Source: http://theotodman.com/Abstracts/Abstract_12/Abstract_12013.htm
Timestamp: 2019-04-18 14:29:15+00:00

Document:
(OO-L): This chapter considers the view that we are literally brains. It argues that the view is best supported by the claim that brains are the primary subjects of mental properties, giving a “thinking-brain problem” analogous to the thinking-animal problem that supports animalism1. The brain view is shown to have implausible consequences about our identity through time, and to presuppose that something is a part of a thinking being if and only if it is directly involved in that being's mental processes. It is then argued that the notion of direct involvement is too interest-relative to give this principle any useful content, and that the principle is in any case unfounded.
If we are neither animals nor material things constituted by animals, we might be parts of animals. This chapter is devoted to the view that we are spatial parts of animals; the next asks whether we are temporal parts. The only spatial parts of animals that I can think of any reason to suppose we might be are brains, or something like brains – parts of brains or perhaps entire central nervous systems. Call the view that we are something like brains the brain view.
The brain view says that we are identical with brains, not that we “are” brains in some looser sense. It is not the view that our brains are important to our being in a way that none of our other parts are. Nor is it that our brains constitute us, or that we are temporal parts of brains (views I will briefly discuss in §4.3). The brain view is that we are literally brains. So it implies that you are about four inches tall and weigh less than three pounds. You are located entirely within your cranium and made up mostly of soft, yellowish-pink tissue. In normal circumstances we never strictly see ourselves or each other. This might sound like something out of a comic book. Some readers, I’m sure, are already thinking of jokes. Is it really a serious view?
One could defend the brain view by pointing out that even if you are a brain, it may still be true to say, in ordinary circumstances, that you are five or six feet tall, that you weigh more or less what the scales say when you step on them, and that you see yourself when you look in a mirror. These things might be true because your animal body has those properties. A brain can be six feet tall in the sense of having a six-foot-tall body. And that sense may be all we mean when we say, in ordinary contexts, that some of us are six feet tall. If so, the ordinary belief that some of us are six feet tall is perfectly compatible with the brain view. Those who believe that we are immaterial and have no physical properties at all have been saying this sort of thing for centuries: an immaterial thing can “be six feet tall” in the same sense as a brain can.
Whether linguistic hypotheses of this sort make the brain view any easier to believe is debatable. It may only combine an absurd view about what we are2 with an implausible view about what we mean. When we say that Haroun is six feet tall, we don’t seem to mean merely that he relates in a certain way to something or other that has the property of being six feet tall. We seem to mean that Haroun himself has that property. And there doesn’t seem to be any sense in which Haroun is four inches tall.
In any case, the brain view is the sort of thing that only a philosopher would think of, and only at the end of a long chain of argument. That may be why it is hard to find anyone who seriously advocates it3. But even if no one thinks that we are brains, the view raises important issues that bear on other accounts of what we are4. So we cannot avoid discussing it.
Why suppose that we are brains? Well, it would support the conviction that you could survive the loss of your fingers, legs, abdominal organs, and so on, but not the loss of your brain – that you could be pared down to a naked brain (or a part of a brain), but no further. (I don’t say that this conviction is true; but it is widely held.) Of course, you couldn’t survive for very long as a naked brain – at any rate not without life-support machinery far more advanced than anything now in existence. But it may seem that you couldn’t survive even for a moment without a brain. If you are your brain, the reason for this would be simple: destroying your brain would literally destroy you, whereas cutting away your limbs and other organs would only change your surroundings, albeit in a drastic way.
Likewise, the brain view fits nicely with the conviction that you would go along with your transplanted brain5. According to the brain view, to transplant your brain6 is literally to transplant7 you: to cut you out of your head, move you across the room, and then re-house you in a new head. If you were any material thing other than your brain (or a part of it), the view that transplanting your brain8 would transplant9 you would appear to have the awkward implication that the surgeons would move two brain-sized things across the room – you and your brain – raising the awkward question of what the relation would be, in mid-transplant10, between those two objects. (Friends of the constitution view11 have an answer to this question; but we have seen that it has its faults.) The brain view has the virtue of offering an entirely straightforward account of what happens in brain transplants12.
Better yet, it offers a solution to the thinking-animal problem (Persson 1999: 521). Anyone who believes that we are not animals needs to say something about those human animals13 that appear to think our thoughts. Why don’t they count as people? And what reason could we have to suppose that we are not those animals? Friends of the brain view can answer that in the strictest sense human animals14 don’t think our thoughts: they think only in the derivative sense of having brains that think. The existence of unthinking animals15, or of animals that think only in a loose sense, is no threat to the claim that you and I are not animals. To my mind, this line of thought offers the best argument for the brain view. More importantly, perhaps, it poses a problem for anyone who believes that we are not brains: what grounds could you have for supposing that you are something other than your thinking brain? Call it the thinking-brain problem.
The brain is our organ of thought. We think with our brains, and not with our lungs or kidneys or any other parts of our bodies. The brain produces thought, much as the liver produces bile. So it seems, anyway. This suggests that the brain thinks. Just as the heart’s function is to pump our blood, the brain’s function is to think. (As before, let us take “thought” and “thinking” as broadly as possible, to include not only active cogitation but mental activity and states generally.) Philosophers of mind often say that if any material thing thinks, it is the brain: they ask whether a material thing could be conscious by asking whether a brain could be conscious. They ask whether mental states are physical states by asking whether they are brain states. But what could a brain state be, if not a state of a brain? And if a mental state is a state of something, that something ought to be the subject of that state, or at any rate a subject of it – that is, a thinking or conscious being. What more could it take for a thing to be conscious than for it to be in conscious states?
