in which a microphysical state of affairs can be said to be embedded in the career of a thing. In the first sense, call this weak embedding, the state of affairs’ being embedded in the career just consists in its occurring in it—it consists in certain of the thing’s component microentities being propertied and related in a certain way. In this sense a state of affairs that is embedded in a thing’s career will be embedded in the career of anything coincident with that thing. In the second sense, call this strong embedding, a state of affairs will be embedded in a thing’s career only if it realizes a property instance that is, in virtue of the nature of its causal profile, synchronically and diachronically unified with other property instances in that career. Suppose the state of affairs is a realizer of a thick property, like being in pain or thinking of Vienna. It will be a realizer of this property simpliciter; if it occurs then, necessarily, there is an instance of that property. But the only career in which it is strongly embedded is one in which the instance of the property stands in the appropriate relations of synchronic and diachronic unity to the other property instances; this will be the career of a mental subject, not the career of a body or the career of a biological animal—although the state of affairs will be weakly embedded in those. This can be illustrated with the Jekyll/Hyde case mentioned earlier. The career of the animal that coincides with both Jekyll and Hyde will contain all of the microphysical states of affairs that realize states of either of them—and these states of affairs will occur in, and so are weakly embedded in, both. But some of these states of affairs will realize mental states of Jekyll, while some will realize mental states of Hyde. The Jekyll states will exhibit the psychological continuity and connectedness that makes them the career of a single person, i.e., constitutes the persistence over time of a mental subject. And the same will be true of the Hyde states. So the Jekyll states will be strongly embedded in the Jekyll career and the Hyde states will be strongly embedded in the Hyde career. But the series that includes both the Jekyll states and the Hyde states will not exhibit this psychological continuity and connectedness, for Jekyll and Hyde states will not stand to one another in the right sorts of causal connections. I think that the distinction between weak and strong embedding can be used to clarify my notion of realization2, i.e. the sort of property realization in which a thin property instance realizes a thick property instance and these can occur in different but coincident things. The realization2 by a thin property instance occurring in one thing of a thick property instance occurring in another thing coincident with it is just

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a matter of these instances having as their microphysical realizer the same microphysical state of affairs which is weakly embedded in the career of the one and strongly embedded in the career of the other. I hope that I have already answered Andrew’s question of why we shouldn’t just identify persons with their bodies. But I should address some things he says in developing this question. He says that unless we identify the knife with the piece of steel we cannot explain why the knife conducts electricity. I have no problem answering that—being a conductor of electricity is a thin property, and shared by the knife and the piece of steel. But he goes on to suggest that on my account there is no satisfactory answer to the question of how a person has a certain weight, indeed why a person has any physical parts. Speaking of someone who weighs 120 lb, he asks ‘‘how does her swarm’s weight become her weight, given that she is distinct from the swarm?’’ To the reply that she weighs the sum of the weights of her physical parts he responds ‘‘this answer just assumes that the physical parts of her swarm are also physical parts of her, whereas it isn’t obvious that she has any physical parts, given that she is distinct from her swarm.’’ In response to all this, let me point out that in Chapter Five of my book there is an explicit account of what it is for a microentity to be a part of an object, one that applies to anything having the sorts of properties I am discussing and so one that applies to subjects of mental properties. I won’t try to give the whole account here; I will just observe that it makes use of the account of microphysical realization developed in Chapter Three, the idea that property instances are realized by microphysical states of affairs, and takes the microentities that are parts of a thing to be a special subset of the microentities involved in the states of affairs that realize the thing’s property instances. This should remove any worry that my account cannot allow for persons having physical parts. The last thing in Andrew’s comments I want to discuss is his question about modal properties. This arises because I appeal to modal properties in making the case for coincident entities. He worries that there is nothing physical that grounds the distinction between having a shape essentially, as a statue is supposed to do, and having it only contingently, that the distinction between essential and accidental properties may be grounded in mental phenomena, and that if it is ‘‘the essential rather than accidental possession of a property by an object is not an objective feature of the object.’’ In my view modality is built into the very nature of physical properties—such properties are individuated by causal profiles, and causal profiles are partly modal profiles. What probably underlies the idea that the essentiality of a statue’s shape is grounded in something mental is the fact that it seems to be a conceptual truth that statues have their shapes essentially, and the fact that our having a concept is something mental. But while our concepts determine what properties our terms or thoughts refer to, they are not what give those properties their modal profiles. That said, I should acknowledge that artifact properties, like being a statue, involve their concepts in ways other properties do not. The property of being an oak tree could be instantiated even if there were no concept of it, but, arguably, the property of being a statue depends for its existence on there being the concept of it, or at least of there being, or having been, mental states whose contents are about statues. The property

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of being a statue is not an intrinsic property; it is a property something has in virtue of existing in a social context in which certain purposes are served by the creation and preservation of statues. It is the nature of this social context, and the practices involving statues that constitute it, that gives statues their persistence conditions and gives the property of being a statue its causal and modal profile, thus making the shape of a statue essential to it. The existence of this social context is no doubt something psychological, but it is something perfectly objective, and something that is physically realizable. And the essentiality it gives to the shapes of statues is perfectly objective. I very much like what Louise says at the end of her comments about how the realization-independent detection of higher order properties, and mental properties in particular, fits in with the subset account. The forward-looking causal features of a mental property include its aptness to cause states that represent its instantiation— I assume she has in mind both states that occur in introspective detection and ones that occur when the detection is based on observed behavior. And the exercise of this aptness does not require representation of the instantiation of realizers of the mental state, and is compatible with the lack of the ability to detect and represent the realizers. This aptness is also a feature of the properties that are physical realizers of the mental property—but it is a feature they have only because they are realizers of the mental property. Here we have a good illustration of how it can be the case that a lower order property can cause something because its causal profile includes that of a higher order property it realizes. I was going to complain that what Louise says does not remove my puzzlement about how to draw the distinction between genuine and phony properties; but then I saw that she was not trying to do that, since she says that she cannot ‘‘give us a criterion for decisively throwing out any property as ‘phony’.’’ So I will leave it at that.

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