Source: http://theotodman.com/Abstracts/Abstract_12/Abstract_12011.htm
Timestamp: 2019-04-20 18:15:41+00:00

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(OO-L): This chapter examines animalism1, the view that we are biological organisms. It is based on the claim that human organisms think just as we do. This implies that if I am not an organism, I am one of at least two thinkers of my thoughts, making it hard to see how I could know that I am the non-animal thinker: the thinking-animal problem. Some proposed solutions are critically examined, notably Shoemaker's claim that human organisms cannot think and Noonan's account of how we might know that we are not the animals thinking our thoughts. Familiar objections to animalism2 are then reviewed, such as its implication that personal identity does not consist in psychological continuity3. It is argued that these objections are weak and that more serious worries lie elsewhere.
What sort of things might we be? Let us begin our study of answers to this question with the view that we are animals: biological organisms, members of the primate species Homo sapiens. This has a certain immediate attraction. We seem to be animals. When you eat or sleep9 or talk, a human animal10 eats, sleeps, or talks. When you look in a mirror, an animal looks back at you. Most ordinary people suppose that we are animals. At any rate if you ask them what we are11, and make the question clear enough to indicate that “animals” is one of the possible answers, they typically say that it is obviously the right answer. Few people would deny that we are animals. No one is going to feel immediately drawn to any of the alternative views – that we are bundles of perceptions, or immaterial substances, or non-animals made of the same matter as animals, say. Compared with those proposals, the idea that we are animals looks like plain common sense.
But things are not so simple. As we saw earlier, the appearance that we are animals may owe merely to our relating in some intimate way to animals – to our having animal bodies, if you like – rather than to our actually being those animals. The weight of authority is overwhelmingly opposed to our being animals. Almost every major figure in the history of Western philosophy denied it, from Plato and Augustine to Descartes, Leibniz, Locke, Berkeley, Hume, and Kant. (Aristotle and his followers are an important exception.) The view is no more popular in non-Western philosophy, and most philosophers writing about personal identity today either deny outright that we are animals or say things that are incompatible with it. We will come to the reasons for this unpopularity later.
The view that we are animals has become known as animalism12. Because animalism13 is easily confused with similar-sounding claims, I will say something about how I understand it. Animalism14 says that each of us is numerically identical with an animal: there is a certain organism, and you and it are one and the same. This would not bear stating but for the fact that some philosophers who deny that we are identical with any animal nonetheless insist on saying that we are animals. What they mean is that we “are” animals in some loose sense: in the sense of having bodies that are animals, or of being “constituted by” animals, or the like. We are animals in something like the sense in which an actor playing Lear is a king. That is not animalism15.
This terminological point calls for a brief comment. I wish I could persuade philosophers not to state views according to which we are non-animals by saying that we are animals. It forces us to express the view that we are really animals – that we are animals in the ordinary, straightforward sense in which we are people – with the ugly phrase ‘we are numerically identical with animals’. This is linguistically perverse: the most obvious interpretation of the sentence ‘That is an animal’ is surely that the denoted object really is an animal, and not that it relates in some way to something else that really is an animal. It is also tendentious: it makes animalism16 sound complicated and difficult when it ought to be simple and intuitive. Likewise, stating the view that we are non-animals constituted by animals (for instance) by saying ‘we are animals’ makes it sound simple and intuitive when it ought to be complicated and difficult. I, for one, refuse to play this mug’s game. When I discuss the view that we really are animals, I will state it by saying ‘we are animals’. And I will state the view that we are non-animals constituted by animals by saying ‘we are non-animals constituted by animals’. I encourage others to do the same.
Anyway, animalism17 says that we are animals, not that people in general are; so it is compatible with the existence of people who are not animals (gods or angels, say), and of animals – even human animals18 that are not people. Animalism19 is not an account of what it is to be a person, and implies no answer to the personhood question of §1.6.
The view that we are animals may call to mind the idea that we are identical with our bodies. What does animalism20 say about this? Is it the same as the view that we are our bodies? Does it at least entail that we are? I find these questions hard to answer. Suppose that a person's body, or at least a human person's body, must always be a sort of animal: none of us could possibly have a non-animal body. And suppose also that none of us could ever be an animal other than the animal that is his body. If these assumptions are true, then our being animals amounts to our being identical with our bodies. But are they true?
3 when our bodies are wholly organic, the two conditions coincide.
What it is right to say here depends on whether having some of your parts replaced by inorganic bits could give you a partly inorganic body (one that was not an animal), or whether it would only cause your body to shrink and become attached to those inorganic bits (as the animal would). And that depends in turn on what thing someone's body is. It depends, in other words, on what it is for a thing to be someone's body. For any objects x and y, what is necessary and sufficient for x to be y's body? What does it mean to say that a certain thing is your body, or that your body is an animal, or that someone might have a robotic body? Unless we have some idea of how to answer these questions, we shall have no way of saying whether someone might be identical with his body without being an animal or vice versa.
I have never seen a good account of what makes something someone's body (see van Inwagen 1980, Olson 1997: 144-150, 2006a). I don’t know how to complete the formula ‘necessarily, x is y’s body if and only if…’. Because of this I have no idea what would happen to someone’s body if some of a human animal’s21 parts were replaced with organic prostheses; and I therefore have no idea whether someone could be his body without being an animal or vice versa. So I cannot say how animalism22 relates to the thesis that we are our bodies. More generally, I find the word ‘body’ unhelpful and frequently misleading in metaphysical discussions. (§2.5 below gives an example of the sort of confusion it can cause.) For the sake of convenience I will sometimes use the term 'x's body' to mean the human animal23 intimately connected with x: the animal we point to when we point to x, the animal that moves when x moves, the animal that x would be if x were an animal at all, and so on. This is merely a stipulation, however, and does not pretend to reflect the way other philosophers use the word 'body’.
Here is another delicate matter. Suppose someone said, "We are animals, but not just animals. We are more than mere biological organisms." Is that compatible with animalism24? Does animalism25 say that we are nothing more than animals? That we are mere animals?