But if the brain thinks, that suggests that anything larger than a brain – a human animal16, a thing constituted by a human animal17, or what have you – could be said to think only in the derivative sense of having a part that thinks. Brains, by contrast, would think in the strictest sense. They would have the property thinking; larger things could at best have the property having a thinking part. But having a thinking part doesn’t seem to be a way of thinking. The solar system, if there is such a thing, has many people as thinking parts. Yet clearly it doesn’t think. Not in any interesting sense, anyway. Maybe a human organism that thinks by virtue of having a thinking brain as a part bears a more intimate relation to the property of thinking than the solar system does by virtue of having a thinking person as a part, and this difference explains why we say that human organisms think and the solar system doesn’t. Even so, if it is the brain that thinks, it looks as if nothing larger than a brain could think in the strictest and most straightforward sense. Anything larger than a brain could think only a derivative sense – in the sense of having a special sort of part that thinks in the strictest sense. But isn’t it obvious that I think my thoughts in the strictest sense? Surely it couldn’t turn out that strictly speaking it is something other than me that thinks my thoughts, while I myself think only in some loose, second-rate sense. It follows that I could not be anything other than my brain. If the true thinkers of our thoughts – the beings that bear our mental properties in the most robust sense – are brains, then we must conclude, however reluctantly, that we are brains.
(1) There is such a thing as my brain.
(2) My brain thinks my thoughts in the strictest sense.
(3) If my brain thinks my thoughts in the strictest sense, then anything else that thinks my thoughts does so only in the derivative sense of having a part that thinks in the strictest sense.
(4) If anything thinks my thoughts in the strictest sense, I do.
It follows from these four premises that I am my brain. Those who think that we are not brains are committed to denying one of them. Let us consider the prospects for resisting the argument.
That is how it seems to me. But I needn’t insist on this point. Those who say that you and I – the beings we refer to with our personal pronouns – don’t think in the strictest sense disagree with me only about words. As I said in §1.4, if the beings that think our thoughts are different from the beings our personal pronouns and proper names denote, the important matter is the nature of the beings that think our thoughts.
What about the first premise, that there is such a thing as my brain? This might seem hard to deny, unless we are idealists and deny the existence of material things generally. But some philosophers concede that there are particles "arranged cerebrally" within my skull, yet deny that those particles compose anything. There is nothing, they say, that has all those particles as parts, and all the parts of which overlap one or more of those particles. We encountered this sort of sparse ontology of material objects in the previous chapter, and we will return to it in §§6.4 and 9.5.
The third premise was that if my brain thinks, then anything else that thinks my thoughts does so only in the derivative sense of having a part that thinks. Though this looks right to me, I wouldn’t defend it to the death. It is not generally true that whenever an object has a part that is F, that object itself is F only in the sense of having an F part. If my foot is injured, then I am injured, and not, it seems, merely in a loose and derivative sense. It seems that I am injured in the same sense as my foot is: I really do have the property being injured, and not merely the property having an injured part (though I have that property too). Thinking might be like that: perhaps both my brain and I think in the strictest possible sense. If so, then the fact that my brain thinks provides no reason to suppose that I am a brain rather than, say, an organism, and the argument for the brain view fails.
Even if this is right, though, it would offer little comfort to those who think that we are not brains. If I am something other than my brain, yet my brain thinks in the same strict sense as I do, then I am one of at least two beings thinking my thoughts. That makes it hard to see how I could have any reason to suppose that I am the non-brain that thinks my thoughts rather than the brain that thinks them. And we can hardly assert that we are not brains if we have no reason to suppose that this is the case. So even if the thinking-brain problem doesn’t show that we are brains, it may show that we have no reason to suppose that we’re not, and that would be trouble enough for anyone who rejects the brain view. We will return to this matter in §9.3.
Those who deny that we are brains are most likely to say that our brains don’t think at all, contrary to premise 2. We use our brains to think, they will say, just as we use our eyes to see, but our brains no more think than our eyes see. Our brains do something necessary but insufficient for us to think. We think not by having thinking brains, but by having brains that do something other than thinking. Our brains may have neural structures that in some sense underlie mental properties, but they themselves lack those mental properties. We might call what the brain does “subthinking”, as opposed to genuine thinking.
This attractive thought is surprisingly hard to defend. It is plain enough why our eyes don't see: the existence of open eyes in good working order in the presence of well-lit visible objects is not enough for seeing to take place. What the eyes do is only a small part of the activity of seeing. You need more than just eyes in order to see: you need something like a brain as well. But you don't seem to need anything more than a working brain in order to think. It is a philosophical commonplace that a brain removed from someone’s head and kept alive in a vat could think. (It may of course be false, but it is no less commonly held for all that.) Some doubt whether a brain that had always been in a vat could think, as it is unclear what could give its states any content – what could make them thoughts about Vienna, say, rather than about something else or about nothing at all – but this wouldn’t prevent a brain that was removed from someone’s head yesterday from thinking. And if a brain in a vat18 can think, why not a brain in a head?
Some say that thinking is a biological property that only an organism could have. This is the opposite of Shoemaker’s claim (§2.5) that it belongs to the nature of mental properties that biological organisms cannot have them. If this is right, then our brains cannot think because they are not organisms. Now maybe a detached brain, kept alive in a vat, would actually be a biological organism: maybe you could make a human organism smaller by removing all of it except its brain, much as you can make a human organism smaller by amputating a finger (van Inwagen 1990a: 172-181). That would make the suggestion that thinking can be a property only of organisms compatible with the claim that a brain in a vat19 could think. But the brain view is not that we are detached brains in vats20, but that we are undetached brains in heads, and they are not organisms.
