The Sussex probationary officer was working undercover, patrolling an area plagued by a recent string of burglaries, when CCTV operators alerted him to a suspect nearby. Following the operators’ directions on his radio, the officer set off to apprehend the man. He ran down one alleyway after another, but the suspect was nowhere to be found. Still the operators continued to insist that the suspect was just around the corner, if only the officer could catch up. The pursuit continued for some twenty minutes until a sergeant entered the control room and recognized the ‘suspect’ on the monitor. A senior officer recounts what followed: ‘With the sergeant's sides aching from laughter he pointed out to the PC that the operator had been watching him unaware that he was a plain-clothes officer – thus the PC had been chasing himself round the streets.’Footnote ¹ The chase was called off.

I draw your attention to this (apparently true) story, not to point out the limitations of CCTV as a tool for crime prevention, but to illustrate an interesting philosophical distinction. The distinction is between two ways in which we can think about, or be aware of, ourselves. Sometimes the awareness we have of ourselves is not unlike our experience of other objects or people in our environment. I read a bio of myself on my department's website, I watch an old home movie of myself as a child, I catch my reflection in a mirror in a crowded restaurant, I hear my voice on my outgoing voicemail message. In these cases, the person I see, hear, or read about happens to be me. But it could have been someone else. Watching a video of myself is a lot like watching a video of a friend or relative. Hearing myself on a voicemail message is not so different from hearing the voice of another person. And it is possible in such cases for me to mistake myself for someone else. I wrongly assume that the child in the home movie is my cousin. I intend to call my parents, but accidentally dial my own number and momentarily mistake my voice on the outgoing voicemail message for the voice of my mother. The restaurant is crowded and I mistake my image in the mirror for an image of another (similar-looking) patron. In these cases, I am aware of myself insofar as I am aware of someone who happens to be me. But I am not aware of myself as myself: I do not realize that the person I am aware of is me. It was this sort of mistake that the Sussex officer made as he was ‘chasing himself round the streets’. If, in his frustration, the officer had muttered, ‘Where is that guy?’ he would have been talking about himself. He was ‘that guy’, despite his failure to realize it.

When it comes to things and people we observe in our environment, we make errors of misidentification all of the time. Watching a man stagger down the street, I remark, ‘Charlie had too much to drink’. It turns out that I am right that someone had too much to drink, but I am wrong that the man is my acquaintance, Charlie. I see a red station wagon on the street with its windshield smashed in and conclude that my car has been vandalized. While I am correct that some car has been vandalized, I am wrong to conclude that the vandalized car is mine. This is what distinguishes errors of misidentification from other types of errors. In the case of misidentification, one still knows that something (or someone) is thus and so, despite the fact that one is wrong about what (or who) it is. Compare this to a different kind of mistake: in a hallucinatory fog after a night of heavy drinking, Charlie thinks he sees his dead father standing in the doorway. In this case, Charlie is not even correct that someone is in the doorway. Charlie has made a mistake, but it is not a mistake of misidentification.

Errors of misidentification are common when it comes to other people and objects; they happen much less frequently when the person in question is oneself. Mistaking oneself for someone else (or someone else for oneself), when it does happen, can be comical and newsworthy, as we have seen in the case of the officer from Sussex. It tends to happen when we are aware of ourselves in a ‘third person way’: we see ourselves as other people see us, or as we see other people.

Let us turn now to the other way in which we are aware of ourselves. This second way is much less newsworthy. It is the way we are aware of ourselves most of the time. And yet philosophers have found it utterly baffling. Suppose I have a headache. It doesn't seem possible for me to misidentify the person who has the headache as myself, or conversely, to misidentify myself as someone else. In other words, it would be ridiculous for me to say, ‘Well, someone has a headache, but is it me who has a headache?’ I couldn't be right that someone has a headache, but wrong that the person who has a headache is me. Neither would it make sense to suppose that, while I have a headache, I mistakenly believe that the person with the headache is someone else. Here are some other examples: I see a table, I am thinking about a prime number. It is not possible for me to be correct that someone sees a table, or that someone is thinking about a prime number, but wrong that the person in question is me. I could, of course, be wrong that it is a table that I see, or that the number I am thinking about is actually prime. The point is that I couldn't be wrong that it is me who is doing the seeing or thinking. In this respect, these kinds of judgements we make about ourselves are often said to be immune to error through misidentification.