The answer depends on whether being "not just" or "something more than" an animal is compatible with being an animal. And that in turn depends on the import of the qualifications 'not just' and 'more than'. If a journalist complains that the Cabinet is more than just the Prime Minister, she means that the Cabinet is not the Prime Minister: it has other members too. If we are more than just animals in something like that sense, then we are not animals at all; at best we may bear some intimate relation to those animals we call our bodies. That may be because we have parts that are not parts of any animal, such as immaterial souls. On the other hand, we say that Descartes was more than just a philosopher: he was also a mathematician, a Frenchman, a Roman Catholic, and much more. That is of course compatible with his being a philosopher. We could certainly be more than just animals in this sense, yet still be animals. We could be animals, but also mathematicians or Frenchmen or Roman Catholics. There is nothing "reductionistic", in the pejorative sense of the term, about animalism26. An animal can have properties other than being an animal, and which do not follow from its being an animal. At any rate there is no evident reason why not. Despite its ugly name, animalism27 does not by itself imply that our behavior is determined by a fixed, "animal" nature, or that we have only crudely biological properties, or that we are no different in any important way from other animals. We could be unique among animals, and yet be animals.
Finally, animalism28 does not say that we are animals essentially; for all it says, our being animals might be only a contingent or perhaps even a temporary feature of us, like our being philosophers. Whether we could be animals contingently depends on whether human animals29 are animals contingently: whether it is possible for something that is in fact a human animal30 to exist without being an animal. Animalism31 implies that we have the metaphysical nature of human animals32; but what that nature amounts to is a further question (see below). My own view, and that of most philosophers, animalists33 or not, is that animals are animals essentially; but few arguments for or against our being animals turn on this claim.
2.2 What is an Animal?
Saying that we are animals will tell us little about what we are34 unless we have some idea of what sort of thing an animal is. I mean by 'animal' what biologists mean by it: animals are biological organisms, along with plants, bacteria, protists, and fungi. Animals are what zoologists study. Someone might say that ‘animal’ in the ordinary sense of the word means nothing more than ‘animate being’ – a thing that can move and perceive – and that whether animals in this sense are biological organisms is an open question. If that is the case, then my use of the word ‘animal’ is not the ordinary one, and I ought to have used the term ‘organism’ or ‘animal in the biological sense’ instead.
As I see it, animals, including human animals35, have more or less the same metaphysical nature as other biological organisms. This is not to deny that some animals may have properties of considerable metaphysical interest – rationality and consciousness, for instance – that no plant or fungus could ever have. But if we ask what organisms are made of, what parts they have, whether they are concrete of abstract, whether and under what conditions they persist through time, and the like, I believe that the answer will be more or less the same for human organisms as it is for plants and fungi. So we need an account of the metaphysical nature of organisms generally.
I take it that organisms are concrete particulars. They are substances, and not events or states or aspects of something else. They persist through time; moreover they continue to be organisms when they persist. I will assume for the present that they do not have temporal parts, though we will revisit this assumption in chapter 5. I also assume that organisms are made up entirely of matter: they have no immaterial or non-physical parts. Descartes thought that each normal human animal36 was somehow attached to an immaterial substance that is necessary for a thing to think rationally, but not necessary for it to be alive in the biological sense. If this were true, I take it that the animal would be the material thing, and not the object made up of the material thing and the immaterial one.
Organisms differ from other material things by having lives. By a life I mean more or less what Locke meant (1975: 330-31): a self-organizing biological event that maintains the vastly complex internal structure of an organism. The materials organisms are made up of are intrinsically unstable, and must therefore be constantly repaired and renewed, else the organism dies and its remains decay. An organism must constantly take in new particles, reconfigure and assimilate them into its living fabric, and expel those that are no longer useful to it. An organism's life enables it to persist and retain its characteristic structure despite constant material turnover.
There may be things besides organisms that are in some sense alive: certain parts of organisms, such as arms, and things made up of several organisms, such as packs of wolves. They are not organisms because they lack lives of their own. My arm's tissues are kept alive by the vital processes of the human animal37 it is a part of: there is no self-organizing biological event of the right sort to be a life going on throughout my arm and nowhere else.
Organisms have parts: vast numbers of them. A thing is alive in the biological sense by virtue of a vastly complex array of biochemical processes, and the particles caught up in these processes are parts of the organism. (If Aristotle thought that organisms were mereologically simple, that is presumably because he thought that matter was homogeneous and not particulate.) Owing to metabolic turnover, organisms are made up of different parts at different times.
What are the parts of an organism? Where does an organism leave off, and its environment begin? Where an organism's boundaries lie has presumably to do with the spatial extent of its life. But just how its life determines its boundaries is not obvious. It is tempting to say that an organism is made up at a given time of just those particles that are caught up in its life – its metabolic activities – at that time. If you are an organism, you extend all the way to the surface of your skin and no further because that is the extent of your biological life. Your clothes, or a prosthetic limb, are not parts of you because damage to them is not repaired in the way that damage to your living fabric is repaired, because they are not nourished by your blood supply, because their parts are not renewed and replaced in the way that parts of your kidneys are, and so on. Neat though this view is, however, some find it too restrictive. They say that the particles in an animal's hair or in the dead heartwood of an ageing tree are parts of the organism, despite no longer being caught up in its life (Ayers 1991: 225). We needn’t settle this matter for present purposes.
As for identity over time, I am inclined to believe that an organism persists if and only if its life continues. This has the surprising consequence that an organism ceases to exist when the event that maintains its internal structure stops and cannot be restarted – that is, when the organism dies. Whatever is left behind – the organism's lifeless remains or its corpse or what have you – is something other than the organism. Strictly speaking, there is no such thing as a dead organism: no organism can be alive at one time and dead at another. I believe this because I have never seen a plausible alternative account of what it takes for an organism to persist (Olson 2004: 269-271). It is not a wholly eccentric view: in addition to Aristotle (see Furth 1988: 156-157) and Locke (1975: 330-331), it has several contemporary advocates (van Inwagen 1990: 142-158, Hoffman and Rosenkrantz 1997: 159, Wilson 1999: 89-99). It is controversial, however, and nothing I say in this book turns on it. The persistence conditions38 of human animals39 will concern us again in §§2.7 and 7.7.
Why suppose that we are animals? Well, there are about six billion human animals40 walking the earth – the same as the number of human people. For each of us there is a human animal41, and for every human animal42 (pathological cases aside, perhaps) there is one of us. Those animals are very like ourselves: they sit in our chairs and wear our clothes; they do our work and read our newspapers and chat with our friends. They appear to be so like us, both physically and mentally, that it is hard to tell the difference. These apparent facts pose a formidable obstacle to anyone who would deny that we are animals: the thinking-animal problem.