If it were absolutely impossible for anything but a biological organism to think, it would be big news. It would rule out the possibility of artificial intelligence, or at any rate inorganic artificial intelligence. The only way to create artificial intelligence would be to create an artificial biological organism that was intelligent. Gods, angels, and immaterial thinking substances would be impossible. For that matter, the view that only organisms could think would rule out every account of what we are21 apart from animalism22 and the view that we don’t exist at all. That would make it a good deal easier to work out what we are!23 Until we see an impressive argument for this bold claim, we had best be on our guard.
Others say that it belongs to the very idea of thinking that no thinker can be a proper part of another thinker. Thinking, in other words, is maximal24. Given that I think, and that my brain is a part of me, it follows that my brain cannot think – though a naked brain that wasn’t a part of a larger thinker might be able to think. A thing that was otherwise ideally suited to be a thinker might be unable to think merely because it had the wrong neighbors. I don’t myself find this idea at all plausible. I find it hard to believe that an embodied brain should be prevented from thinking by its fleshy surroundings, and that it would blossom instantly into a thinker if only the flesh were removed. In any case, the maximality of thought would not explain why our brains cannot think. It implies that if a whole human being can think, then its brain cannot. But it also implies that if the brain can think, the human being cannot. And by itself it provides no support for one starting point over the other.
It may be that we don’t ordinarily call what brains do ‘thinking’. At any rate we commonly apply the word ‘thinking’ to things the size of human animals25 and we don’t (it seems) commonly apply it to brains. And someone might wonder whether it is really possible for us to be mistaken about this. Surely it couldn’t turn out that all the things we call ‘cats’ were really dogs and all the things we call ‘dogs’ were really cats. We can occasionally mistake a dog for a cat, but we couldn’t be thoroughly and systematically mistaken about which things are cats (assuming, at least, that there really are material things we call ‘cats’). If none of the furry domestic animals that purr and chase mice were cats, what would give the word ‘cat’ its meaning? This might suggest that we could not be thoroughly and systematically mistaken about which things are thinkers either. Don’t we mean by ‘thinking’ whatever it is that things the size of human animals26 do, and not whatever it is that brains do? What brains do may be very like thinking, but the way we speak shows that it does not fall within the extension of the word ‘thinking’ or the concept it expresses. Therefore, the argument would go, brains don’t think.
But the concept of thinking, or the meaning of the word ‘thinking’, does not appear to have built into it any restriction on the size or shape of the things it applies to. The hypothesis that brains think and things the size of human animals27 don’t think does not appear to conflict with the meaning of ‘thinking’ in the way that the hypothesis that all the things we call ‘cats’ are really dogs and all the things we call ‘dogs’ are really cats appears to conflict with the meaning of ‘cat’. Many people have believed that the thinkers of our thoughts are immaterial souls rather than things the size of human animals28. That view has its faults, but it doesn’t appear to be internally inconsistent on account of the meaning of the word ‘thinking’. It isn’t like saying that wholly unconscious beings might think. The same appears to go for the hypothesis that brains think. Nor can anyone argue that if things the size of human animals29 don’t think, we lose our grip on the meaning of the word ‘think’. We can say a good deal about what thinking involves – for instance that it has to do with inner representational states mediating between sensory stimulation and behavior – without saying anything about the intrinsic nature of the beings that engage in it. That, indeed, is the main insight of the functionalist theory of mind.
Someone may doubt whether there is any hard fact of the matter as to whether brains think and human animals30 (or things the size of animals) merely have thinking brains as parts, or whether animals think and brains merely have neural properties that underlie thinking. Brains, the idea goes, have a property that is a good candidate for being called ‘thinking’, and animals have another property that is an equally good candidate for being called ‘thinking’, and that’s all there is to it. To ask whether the brain property or the animal property is really thinking, or whether both are, is to ask an unanswerable question.
I don’t think this idea is forced on us, though it is certainly a possible view. It would imply that it is indeterminate which things think our thoughts: whether it is brains, or things the size of human animals31, or perhaps things of intermediate size – heads, say. Given that we think our thoughts, it would follow that it is indeterminate which things we are. It would not be definitely true that we are brains, but not definitely false either; and likewise it would be neither definitely true nor definitely false that we are animals, or things the size of animals. It would therefore be indeterminate how big I am: whether I am six feet tall or small enough to fit into a hatbox. And it would be indeterminate whether anyone has ever seen me. We might call this rather untidy account of what we are32 the indeterminate-size view.
The indeterminate-size view would appear to share most of the disadvantages of the brain view: troubles for the view that we are brains will tend equally to be troubles for the view that we are not definitely not brains. (We will come to these troubles presently.) So we gain little if we try to resist the claim that our brains think by arguing that it is indeterminate whether brains or whole organisms think.
These reasons for supposing that our brains cannot think, or that they cannot think in the way that we can, are disappointing33. And the other ways of solving the thinking-brain problem aren’t very nice either. This is bad news for those who suppose that we are not brains, and good news for those, if there are any, who suppose that we are. For all that, I believe we can resist the claim that the true thinkers are brains, and thus solve the thinking-brain problem. First, though, I will consider objections to the brain view itself.
What is the case against the brain view? We have already noted its implication that we are far smaller than we thought and that we never really see anyone. It also appears to have repugnant implications about our identity over time. For example, it would make it impossible for anyone to have different brains at different times: you cannot exchange your old brain for a new one if you are your brain. If Shoemaker’s brain-state transfer machine were to copy the contents of your brain onto another brain while erasing the contents of the original brain (§1.7), then according to the brain view you would remain the original brain. The new brain (or the person whose brain it is) would of course believe that it was you, but it would be mistaken.
The brain view would seem to make it impossible for us to become wholly inorganic. Many philosophers find it fairly obvious that if your parts were gradually replaced with inorganic prostheses that duplicated the function of the organic parts they replaced, so that the resulting being always continued to think as you did, you would gradually come to have more and more inorganic parts and fewer and fewer organic ones until you were entirely inorganic (Unger 1990: 122, Baker 2000: 109). But it seems unlikely that any brain could become entirely inorganic. An organ that is now made up of living cells – that very thing – could not come to be made up entirely of metal and silicon.
Our brains also appear to have different histories from our own. Physiologists tell us that our brains come into being early in our gestation, before arms and legs appear, and long before we are capable of having any mental properties. If they are right, then according to the brain view that is when we begin. That is, we begin well after conception, but long before we acquire any mental capacities.
Or consider Einstein’s brain. A well-documented urban legend has it that Einstein’s brain is kept in a jar in Kansas, in the possession of the pathologist who did the autopsy after his death. Suppose the legend is true. It says that Einstein’s brain is now in a jar in Kansas. And the phrase ‘Einstein’s brain’ as it occurs in the legend appears to refer to the thing that was once the brain in Einstein’s head. If so, and if Einstein is the thing that was once (as we say) the brain in Einstein’s head, it follows that the thing in the jar in Kansas is Einstein himself.
No one is going to be happy with all of this. The persistence of my brain does not appear to be either necessary or sufficient for me to persist. Now the derivation of these unwelcome consequences of the brain view relies on assumptions about what it takes for a brain to persist: that you cannot move a brain from one place to another merely by transmitting information, for instance, that a brain cannot become wholly inorganic, and that a brain may continue to exist after the death of the organism of which it was once a part. And although these assumptions look right to me, they are not beyond question.
Or maybe the thing in the jar in Kansas isn’t really Einstein’s brain. It was never in Einstein’s head. Strictly speaking it is merely a sort of fossil relic of the organ that filled the great man’s cranium: it is made of much of the same matter as that organ was when Einstein died, and has inherited many of its properties, much as a mineralized skeleton has many of the properties that a certain animal had when it died. It may be correct to describe this situation loosely by saying, as the legend does, that the thing is the jar “is Einstein’s brain”, just as the museum curator might call a fossil skeleton a tyrannosaurus. But for all that it may be no more strictly accurate to say that the thing in the jar was once in Einstein’s head than it would be to say that the skeleton in the museum was a fearsome predator 100 million years ago.
Someone might even propose that the brain-state transfer machine doesn’t merely copy the psychological information from one brain onto another brain, but somehow moves a brain from one brain to another. Perhaps, despite appearances, there are really three brains in the story: the brain that the machine moves across the room, the brain left behind after the machine has done its work, and the brain onto which the first brain’s mental contents get copied. We might call them the travelling brain, the donor brain, and the recipient brain, respectively. The transfer procedure would presumably bring the donor brain into being (otherwise there would have been two brains in the same place before the transfer, the travelling brain and the donor brain – leaving us wondering why the machine moved one of them but not the other). No brain would first have and later lack the donor’s mental states. And the recipient brain, onto which the travelling brain’s mental contents are copied, would presumably cease thereby to exist, else there would be two brains in the same place after the transfer, the travelling brain and the recipient brain.
Interesting though these suggestions are, I find them hard to believe. No sort of psychological continuity34 appears to be necessary and sufficient for a brain to persist, for the same reason as no sort of psychological continuity35 appears to be necessary and sufficient for an organism to persist (§2.7). If brains really did persist by virtue of psychological continuity36, however, it would be unsurprising if the same were true of human animals37, thus rebutting one of the main objections to animalism38.
A better response to these worries about identity over time (or at least to some of them) is to say that the relation between a person and her brain is something more subtle than numerical identity. Some say that each of us is not strictly a brain, but rather a functioning brain, or a brain insofar as it is in certain states – states of the sort that make someone capable of thought and consciousness39. Because we are functioning brains – brains in the right states – we could not come to be non-functioning brains, brains in the wrong states. So the brain in the jar in Kansas is not Einstein. It is Einstein’s brain, but not his functioning brain. And you and I were never rudimentary embryonic40 brains incapable of consciousness, even though our brains were. The suggestion has to be that a functioning brain is something numerically different from a brain, so that when a brain stops functioning in the relevant way it may persist in a nonfunctional state, but the functioning brain goes out of existence altogether. If your functioning brain were your brain, or if ‘functioning brain’ were simply what we call a brain when it is functioning, then the view that we are functioning brains would be no different from the view that we are brains, and would have the same consequences about our persistence.
But what sort of thing is a functioning brain? How do functioning brains relate to brains – plain, ordinary brains that may or may not be functioning? (What sort of thing is a sleeping41 dog, and how does it relate to an ordinary dog that may or may not be asleep42?) You might suggest that the functioning brain is something the brain constitutes, in the sense of §3.1, just when it functions in the appropriate way. Or perhaps a functioning brain is a temporal part of a brain: a part composed of those temporal parts of a brain that function appropriately. It is hard to see what else the claim that we are functioning brains could amount to, if it is to block the brain view’s unwelcome consequences about our identity over time. Someone who took this line might also say that in special circumstances one of us might be constituted by different brains at different times, or by a brain at one time and by an inorganic gadget at another time. Or the view might be that one of us could be composed of temporal parts of two different brains, or of earlier temporal parts of a brain and later temporal parts of something inorganic (see §5.7).
But the view that we are things constituted by brains, or temporal parts of brains, is not the view that we are brains. It is not the brain view – though of course it resembles the brain view in obvious ways. These views may have an advantage over the brain view in that they agree better than the brain view does with what most of us are inclined to believe about our identity over time. But they also inherit the disadvantages of constitutionalism or the ontology of temporal parts. Moreover, they appear to face the same thinking-brain problem that arises for any other view according to which we are not brains: they make it hard to see how we can know that we are not the brains thinking our thoughts. They have no clear advantage over the view that we are constituted by or are temporal parts of whole organisms.