There is a human animal43 intimately related to you, which some call your body. Consider that animal’s mental properties. It would seem to have mental properties. You have mental properties, and the animal has the same brain and nervous system as you have (and the same surroundings too, if that is relevant). It went to the same schools as you did, and had the same teachers. It shows the same behavioral evidence of mentality as you do. What more could be required for a thing to have mental properties? In fact the animal seems to be mentally exactly like you: every thought or experience of yours appears to be a thought or experience on the part of the animal. How could you and the animal have different thoughts? But if the animal thinks your thoughts, then surely it is you. You could hardly be something other than the thing that thinks your thoughts.
Consider what it would mean if you were not the animal. The animal thinks. And of course you think. (We can’t suppose that the animal thinks and you don’t think. Nor can we suppose that you don’t exist, when your animal body thinks.) So if you were not that thinking animal44, there would be two beings thinking your thoughts: there would be the thinking animal45, and there would be you, a thinking non-animal. We should each share our thoughts with an animal numerically different from us. For every thought there would be two thinkers.
… (3) there is an animal there, and it thinks exactly as you do, but you are not it.
There is no fourth possibility. The repugnancy of these three alternatives seems to me a powerful reason to suppose that you are an animal. Let us consider them.
If you are not an animal, the reason may be that there is no animal that you or anyone else could be. How could there be no human animals47? What reason could anyone have for believing this?
A number of general metaphysical principles are incompatible with the existence of animals. For instance, some versions of idealism entail that there are no material objects at all (so I should describe those views, anyway); and if there are no material objects, then there are no biological organisms. But let’s not discuss idealism. Another example is the principle that nothing can have different parts at different times. According to this principle, whenever something appears to exchange an old part for a new one, the truth of the matter is that the object composed of the old parts ceases to exist (or else begins to disperse) and is instantly replaced by a new object composed of the new parts. Yet organisms by their very nature constantly exchange old parts for new ones. If nothing could ever survive a change of any of its parts, then organisms are metaphysically impossible; what we think of as an organism is in in reality only a series of "masses of matter" that each take on organic form for a brief moment- -until a single particle is gained or lost – and then pass that form on to a numerically different mass.
The principle that nothing can change its parts is both theoretically elegant and strikingly implausible (we will return to it in §§7.3-7.4). But few opponents of animalism48 deny the existence of animals. They have good reason not to: anything that would rule out the existence of animals would also rule out the existence of most of the things we might be if we were not animals. If there are no animals, then there are no beings constituted by animals, for instance, and no temporal or spatial parts of animals. And if nothing can change its parts, then persisting bundles of perceptions are no more possible than animals. If there are no animals, there will be few items remaining among the furniture of the earth that we might be.
The second alternative to our being animals is that the animals we call our bodies exist but don’t think in the way that we do. (Let any sort of mental activity or state count for present purposes as thinking.) There are two possibilities here: that human animals49 don’t think at all, and that they think but not as we do.
Consider first the idea that they don’t think at all. You think, but the animal sitting there doesn't. The reason for this can only be that the animal cannot think: it would certainly be thinking now if it were able to. And if that animal cannot think now, no human animal50 can ever think, for no human animal51 is better suited for thinking that it is. Presumably no biological organism of any sort could think. The claim, then, is that animals, including human animals52, are no more sentient or intelligent than stones; in fact they are necessarily incapable of thought. It may still be that most human animals53 relate in some intimate way to thinking beings – to us – and stones do not; and it might be appropriate for certain purposes to describe this fact loosely by saying that human animals54 are more intelligent than stones. But strictly speaking human animals55 would have no mental properties whatever.
That would be surprising. Human animals56 seem to think. Could this really be only a misleading appearance? If human animals57 and other organisms cannot think, there must surely be some impressive explanation of why they can’t – that is, some account of what prevents them from using their brains to think.
One possible explanation is that nothing can think: there is no such thing as thinking, any more than there is such a thing as phlogiston (a chemical substance once thought to be a constituent of solid matter and released in combustion). This view is known as eliminative materialism. But no opponents of animalism58 that I know of accept it. If it were true, it could not be the case that our identity through time consists in psychological continuity59, or that we have our mental properties essentially; and that would leave little reason to suppose that we are anything other than animals (see §§2.8 and 2.9).
Suppose eliminative materialism is false. In that case, the reason why human animals60 cannot think must presumably be that they have some property that prevents them from thinking – a property that we, who clearly can think, lack. (Or maybe they lack a property of ours that is necessary for thought.) The most obvious candidate for such a property is being material. If any material thing could ever think, surely it would be some sort of animal; so if animals cannot think, we should expect the reason to be that only an immaterial thing could think. You and I must therefore be immaterial. Of course, simply denying that any material thing could think does nothing to explain why it couldn't; but those who hold this view have said many things that would, if they were true, explain why no material thing could think. So you might expect anyone who denies that you and I are animals to deny that we are material things of any sort. But this is not so: many opponents of animalism61 claim to be materialists. They cannot explain human animals62' inability to think by appealing to the fact that animals are material.
They might say that human animals63 cannot think because they are mere bodies, and mere bodies cannot think. It could only be some sort of joke, the idea goes, to say that Newton’s body believed in absolute space, while Leibniz’s body disagreed. Since we think, it would follow that we are not our bodies, and therefore not animals. But that wouldn't mean that we are immaterial: we might be material things other than our bodies.
In any case, it is hardly an impressive argument against animal thought. I grant that there is something odd about the statement that Newton’s body believed in absolute space. But a statement can be odd without being false. Though it sounds preposterous to say that there is a liter of blood in my office, it is nevertheless true: I am in my office, and there is a liter of blood in me. The statement is odd because it suggests that blood is stored in my office in something like the way it is stored in blood banks, which really would be preposterous. The statement that Newton’s body believed in absolute space might be odd for a similar reason. For instance, the reason it sounds wrong might be that it suggests the false claim that believing in absolute space is in some sense a “bodily” property.