Those who say that we are brains will have to say some surprising things about our identity over time – though perhaps no more more surprising than what they have to say about our size.
To my mind, the most serious problem for the brain view has nothing to do with its implications about our size or our identity over time. The real trouble is that it is unprincipled and that there is no good reason to believe it.
If we are brains, it can only be because the brain is our organ of thought, and therefore the thing – the only thing – that thinks our thoughts in the strictest sense. (We could hardly be unthinking brains.) The reason why no one ever supposed that we might be livers or stomachs is that no one ever took the liver or the stomach to be our organ of thought. But what makes the brain our organ of thought? That is, why should the things that think our thoughts in the strictest sense be brains, and not, say, entire organisms?
Presumably the reason is that the parts of a thinker must all be in some sense directly involved in its thinking. Things larger than brains cannot think, except in the derivative sense of having a thinking part, because they have parts not directly involved in thinking. Yet not just any object, all the parts of which are directly involved in a being’s thinking, is a genuine thinker. No individual brain cell thinks, even if all its parts are directly involved in thinking. That’s because it doesn’t produce thought on its own: for any cell that is directly involved in my mental activity, many other cells are involved in it in an equally direct way.
If x thinks in the strictest sense at a time t, then y is a part, at t, of x if and only if y is directly involved in x’s thinking at t.
Call this thinking-subject minimalism. It is hard to see how the brain view could be true unless something like this is right. Otherwise it would be completely arbitrary to say that we are brains.
Thinking-subject minimalism is not very plausible. We seem to have parts not directly involved in our thinking: fingers, for instance. Suppose a certain part of your brain became inactive, so that it was no longer directly involved in your mental goings-on. Minimalism implies that this would make you a bit smaller and lighter – but losing a finger wouldn’t.
Still, it might have theoretical virtues. Consider the fact that there appear to be many candidates, of varying sizes, for being me: beings that seem to have all the equipment they need to think, and within which my mental activity takes place. There is my brain, and various parts of my brain, such as my cerebral hemispheres. There are also many candidates larger than my brain: my head, my upper half, this entire human organism, and so on. For that matter, we might ask why I am not something bigger still, which has this organism as a proper part. If there really are all these beings, what could prevent them all from thinking my thoughts? And if they do all think my thoughts, how could I ever know which one I am? How could I ever know how big I am – whether I am the size of half a brain or the size of a planet? Thinking subject minimalism might seem to solve this problem, by ruling out most of the candidates for being me on the grounds that they are either too big or too small to be genuine subjects of my thinking: too big because they have parts not directly involved in my thinking, or too small because not all the things directly involved in my thinking are parts of them. Then I could work out what I am43 by discovering which things are directly involved in my mental states and activities44.
So minimalism might tell us which of the many things that look like thinkers of our thoughts really do think them, thereby telling us which things we are. It would also appear to tell us what determines our boundaries, and what makes things parts of us – something we wanted an account of what we are45 to provide. Animalism46 tells us that we extend as far as our biological lives extend, because that is what determines the boundaries of a living organism (§2.2). Minimalism seems to tell us that we extend as far as our mental states and processes extend, because that is what determines the boundaries of a thinking being. Not every view about what we are47 tells us what fixes our boundaries: we noted in §3.6 that the constitution view48 doesn’t.
I have serious doubts about this story, however. Thinking-subject minimalism does not in fact tell us what beings think our thoughts. Nor does it tell us how big we are, or what determines our boundaries – even supposing that we know which particles are directly involved in which thoughts. Suppose for the sake of argument that all and only the parts of my brain are directly involved in my mental states and activities. Or rather, to avoid assuming the point at issue, suppose that all and only the parts of my brain are directly involved in those mental states and activities I think of as mine, or those that any part of this organism is directly involved in. Suppose further that every mental state must have a subject. Would minimalism imply, in that case, that my brain (or at any rate something the size of my brain) is the subject of my thoughts, and therefore what I am49?
No. Minimalism would not even imply that any thinking being is the size of my brain, let alone that I am. Suppose that one part of my brain is directly involved in some of those mental states and activities I think of as mine while another part, perhaps overlapping the first, is directly involved in the rest of them. Call them part one and part two, and call the mental states and activities they are directly involved in the part-one thoughts and the part-two thoughts, respectively. And suppose that every part of my brain overlaps part one or part two. (This story is not meant to be fanciful: it doesn’t require me to suffer from any sort of mental disunity.) Now it may be that both part one and part two are parts of me, in which case both the part-one thoughts and the part-two thoughts will be my thoughts, just as we should expect. But minimalism is also consistent with the view that the part-one thoughts belong to part one, the part-two thoughts belong to part two, and no being is the subject of both the part-one and the part-two thoughts. For all minimalism says, there may be just one thinker here – my entire brain – or there may be two – part one and part two. Nor does it rule out the possibility that the thoughts I think of as mine are divided among more than two thinkers. Minimalism will tell us the boundaries of a thinker only if we already know which thoughts belong to that thinker (as well as which particles are directly involved in those thoughts). But it doesn’t tell us which thinkers there are or what thoughts belong to a given thinker. And so it doesn’t tell us what our boundaries are. It doesn’t tell me whether I am my brain, or part one, or part two, or something else.
Now we could rectify this by combining thinking-subject minimalism with a principle that assigns thoughts to thinkers: a principle that would tell us, for instance, whether the part-one thoughts and the part-two thoughts all belong to the same thinker or whether the part-one thoughts belong to one thinker and the part-two thoughts belong to another. That is, we need an account of when mental states or properties belong to the same thinker and when they belong to different ones.
The only such account that I know of is the psychological individuation50 principle of §2.9. This was the idea that mental states belong to the same thinker if and only if they are causally unified in the right way: if and only if they are disposed to interact with one another, and with no other mental states, in the way that is characteristic of mental states. Your desires tend to interact with your beliefs to produce action: roughly, your desire for something tends to cause you to act in ways that you believe will satisfy that desire, unless you have stronger competing desires. Your desires don’t interact in that way with my beliefs. With any luck it will turn out that all and only the mental states realized in your brain are unified in this way. The psychological individuation51 principle will then imply that the mental states realized there, but no proper subset of them, are the thoughts of a single thinker; and that thinker will of course be you (who else?). It will rule out the possibility that some of the mental states realized in your brain might belong to one thinker while others belong to another thinker. Putting this together with thinking-subject minimalism and our assumption that all and only parts of your brain are directly involved in the mental states realized in your animal body, we get the conclusion that you are your brain (or at any rate something the size of your brain). We will see in §6.4, however, that the psychological individuation52 principle fits badly with the brain view: it seems to imply that we are bundles of mental states, and not material things at all.
Whether or not thinking-subject minimalism can tell us where our boundaries lie, there are grounds for suspicion about the principle itself. One worry is whether the principle has any real content. The very idea of “direct involvement in a being’s thinking” is suspiciously elusive.
One way to see this is to try applying the principle. What should we expect the true thinkers of our thoughts to be, according to minimalism? What thing is it that is composed of all the things directly involved in my thinking? (Let us assume that all the mental states I think of as mine really are mine, and are not divided among several thinkers.) The brain view takes for granted that it is nothing larger than my brain: nothing outside my brain is directly involved in my thinking. This is questionable (Schechtman 1997). Take visual experience: aren’t your eyes directly involved in your visual experience? You can’t have visual experience without eyes, or at least something like eyes. But if your eyes are directly involved in your visual experience, then according to minimalism they are parts of you and you are larger than your brain.
Even if nothing outside the brain is directly involved in my thinking, I am unlikely to be my brain. According to thinking-subject minimalism, brains will be too big to be genuine thinkers for the same reason as whole organisms are too big. The thing anatomy books call “the brain” has many parts that appear to be no more directly involved in producing thought than the heart is. Blood vessels, for instance: if the thing that pumps the blood to the brain isn’t directly involved in thinking, how can the vessels that distribute the blood within the brain be any different? Minimalism appears to provide no reason at all to suppose that we are brains. If we are anything smaller than whole organisms, we must be parts of brains.
But which parts? What parts of my brain are directly involved in my thinking? Its nerve cells, surely? Yet even that looks doubtful. No one knows exactly how nerve cells produce thought and experience, but it appears to have something to do with electrical and chemical signals that they store and communicate to other nerve cells. And a good deal of what goes on within a nerve cell appears to be no more directly involved in this storage and transmission of information than the activities of the heart and other vital organs are. Many parts of a nerve cell are involved in acquiring nutrients or in expelling waste, or in maintenance and repair, or in maintaining the cell’s boundary. They don’t seem to be directly involved in whatever it is that gives rise to thought. Minimalism seems to imply that not even the whole of any nerve cell could be a part of a thinker.
This ought to make minimalists uneasy. If neither the whole of the brain nor even the whole of any nerve cell within the brain is directly involved in thinking, what is directly involved? This unease can only grow if we think about how to distinguish in a principled way between direct involvement in a being’s thinking and indirect involvement. The point has nothing to do with thinking in particular. Imagine a factory that makes knives – an old-fashioned factory where the work is done mainly by hand, with no robots. All the factory workers are involved in some way in the manufacture of knives. Some deliver the steel; others beat it with hammers, sharpen the blades, stoke the fires, repair the tools, sweep the floors, run the canteen, keep the accounts; and so on. Which workers are directly involved in making knives, and which only indirectly? I don’t think we can say. There may be some sense in the idea that those who actually work the steel are more directly involved in the making of knives than those who sweep the floors. But is there really an absolute distinction – even an imprecise one – between those who are directly involved in making knives and those who are only indirectly involved? We could of course draw such a distinction for legal purposes – in order to work out insurance costs, say. But wouldn’t any such distinction be artificial?
Or think of walking. Which parts of a human being – which atoms – are directly involved in his walking? Those in his legs, surely. But are all the atoms in his legs directly involved in his walking? Suppose he has excess water in his legs owing to poor circulation, which hinders his walking. Are the atoms making up the excess water directly involved in his walking? (And what could determine which molecules are “excess”, and which belong there?) What about his arms, or spinal cord, or heart? Is their involvement in his walking direct or indirect? Again, although we may, perhaps, be able to say which parts of a human being are more directly involved in his walking than others, there seems to be no principled way of saying which are directly involved and which are not. This is not due to ignorance of the mechanics of walking: we should be just as baffled if we knew all that. Nor is the problem that the boundary between the parts of a human being that are directly involved in his walking and those only indirectly involved or not involved at all is indefinite, so that there are borderline cases that we cannot confidently classify either as “directly involved” or as “not directly involved”. Asking which parts are directly involved and which aren’t is like asking which rivers are long and which are not long. I see no reason to suppose that direct involvement in a being’s thinking is any different from direct involvement in someone’s walking or from direct involvement in making knives. Any decision about which are directly involved in its thinking is bound to be arbitrary.