In any case, the oddness of saying that Newton’s body believed in absolute space should not lead us to infer that the phrase ‘Newton’s body' denotes something of Newton’s – a certain human organism – that was unable to think. Compare the word 'body' with a closely related one: mind. It is just as odd to say that Newton’s mind was tall and thin, or indeed that it had any other size or shape, as it is to say that Newton’s body believed in absolute space. But no one would conclude from this that Newton had some mental thing with no size or shape. That would be a poor argument for substance dualism. We cannot always substitute the phrase 'Newton’s mind' for the name 'Newton' without something going wrong; but it is doubtful whether any important metaphysical conclusion follows from this. We ought to be equally wary of drawing metaphysical conclusions from the fact that we cannot always substitute the phrase 'Newton's body' for the name 'Newton' without something going wrong.
Anyone who wants to explain why some material objects can think but animals cannot has his work cut out for him. I know of just two possible explanations worth considering. The first says that animals cannot think because they are too big. The true thinkers are brains, or perhaps parts of brains. A whole animal can be said to think only in the derivative sense of having a thinking brain as a part, much as a car is powerful in the sense of having a powerful engine as a part. Animals are stupid things inhabited by clever brains. I will take up this idea in Chapter 4.
The second, which is far more interesting, is due to Shoemaker (1984: 92-97, 1999, 2004). He says that animals cannot think because they have the wrong identity conditions. Mental properties, he says, have characteristic causal roles. For you to be hungry, for instance, is for you to be in a state that, among other things, is typically caused by your having low blood sugar, and which tends to cause you to act in ways you believe would result in your eating something nourishing. Now your hunger is a state that tends to combine with your beliefs – not mine – to cause you, and no one else, to behave in certain ways. That is part of the nature of hunger. More generally, for you to have any mental property is at least in part for you to be in a state disposed to combine with certain of your other states to cause you, and no one else, to do certain things.
But that, Shoemaker claims, is to say that any being whose later states or actions are caused in the appropriate way by your current mental states must be you. Now suppose your cerebrum66 is put into my head tomorrow. Then your current mental states will have their characteristic effects in the being who ends up with that organ, and not in the empty-headed thing left behind. The subject of those states – you – must therefore go along with its transplanted cerebrum67. It follows that psychological continuity68 of a sort must suffice for you to persist through time. More generally, the nature of mental properties entails that psychological continuity69 suffices for anything that has them to persist. Since no sort of psychological continuity70 suffices for any organism to persist – no human animal71 would go along with its transplanted cerebrum72 – it follows that no organism could have mental properties. The nature of mental properties makes it metaphysically impossible for animals to think. However, material things with the right identity conditions would be able to think. Shoemaker believes that human organisms typically "constitute" such things.
It is important to see just how surprising this view is. Suppose you and I are physically just like human animals73. (Shoemaker more or less accepts this.) Then the view implies that beings with the same physical properties and surroundings can differ radically in their mental properties. In fact this happens regularly: every human person coincides with an animal physically indistinguishable from her – a perfect physical duplicate – that has no mental properties whatever. There are physically identical beings, in identical surroundings, that differ as much in their mental properties as we differ from trees. Mental properties fail to supervene74 on physical properties in even the weak sense that any two beings with the same physical properties will have the same mental properties. A thing's having the right physical properties and surroundings does not even reliably cause it to have any mental properties.
I find Shoemaker’s argument against animal thought unpersuasive. It doesn’t seem absolutely necessary that the characteristic effects of a being’s mental states must always occur in that very being. In fact it seems that it would not be so in fission cases. Suppose your cerebrum75 is removed from your head and each half is implanted into a different empty head. Then your mental states have their characteristic effects in two different people. If the nature of mental states entails that the donor must be identical with the recipient in the “single” transplant76 case, it ought to entail that the donor must be identical with both recipients in the double transplant77. But that, as Shoemaker himself agrees, is impossible.
There is more to say about Shoemaker’s argument, but this is not the place for it (see Olson 2002a). What if human animals78 do think, but not in the way that we do? There are two possibilities here. One is that they have different mental properties from us: for instance, they are conscious but never self-conscious. The other is that human animals79 have the same mental properties as we have, but they have them in a different way: for instance, they think only in the derivative sense of relating in a certain way to us, who think in a straightforward and non-derivative sense80. By itself, however, neither of these suggestions does anything to solve the thinking-animal problem. It would be just as surprising if human animals81 were incapable of having the sorts of thoughts that we have, or if they could not think in the sense that we do, as it would be if they could not think at all. It would demand the same sort of explanation, and the prospects for finding one would be similar. It is hard to see what opponents of animalism82 would gain by proposing such a view.
Suppose human animals84 think in just the way that we do: every thought of yours is a thought on the part of a certain animal. How could that thinking animal85 be anything other than you? Only if you are one of at least two beings that think your thoughts. (Or maybe you and the animal think numerically different but otherwise identical thoughts. Then you are one of at least two beings thinking exactly similar thoughts.) If you think, and your animal body thinks, and it is not you, then there are two thinkers there, sitting and reading this book. Call this the cohabitation view. It is unattractive in at least three different ways.
Most obviously, it means that there are far more thinking beings than we thought: the overcrowding problem. Defenders of the cohabitation view – and it has its defenders – typically respond by proposing linguistic hypotheses. They propose that the things we ordinarily say and believe about how many people there are do not mean or imply what they appear to mean or imply. They interpret, or reinterpret, our ordinary, non-philosophical statements and beliefs in a way that would make them consistent with the cohabitation view. When I write on the copyright form that I am the sole author of this book, for instance, I might seem to be saying that every author of this book is numerically identical with me, which according to the cohabitation view is false. But it may not be obvious that that is what I mean. Perhaps I mean only that every author of this book bears some close relation to me: that they all share their thoughts with me, say, that they exactly coincide with me. In that case the ordinary statement that I am the sole author of this book comes out true, even if strictly speaking the book has at least two authors. My wife is not in any ordinary sense a bigamist, even if she is married both to me and to this animal. At any rate it would be badly misleading to describe our relationship as a ménage à quatre.
The general idea is that whenever two thinking beings relate to one another in the way we relate to our animal bodies, we "count them as one" for ordinary purposes (Lewis 1993). Ordinary people – people not engaged in metaphysics – have no opinion about how many numerically different thinkers there are. Why should they? What matters in real life is not the number of numerically different thinkers, but the number of non-overlapping thinkers. Human people and thinking human animals86 don’t compete for space. The world is overcrowded only in a thin, metaphysical sort of way and not in any robust quotidian sense.
If this is right, the cohabitation view is consistent with everything we ordinarily say and believe about how many of us there are. But that does not entirely deprive the overcrowding problem of its force. Philosophers of language who know their business can take any philosophical claim, no matter how absurd, and come up with a linguistic hypothesis according to which that claim is compatible with everything we say and think when we’re not doing philosophy. If I say that I had breakfast before I had lunch today, there is no doubt something I could be taken to mean that would make my statement compatible with the unreality of time. But that would not make it any easier to believe that time is unreal – not much, anyway. For the same reason, the mere existence of the hypothesis that we “count” philosophers by a relation other than numerical identity does little to make it easier to believe that there are two numerically different philosophers sitting there and reading this now. That is because that linguistic hypothesis seems to most of us to be false.
In any case, the troubles for the cohabitation view go beyond mere overcrowding. The view makes it hard to see how we could ever know that we were not animals. If there really are two beings, a person and an animal, now thinking your thoughts, you ought to wonder which one you are. You may think you're the person – the one that isn't an animal. But since the animal thinks exactly as you do, it ought to think that it is a person. It will have the very same grounds for thinking that it is a person and not an animal as you have for believing that you are. Yet it is mistaken. If you were the animal and not the person, you would still think you were the person. So for all you know, you are the one making the mistake. Even if you are a person and not an animal, it is hard to see how you could ever have any reason to believe that you are87. Call this the epistemic problem.
The cohabitation view is unattractive in a third way as well. If your animal thinks just as you do, it ought to count as a person. It satisfies every ordinary definition of 'person': it is, for instance, "a thinking intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing, in different times and places," as Locke put it. But no one supposes that your animal body is a person numerically different from you – that we each share our thoughts with another person. If nothing else, that would contradict the popular claim that people – all people – have properties incompatible with those of animals (see §2.7 below). It would also mean that some human people are animals, even if others are not. And if human animals88 are not only psychologically indistinguishable from ourselves but are also people in their own right, it is even more difficult to see how anyone could have any reason to believe that she was not one of the animal people.
If ordinary human animals89 are not people, on the other hand, despite having the same mental properties as people, all familiar accounts of what it is to be a person are too permissive. There could be non-people whose inner life was entirely indistinguishable from ours; indeed, there would be at least one such non-person for every genuine person. That would deprive personhood of any psychological or moral significance. For that matter, it would make it a real epistemic possibility that we are not people. I can verify easily enough that I am rational, self-conscious, and so on; but how could I assure myself that I have that extra feature required for personhood that rational human animals90 lack? Call this problem – that our animal bodies would be people different from ourselves – the personhood problem.
Some say that the epistemic problem has a linguistic solution (Noonan 1998, forthcoming). They make two surprising claims. First, they say, not just any rational, self-conscious being, or more generally any being with our mental capacities, is a person. To count as a person, a thing must have not only the appropriate mental qualities, but something else as well: it must persist by virtue of psychological continuity91, or have those mental qualities essentially, or the like. Call this extra feature F. That beings must have F in order to fall within the extension of the word ‘person’ is supposed to be a contingent fact about how we use that word. Human animals92 lack F, and therefore do not qualify as people, despite being psychologically indistinguishable from ourselves. That is the first claim. The second is that the word 'I' and other personal pronouns, at least in their most typical uses, refer only to people: that's why we call them personal pronouns. A being that says 'I' in normal circumstances refers thereby to the person who says it. This too is supposed to be a contingent fact about how we use language.
These two claims, together with the cohabitation view, yield the startling conclusion that first-person utterances (and presumably first-person thoughts as well) do not always refer to the beings that utter or think them. In particular, when your animal body says 'I', it doesn't refer to itself, as it isn't a person. But presumably you have F; so you are a person, and when you say or think 'I', you do refer to yourself. Since your animal body says and thinks just what you say and think, its first-person utterances and thoughts therefore refer to you – the person who produces them – rather than to itself. If it says, "I am hungry," it means not that it iself is hungry, but that you are. More to the point, if the animal says or thinks, "I am a person and not an animal," it does not say falsely that it is a person and not an animal, but truly that you are. So neither you nor the animal is mistaken about which thing it is.
Call this linguistic hypothesis – that personal pronouns refer only to people and that people by definition have F – personal-pronoun revisionism. How would it solve the epistemic problem? Suppose there are two beings thinking your thoughts: an animal, and also a nonanimal with psychological persistence conditions93 – a psychological continuer for short. Better, suppose that you know this. Suppose further that having psychological persistence conditions94 is the extra person-making feature F. Now imagine wondering which of the beings thinking your thoughts you are, the animal or the psychological continuer. How could you work out the answer to this question?
Well, as a competent speaker of English you would know at least implicitly (1) that each occurrence of the word 'I' refers only to the person who utters it. You would also know, or be able to work out, (2) that something counts as a person only if it is a psychological continuer, which according to pronoun revisionism is true by definition. And of course you know (3) that you are whatever you refer to when you say 'I'. These are supposed to be linguistic and conceptual facts that we can know a priori. Given that a psychological continuer thinks your thoughts, it follows from these claims (4) that you are a person and a psychological continuer. If you know that animals are not psychological continuers, you can infer from this that you are not an animal – even if you share your thoughts with an animal psychologically indistinguishable from you. You can therefore know that you are a psychological continuer and not an animal. You can know which of the beings thinking your thoughts you are. That would solve the epistemic problem.
There is much to be said about this proposal (I discuss it at greater length in Olson 2002b; see also Zimmerman 2003: 502-503). I will make just one comment. We are supposing that the human animals95 that walk and talk and sleep in our beds have the full range of human attitudes and emotions, and are psychologically indistinguishable from ourselves96. (We discussed the view that human animals97 are psychologically different from ourselves in the previous section.) Now consider your understanding of the word ‘person’. In particular, think of the sense of the word that informs your use of the personal pronouns. What features must a being have in order for you to call it a person in that ordinary sense? What must it have in order to be a someone rather than a something, a he or a she rather than an it? If something were psychologically indistinguishable from yourself, or from one of your close friends, would you refuse to call it a person or a someone until you were told whether it persists by virtue of psychological continuity98? That seems to be no part of what we ordinarily mean by ‘person’. If human animals99 really are psychologically just like ourselves, they will count as people in any ordinary sense of the word. It couldn’t turn out that half of the rational, self-conscious, human-sized beings that we know and love and interact with in daily life are not people. Human animals100 may fail to satisfy some specialized philosophical sense of ‘person’, owing to their having the wrong persistence conditions101 or on some other trivial grounds. But they are surely people in the sense of the word that informs our ordinary use of the personal pronouns.