I don’t mean to say that there is no truth at all in the claim that the brain, and not the liver or the stomach, is the organ of thought. Many parts of the brain are probably more directly involved in thinking than any other parts of the organism, just as those who beat the metal are more directly involved in making knives than those who sweep the factory floor. And anatomists distinguish an organ called the brain from the rest of the organism because what they call the brain contrasts noticeably with its surroundings (though its boundaries are not so neat as the anatomy books suggest). That is why we call the brain the organ of thought. But this is only a loose description. A great deal goes on within the brain besides thinking, and a great deal that goes on outside the brain contributes vitally to thinking. To say that the brain, or some part of the brain, is what does our thinking is no more strictly accurate than saying that the people who beat the metal are the ones who make the knives.
If this is right, thinking-subject minimalism has very little meaning. Saying that all the parts of a genuine thinker must be directly involved in its thinking is like saying that all the parts of a genuine walker must be directly involved in its walking. Because there is no saying, even roughly, which things are directly involved in thinking, there is no saying even roughly which things, according to minimalism, are the parts of a thinker. Or if there is a non-arbitrary way of saying which things are involved in a human being’s thinking, it is likely to be that they are all and only the parts of the organism. The organism has a non-arbitrary boundary, and it would appear to be the largest thing whose behavior we can explain in terms of its thinking. Though there may be a real sense in which thinking is something an organism does, there seems to be no real sense in which thinking is something a brain does53.
The text differs slightly from the book.
For “cut and paste” overflow reasons, the text is split between Abstract and Comment.
The view that we are brains is based on the idea that the parts of a genuine thinker are just those that are directly involved in its mental activity: thinking-subject minimalism. I have argued that there is no principled way of saying, even approximately, which things are directly involved in a being’s thinking and which are not. This leaves minimalism with no content, and the brain view without support.
I have another worry about minimalism. It arises even if we can say which things are directly involved in mental activity and which are not. Imagine that we know what direct involvement in mental activity is. Now: why suppose that the parts of a thinking being must be just those things that are directly involved in its mental activity? Why can’t a thinker – something that thinks in the strictest sense – have parts that aren’t directly involved in its thinking? In other words, why accept thinking-subject minimalism?
If x engages (in the strictest sense) in states or activities of kind K at time t, then y is a part, at t, of x if and only if y is directly involved in x’s K states or activities at t.
We might call this general activity minimalism.
If x engages in mental activity of any specific kind at t, then y is a part, at t, of x if and only if y is directly involved in x’s mental activity of that kind at t.
General activity minimalism cannot entail both thinking-subject minimalism and specific thinking-subject minimalism, for they are inconsistent (unless general activity minimalism is itself inconsistent, anyway).
If all of this makes sense, it is probably a safe bet that your vision module is not the same as your philosophy module. They may overlap, but they won’t coincide exactly. It follows that no genuine philosopher – no being that does philosophy in the strictest sense – is a genuine “seer”. One being now sees the book before you. Another being understands it. The one that sees the book does not understand a word of it, and the one that understands it sees nothing. Nothing both sees and does philosophy – not in the strictest sense, anyway. All true philosophers are blind. Reading, which involves both seeing and understanding, is an activity that nothing does, except in the derivative sense of having one part that sees and another part that understands. It is always a cooperative activity, like playing a duet.
More generally, given what we know about the division of labor in the brain, specific minimalism would make it unlikely that any being ever engages in more than one type of psychological task. Some see, some hear, some remember, some reason; but nothing does all these things, or even any two of them. For that matter, no one being is likely to engage in both short-term and long-term memory, or to reason about both geography and history. What we take to be a single person with general mental abilities is in reality a vast colony of numerically different specialists, each of which performs only a single sort of mental task. Call this view homunculism.
It is hard to see how homunculism could be true. Suppose I run a finger over the arm of my chair. I feel its rough texture and hear the scratchy sound it makes. In order to do this, I must both feel and hear. But homunculism implies that nothing both feels and hears. I should have thought it was utterly obvious that I do both feel and hear. For that matter, homunculism implies that nothing both hears and is reflectively aware that it hears: is unlikely, anyway, that the atoms directly involved in hearing are all and only the directly involved in being aware that one is hearing. Homunculism looks incompatible with the most basic sort of self-knowledge (Chisholm 1981: 87-88).
You might suggest that the being that thinks, “I both feel and hear”, needn’t itself feel or hear, but could be aware of another being’s feeling and a third being’s hearing as if they were his own. Then it might appear to me that I feel and hear even if I neither feel nor hear in reality. This would mean that a sensation or other mental state might appear to me for all the world to be mine even though it wasn’t. I could be aware of a searing pain down my left side that seemed to me just as if it were my own pain, even though in fact it was not mine but somone else’s. I might be aware of both a searing pain down my left side and a searing pain down my right side. The pains might be indistinguishable to me. For all I could ever know “from the inside”, the pain in my left side might be mine while the pain in my right side was someone else’s; or it could be the other way round; or it could be that neither was mine. I could never know, by introspection, which mental states were mine and which belonged to other beings. That, surely, is absurd.
Or consider what sort of beings you and I might be if homunculism were true. There would be many candidates, so to speak, for being me. There would be the being that does my philosophical thinking, or at any rate the philosophical thinking I take to be mine. (Or maybe different beings would do different kinds of philosophical thinking.) There would be the being that composes my written sentences, and the being that tastes my food. For every sort of mental activity that I in some sense engage in, there would be a different being – the genuine subject of that activity – that is a candidate for being me. But what thing should I be?
I might be one of the candidates. Which one? Perhaps the one asking the question: if I know anything, do I not know that I am now wondering what I am54? It would follow, given homunculism, that I am not the author of this book, for the atoms now directly involved in my wondering what I am55 are unlikely to be precisely the atoms directly involved in my writing. Now according to homunculism this book is unlikely to have any one author; it is almost certainly a collaborative effort. But if I am now wondering what I am56, then I am probably not any of this book’s authors. It is doubtful even whether I wrote this book in the sense of having one of its authors as a part: who’s to say whether any of the authors within my brain is a part of the being now wondering what I am57? More generally, few of the mental states I think of as mine would really be mine. Most of them would belong to beings that are not even parts of me.