Maybe it isn’t always clear to us what we mean by our words. Some ordinary words may mean something very different from what they seem to mean. Perhaps we cannot dismiss personal-pronoun revisionism as absurd. But it is hardly part of an attractive alternative to animalism102.
Those who say that we are not animals will probably want to argue either that human animals104 cannot think in the way that we can, or that we can somehow know that we are not the human animals105 that share our thoughts. Neither prospect looks promising. That, to my mind, is the principal case for our being animals. What is the case against it?
Historically, the main reason for denying that we are animals is hostility to materialism. The conviction that no material thing, no matter how complex, could ever think in the way that we do is clearly incompatible with our being animals. But few philosophers set much store by it nowadays. The main contemporary objection to animalism106 has to do with our identity over time, the most popular account of which is that we persist by virtue of some sort of psychological continuity107. That rules out our being animals, for no sort of psychological continuity108 is either necessary or sufficient for a human organism to persist.
To see that it isn’t necessary, consider the fact that each human animal109 starts out as an embryo110 incapable of any sort of mental activity. There is no psychological continuity111 of any sort between an adult human animal112 and the embryo113 it once was: the adult animal’s mental properties cannot derive in any way from those of the embryo114, for the embryo115 had none. The embryo116 is the adult human organism, yet there is no psychological continuity117 between the embryo118 as it started out and the full-grown animal as it is today. A human animal119 can therefore persist without any psychological continuity120 whatever. Or consider what would happen if you were to lapse into a persistent and irreversible vegetative state. The result of this would be a human organism that was clearly alive, in the biological sense in which an oyster is alive: it would breathe spontaneously, digest its food, fight infection, heal wounds, and so on. It would presumably be the very human organism that was once able-bodied: no one supposes that a human animal121 that lapses into a persistent vegetative state122 thereby ceases to exist and is replaced by a new animal. But the animal would no longer be capable of any mental activity. Again, a human animal123 can persist despite complete psychological discontinuity. If any sort of psychological continuity124 is necessary for you to persist, then your animal body existed before you did, and it could outlive you. But nothing existed before it itself existed, and nothing can outlive itself. It follows that you are not that animal.
Now the claim that psychological continuity125 is necessary for us to persist may sound unattractive. Those who have actually suffered the misfortune of having a loved one lapse into a persistent vegetative state126 do not often believe that that person has literally ceased to exist, and that the living thing lying on the hospital bed is a numerically different being. (They may say that their loved one’s life no longer has any value, or that he ought to be allowed to die; but that is another matter.) Nor does this attitude appear to rest on the mistaken belief that there is some sort of psychological continuity127 in these cases. And when we see an ultrasound picture of a 12-week-old foetus128, most of us are inclined believe that we are seeing something which, if all goes well, will come to be a full-fledged human person, even though it now has no mental properties. (This is something that most parties to debates over the morality of abortion129 agree on.) We don’t ordinarily suppose that the foetus130 cannot itself become a person, but can only give rise to a person numerically different from itself.
In fact animalism131 appears to be compatible with everything we believe about our persistence in real-life situations. In every actual case, the number of people we think there are is the same as the number of rational human animals132. Every actual case in which we take someone to survive or perish is a case where a human animal133 survives or perishes. Or at least this is so if we leave aside religious beliefs – our being animals may be incompatible with our being resurrected or reincarnated (though some leading philosophers of religion disagree: see van Inwagen 1978, Zimmerman 1999, Merricks 2001a).
But animalism134 conflicts with things we are inclined to say about science-fiction stories. This appears to show a deep and widespread conviction that some sort of psychological continuity135 is sufficient for us to persist.
Imagine that your cerebrum136 is put into another head. The being who gets that organ, and he alone, will be psychologically continuous with you on any account of what psychological continuity137 is: he will have, for the most part anyway, your memories, beliefs, and other mental contents and capacities; he will have your “first-person perspective”; he will take himself to be you; all these mental properties will have been continuously physically realized throughout the process; and there are no troublesome rival claimants. If any psychological facts suffice for you to persist, that being would be you: you would go along with your transplanted cerebrum138. And many people are convinced that you would indeed go along with your transplanted cerebrum139.
What about your animal body? Would it go along with its cerebrum140? Would the surgeons pare that animal down to a lump of yellowish-pink tissue, move it across the room, then supply it with a new head, trunk, and other parts? Surely not. A detached cerebrum141 is no more an organism than a detached arm is an organism: if the animal went along with the cerebrum142, it would have to cease being an animal for a time and then become an animal once more when the transplant143 is complete. More importantly, think of the empty-headed thing left behind when your cerebrum144 is removed. It is an animal. If the surgeons are careful to leave the lower brain intact, it may even remain alive. It seems to be the very animal that your cerebrum145 was a part of before the operation. The empty-headed being into which your cerebrum146 is to be implanted is also a living human organism. And putting your cerebrum147 into its head surely doesn’t destroy that organism and replace it with a new one.
So there appear to be two human animals148 in the transplant149 story. One of them loses its cerebrum150 and gets an empty head. That organ is then fitted into the empty cranium of the other animal, which is thereby made whole again. The surgeons move an organ from one animal to another, just as they might do with a liver. No animal moves from one head to another. Even though there is full psychological continuity151 between the cerebrum152 donor and the recipient, they are not the same animal. Thus, no sort of psychological continuity153 suffices for a human animal154 to persist through time. One human animal155 could be psychologically continuous in the fullest possible sense with another human animal156.
The conviction that you would go along with your transplanted cerebrum157 is therefore incompatible with your being an animal. Your animal body would stay behind if your cerebrum were transplanted158. If you would go along with your transplanted cerebrum159, then you and that animal could go your separate ways. And of course a thing and itself can never go their separate ways. It follows that you are not that animal, or indeed any other animal. Not only are you not essentially an animal. You are not an animal at all, even contingently: nothing that is even contingently an animal would move to a different head in a cerebrum transplant160.
So the principal case against animalism161 is this: If we were animals, we should have the persistence conditions162 of animals, conditions which have nothing to do with psychological facts. Psychology would be completely irrelevant to our identity over time. Cerebrum transplants163 would be no different, metaphysically, from liver transplants164: you could donate your cerebrum165 to someone else, just as you could donate your liver. But that is absurd. Psychology clearly is relevant to personal identity. You would go along with your transplanted cerebrum166; you wouldn’t stay behind with an empty head. Therefore we are not animals.
Taken in isolation, the transplant167 argument may look strong. Why deny that we should go along with our transplanted cerebrums168? Isn’t it obvious that that is what would happen? But we have seen how this “transplant169 conviction” could be wrong: it would be wrong if we were animals. Would it really be so surprising if it were wrong? To my mind, it would be surprising if it were right. That would mean either that human animals170 cannot think, or that you are one of two beings thinking your thoughts, and one of those beings would not go along with its transplanted cerebrum171. That would be surprising.
In any case, there are other reasons to doubt the transplant172 conviction. For one thing, the sort of psychological continuity173 that would hold between you and the recipient of your cerebrum174 could hold between you and two future beings. If your cerebrum175 were divided and each half implanted into a different head, at least one of the resulting beings would be mistaken in thinking that she was you, for the simple reason that one thing (you) cannot be numerically identical with two things176. Someone can be fully psychologically continuous with you and yet not be you: psychological continuity177 is not sufficient for us to persist. That undermines the judgment that the one mentally continuous with you in the original transplant178 story would be you. If the claim that anyone psychologically continuous with you must be you fails to hold in fission cases, it might fail to hold in cerebrum transplants179 too.
For another, the transplant180 conviction gets much of its support from a questionable assumption about our practical attitudes – "what matters181 in identity", as the jargon has it. Imagine that your cerebrum182 is about to be transplanted183 into my head. The empty-headed being left behind will then get a new cerebrum184. The hospital has only enough morphine for one of the two resulting people; the other will suffer unbearable pain. If we asked you before the operation who should get the morphine, how would you choose? (Imagine that your motives are entirely selfish.) Most people say that you would have a strong reason to give the morphine to the one who ends up with your cerebrum185. You would have less reason, if any, to give it to the other person. This may lead us to infer that you would be the one who ends up with your cerebrum186.
But this inference is questionable. Many philosophers doubt whether your selfish interest in the welfare of the person who gets your cerebrum187 must derive from the fact that he or she is you. In the double-transplant188 case, they say, you would have a selfish reason to care about the welfare of both offshoots. Better, you would have the same reason to care about the fission offshoots as you would have to care about the one who got your whole cerebrum189. Yet neither of the fission offshoots would be you. In that case the concern you would have for the person who got your cerebrum190 in the single transplant191 case would not support the claim that he or she would be you, thus depriving the transplant192 conviction of what appears to be its principal support193.
If the transplant194 conviction is false, why did anyone ever accept it? Well, someone’s being psychologically continuous with you is strong evidence for her being you. Conclusive evidence, in fact: no one is ever psychologically continuous with anyone other than herself in real life. That makes it easy to suppose that the one who gets your cerebrum195 in the transplant196 case would be you, even if, because we are animals, it isn’t so.
Here is another reason why someone might find the transplant197 argument a conclusive refutation of animalism198. Suppose there are, in addition to human animals199, thinking non-organisms that would go along with their transplanted cerebrums200, or more generally beings that persist by virtue of some sort of psychological continuity201. And suppose that such a being thinks your thoughts. Then there would be two beings that are otherwise equally good candidates for being you, except that one has the sort of persistence conditions202 we believe you to have and the other (the animal) doesn’t. Would it not be perverse, in that case, to suppose that you are the second being? That would make animalism203 look plainly wrong. I believe that many advocates of the transplant204 argument do assume that certain non-animals think our thoughts. Few of them give any reason to accept that metaphysical claim, however, and some such reason is surely needed. We will consider some reasons for it in Chapters 3 and 5. But even if assuming that human animals205 coincide with thinking non-animals would make the transplant206 argument an irresistible attack on animalism207, it would not make it a strong argument for any positive view about what we are208. That is because of the thinking-animal problem: the difficulty of knowing that we are anything other than the animals thinking our thoughts.
Note the electronic version is paged backwards!
We have seen that animalism209 conflicts with traditional thinking about our identity over time. Here are some further objections.
First, animalism210 seems to imply that you and I are only temporarily and contingently people. At least this is so on most proposed accounts of what it is to be a person. Every human animal211 was once an embryo212 with no mental properties. If being a person implies having certain mental properties – rationality and self-consciousness213 or the like – then each human animal214 was once a non-person. Even if a thing need only have the capacity to acquire the relevant mental properties in order to count as a person, so that unthinking embryos215 might be people, human animals216 in a persistent vegetative state217 will not count as people, and any human animal218 could end up in such a state.
I don’t want to argue about what it is to be a person. (I don’t find it an interesting question.) The important fact is that our being animals would make our having mental features of any sort a temporary and contingent condition of us – even if it is our normal or proper condition. It would mean that any of us could exist at a time without having any mental properties whatever at that time, or even the capacity to acquire them. What is more, any of us could have existed without having any mental properties at any time: any of us could have died six weeks after conception. Your being able to think or experience would be no more essential to you than your being a philosopher. It would not, so to speak, be part of your being.
Second, animalism219 appears to entail that there are no persistence conditions220 for people as such: no persistence conditions221 that necessarily apply to all people and only to people. The persistence conditions222 of human animals223 presumably derive from their being animals, or organisms. That makes their persistence conditions224 no different from those of oysters, which are not people by anyone’s lights. If so, then our being animals implies that we have the same persistence conditions225 as some non-people. Animalism226 is also consistent with there being people whose persistence conditions227 are different from ours: inorganic people such as gods or angels, for instance. If there could be such beings, it would not be necessary that all people have the same persistence conditions228. People’s persistence conditions229, and for that matter their metaphysical nature in general, would derive not from their being people, but from their being animals, or immaterial substances, or whatever metaphysical sort of person they are. Person would not be a kind that determines the identity conditions of its members.
Some philosophers see in these implications a grave objection to animalism230 (Baker 2001: 218-20). They find it absurd to suppose I might be a person only temporarily and contingently. We might as well say that the moon is only temporarily and contingently a material object. This thought appears to be incompatible with our being animals.