Or perhaps I am not definitely any of the candidates; rather, when I say ‘I’ or ‘Olson’ I refer ambiguously to each of them. In that case it is presumably neither definitely true nor definitely false that I am the author (or an author) of this book, for although some of the referents of my ‘I’ were involved in writing it, many more were not. Nor will it ever be definitely true that I am feeling hungry, or thinking about Vienna, or in any other mental state.
Or I might be the thing composed of all the candidates. In that case it might be definitely true that I wrote this book, at least in the sense that all its authors are parts of me. But it would follow from this that I am probably not the true subject of any of my mental states or activities: I should reason, perceive, and remember only in the sense of having a part that reasons, a part that perceives, and a part that remembers. This would deprive the brain view of any attraction it may have had. There is no point in supposing that we are brains that think only in the sense of having thinking parts. If we have to accept that we think only in a derivative sense, we may as well say that we are whole organisms.
Homunculism is a hard view to like. Suppose it is false. Where does that leave the brain view? Well, the brain view assumes that whatever engages in mental activity generally is composed of just those things that are directly involved in its mental activity. But again, why suppose that? Why not suppose instead that whatever engages in some specific sort of mental activity, such as seeing, is composed of just those things directly involved in that specific activity? That leads to homunculism. Does anything support the brain view that does not equally support homunculism? (The other arguments for the brain view that we considered in §4.1 would support homunculism as much as they support the brain view.) In other words, is there any reason to suppose that thinking-subject minimalism is true rather than specific thinking-subject minimalism?
Call an activity such that whatever engages in it in the strictest sense must be composed of just those things directly involved in its engaging in that activity a minimalistic activity. Thinking-subject minimalism says that thinking or mentality in general is minimalistic. Specific minimalism says that specific types of thinking, such as remembering, are minimalistic. (Given how the brain works, thinking in general and remembering will not both be minimalistic.) Which is it? Is thinking in general minimalistic, or are specific types of thinking minimalistic? Or neither? What determines which activities are minimalistic and which are not? I have never seen an answer to these questions. Without such an answer, though, it is hard to see how anyone could be warranted in taking thinking in general to be minimalistic. And because the brain view depends on that claim, it too is unwarranted.
Someone might use the psychological individuation58 principle (§2.9) to argue that thinking in general is minimalistic while specific types of thinking are not. The principle says that particular mental states belong to the same subject if and only if they are causally unified with each other, and with no other states, in a certain way. Your seeing and your philosophizing are clearly unified in that way; so according to the principle they must belong to the same thinker. But there couldn’t be a being that was the subject of your seeing alone – a being that none of the other mental states we attribute to you belonged to – for although its mental states would be unified with each other in the right way, they would be unified in that way with many other states as well. That would be an argument against specific thinking-subject minimalism and homunculism, but not against general thinking-subject minimalism and the brain view. Howoever, for reasons we will come to in §6.4, the psychological individuation59 principle appears to be incompatible with our being brains.
To sum up: The main reason to suppose that we are brains is the idea that our brains are the true thinkers of our thoughts. That in turn is based on the claim that every part of a genuine thinker must be somehow directly involved in its thinking. But there appears to be no such thing as direct involvement in a being’s thinking. And even if there is, there is no evident reason to stop at thinking: why suppose that every part of a genuine thinker must be directly involved in its thinking, rather than that every part of a genuine seer must be directly involved in its seeing? Whatever supports the brain view appears equally to support the absurd idea that genuine thinkers are specialists capable of performing only a single mental task. So the brain is unprincipled as well as implausible.
Footnote 3: Puccetti (1973) takes each of us to be a cerebral hemisphere, and Hudson (2001: 143) says we are temporal parts of brains. Tye (2003: 142) says that we are brains, but appears to take it back on the next page. (His view may be that we are material things constituted by brains.) Though the view that we are brains is often attributed to Nagel, this does not appear to be his considered view (see Nagel 1986: 40). As far as I can see he has no account of what we are.
Footnote 24: Burke 2003: 112-113. More precisely, Burke’s view is that if x thinks, then no proper part of x whose particles would come to compose x if the rest of x’s particles were annihilated can think. The complication is designed to make the maximality of thought compatible with the possibility of a thinker’s being composed of many smaller thinkers in the way that a human organism is composed of cells. I will ignore it in the sequel.
Footnote 33: Burke 2003 gives further reasons, which I find equally unpersuasive. Logical behaviorists might argue that brains don’t think because they have no observable behavior; but I doubt whether there are any logical behaviorists nowadays.
Footnote 39: Tye says that we are “brains insofar as those brains are in the appropriate physical states (states sufficient for psychological states making up a single psychological framework)” (2003: 143). McMahan (2002: 88, 92) makes similar remarks – though he suggests a few pages later (94) that we have mental states as parts. In the same way, someone might try to avoid animalism’s consequences about our identity over time by saying that we are functioning animals rather than animals.
Footnote 44: Hudson makes this claim (2001: ch. 4). Because he believes that brains have temporal parts, some of which are not directly involved in producing thought, he takes thinking-subject minimalism to imply that we are certain temporal parts of brains rather than “whole” brains. We will return to the problem of how I can know how big I am in §9.3.
Footnote 53: TT Note: The book has a long footnote here.

References: §4
 §1
 §9
 §3
 §5
 §3
 §2
 §6
 §4
 §6
 §9