The claim that there are no persistence conditions231 for people as such is said to conflict with the very idea of personal identity (Baker 2001: 124). To think about personal identity, the objection goes, is to inquire into the identity conditions of people as such – identity conditions that things have by virtue of being people. That, they say, is why we call it personal identity. If there are no such conditions, as animalism232 seems to imply, then there is no such thing as personal identity – an implication that is also taken to be absurd.
I suppose these objections have some force. That you and I are people essentially is an attractive claim. But it doesn’t seem obvious. If we take seriously the idea that a person could be an organism, and we accept that organisms have mental properties only contingently, and we take being a person at a time to entail having mental properties at that time, then we can understand well enough how someone might be a person only contingently. And if nothing else, the thinking-animal problem shows that our being organisms is a claim that we must take seriously.
That we must have our persistence conditions233 by virtue of being people, so that there must be persistence conditions234 for people as such, is another interesting conjecture. Here is how I see it. You and I have many important properties. We are people. We are also (let us suppose) material, composed of parts, biologically alive, sentient, and awake. For that matter, we might also be philosophers, Hindus, women, or Ukrainians. What principle dictates that our being people must determine our identity conditions, rather than any of these other properties? None that I know of. It may be plausible on the face of it; but its incompatibility with our being animals looks like an excellent reason to doubt it.
One further objection to animalism235 is that it implies the wrong account of what determines how many of us there are at any one time (Lowe 1996: 31) – a topic sometimes called "synchronic identity". If we are animals, then the number of human people at any time will always be equal to the number of human animals236 that have whatever it takes to be a person at that time. And what determines the number of animals is presumably a matter of brute biology. Perhaps it is determined by the number of biological lives in the sense sketched in §2.2. But many philosophers, beginning with Locke, have assumed that the number of people or thinking beings at any given time is determined not by brute biology but by psychological facts: facts about mental unity and disunity.
My mental states are unified in the sense of being disposed to interact with one another, and not with any others, in an especially direct way. For instance, my desire to get a train to London will tend to combine with my belief that this train goes to London to cause me to board it. My desires don't interact with your beliefs in this way to produce action. That, the idea goes, is what makes it the case that my desires and my beliefs are the states of a single person, whereas my desires and your beliefs are not. More generally, mental states belong to the same person or thinking being just when they relate to one another in this way (Shoemaker 1984: 94- 97). So the number of people, or thinking beings generally, is necessarily equal to the number of unified systems of mental states. Call this the psychological individuation237 principle.
This principle looks incompatible with animalism238. It seems possible for an animal to have disunified mental states – supposing that an animal can think at all, anyway. It may even be possible for an animal to have a mental life that is no more unified than yours is with mine: perhaps a single human animal239 could be the home of two unified mental systems. This might happen in an extreme case of multiple personality – not in any actual case, but in a case that we could imagine by extrapolating from actual cases. The psychological individuation240 principle implies that such an animal would be the home of two people.
This doesn't yet show that the psychological individuation241 principle conflicts with animalism242. Animalism243 doesn't say that all people are animals. Why couldn't we normal human beings be animals, while people with extreme split personality are something else? But that would be an uncomfortable view. What sort of things would the people in those unusual cases be? They must be something. Perhaps they would be bundles of mental states, or parts of brains. But if an animal with split personality could house two or more such non-animal people, we should expect your animal (which I take to be normal and mentally unified) to house one non-animal person. And if there is a non-animal person within you, it will be hard to maintain that you are the animal. How could you ever know which person you are? Animalism244 at least strongly suggests that for every animal there can be at most one human person, no matter how disunified that animal's mental states might be; and that appears to be incompatible with the psychological individuation245 principle.
As I see it, the psychological individuation246 principle is yet another debatable conjecture (Olson 2003). In §6.4 I will argue that it is incompatible with our being material things of any sort, and is best combined with the view that we are bundles of mental states.
I believe that the most serious worries for animalism247 are very different from those we have considered here. We will come to them in Chapter 9248. In the meantime let us turn to the other views of what we are249.
Footnote 12: Advocates of animalism include Carter (1989), Ayers (1990: 283-285), Snowdon (1990), van Inwagen (1990), Hoffman and Rosenkrantz (1997), and Merricks (2001a, 2001b). See also Olson 1997a and 2002a.
Footnote 80: Baker combines these proposals (2000: 12-18, 68n., and 2002: 42). She says that human animals have thoughts requiring a “first-person perspective” only in the derivative sense of constituting non-animals (ourselves) that have them non-derivatively, while the opposite is the case for other thoughts: human animals have them non-derivatively and we have them derivatively.
Footnote 87: Someone might think that this problem arises only on an "internalist" epistemology. If you are the person and not the animal, the idea would go, then your belief that that is what you are is guaranteed to be true, and so is reliably formed, and so counts as knowledge. I don't think any serious epistemologist would endorse this reasoning. Suppose I come to believe, in an insane delusion, that I am Napoleon. And suppose I am in fact Napoleon reincarnated. Finally, suppose that who I am has no influence on who, in my demented state, I believe myself to be. Then my belief is guaranteed to be true; yet it has no epistemic virtue whatever, and certainly doesn’t count as knowledge.
Footnote 96: Could a being that cannot refer to itself in the first person be self-conscious? Well, pronoun revisionists agree that human animals have first-person thoughts just like our own. All that prevents them from referring to themselves in the first person, the idea goes, is the contingent linguistic fact that we (and they) use the personal pronouns to refer only to psychological continuers. We could change the way we talk, so that our personal pronouns referred only to beings with animal persistence conditions. If we did that, we should be unable to refer to ourselves in the first person, though our mental lives would otherwise remain unchanged. Would that deprive us of our capacity for self-consciousness? Not in any important sense, surely. Someone might point out, however, that according to pronoun revisionism a human animal could not “think of itself as itself”, and would therefore fail to satisfy Locke’s definition of ‘person’.
Footnote 156: Although I am not sure whether I have understood them, Wiggins (1980: 160-163) and McDowell (1997: 237) seem to disagree with me about this. For more on this matter see Olson 1997a: 109-119, and §7.7 below.
Footnote 176: Advocates of the temporal-parts view have a way of denying this claim: see §5.7.
Footnote 193: I say more about this in Olson 1997a: 52-70. Whether any of these claims about what matters in identity are true is another matter.
Footnote 248: For more objections to animalism see Baker 2001: 12-18 and 122-124, Snowdon 2003, Olson 2004, and Hershenov 2005.

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