Philosophers have typically considered immunity to error through misidentification to be a mark of self-consciousness. First-person judgements that lack this sort of immunity are still about oneself, but they do not necessarily involve awareness of oneself as oneself: there is an important difference between awareness of someone who happens to be oneself and awareness of oneself as oneself. Ludwig Wittgenstein, writing in the mid-twentieth century, characterized the distinction as a distinction between the ‘use of ‘I’ as object’ and the ‘use of ‘I’ as subject:

While Wittgenstein put the distinction in terms of the use of the word, ‘I’, we can also think of the distinction as one between two ways of being aware of ourselves. The officer, hearing the description from the CCTV operator, was aware of himself as object. But in countless other ways, he was also aware of himself as subject. Perhaps, as the officer ran through the streets, he began to feel fatigued. Perhaps he looked forward to a cold beer after his shift. These are ways in which he could be aware of himself as subject. It would be quite odd for him to say, ‘I know that someone is tired, but is it me who is tired?’ Or, ‘I know that someone wants a drink, but is it me who wants a drink?’

Philosophers have puzzled over why genuine self-awareness should be immune to error through misidentification. What is special about us, or about the way in which we are aware of ourselves when we are self-conscious, that makes it impossible for us to misidentify ourselves? What exactly guarantees that we pick out the right person when we are self-conscious? Some philosophers have tried to explain the guarantee by claiming that the self is a very special sort of thing: it is not something physical that takes up space, and it is certainly not the same thing as one's body. Rather, the self is, as Descartes famously put it, ‘a thinking thing’: an immaterial soul or pure ego. We identify material bodies by their physical characteristics: I distinguish my car from others of the same make and model by the dent on its right fender, I recognize my friends by how they look and behave. When we identify something by its physical features, there is always the chance that something else has those very same features. Other cars might have dents in the same place. My friend might have an identical twin. Hence the possibility of misidentification. If self-consciousness, by contrast, is the awareness of something immaterial, rather than physical, then presumably self-consciousness would not be a matter of recognizing ourselves by means of some distinctive physical feature. This might help to explain why, when we use ‘I’ as subject, we do not have to worry about errors of misidentification. The thought is that we have a special sort of awareness of our own minds that is fundamentally different from the awareness we have of any material body.

While Wittgenstein understood the temptation of this view, he – along with some of his followers – found it ultimately unappealing. One concern is that it seems simply to replace one mystery with another. After all, are we really aware of something immaterial when we are self-conscious? Hume, writing two centuries before Wittgenstein, puts the worry as follows:

Hume is saying that when he introspects, all he finds are particular feelings, experiences, thoughts, emotions – these are what Hume calls ‘perceptions’. He does not find any immaterial subject or mind that has those perceptions. Hume reacted to his failure to locate an immaterial self by simply redefining the self as the collection or ‘bundle’ of those fleeting perceptions. We are not, according to Hume, subjects who have feelings, experiences, thoughts and emotions; rather, we are those feelings. Think about all the things going through your mind right now: the image of the words on this page, the internal monologue as you read those words quietly to yourself, the buzz of conversation in the café where you sit reading this. Hume's point is that these thoughts and experiences do not belong to you; they are you. In fact, Hume would have corrected me when I told you just now to focus on what's ‘going through your mind’ – there is no mind for anything to go through!

Instead of identifying the self with a bundle of thoughts and experiences, Wittgenstein and some of his followers went even further: they argued that statements in which ‘I’ is used as subject are not about anyone or anything at all. These philosophers thought that statements like ‘I am in pain’ have a completely different structure than ordinary declarative statements. Take ‘The book is red’. As any grade-schooler should know, the sentence has a subject term – ‘The book’ – and a predicate term, ‘is red’. The subject-term refers to something: in this case, a particular book. The predicate term says something about the thing to which the subject term refers: in this case, that it is red. The sentence, ‘I am in pain’ seems on the face of it to have a similar subject-predicate structure: ‘I’ looks like a subject term that refers to me, while ‘am in pain’ looks like a predicate that says something about me. But in this case appearances are misleading. ‘I’ does not, in fact, refer to anything at all. Wittgenstein says, ‘To say “I have pain” is no more a statement about a particular person than moaning is.’ The eighteenth-century German thinker Georg Christoph Lichtenberg had a nice analogy: the sentence ‘It is raining’ may look on the surface like a subject–predicate sentence, but we all know that the ‘it’ does not actually refer to some thing that is doing the raining. It would be more accurate (though less elegant) to say that raining is going on. In the same way, it would be more accurate to say that pain is going on.

Both the Humean and the Wittgensteinian view would explain why, when we use the word ‘I’ as subject, we do not have to worry about the possibility of misidentification. Suppose I am having a root canal and the Novocain wears off before the end of the procedure. If Hume is right that I just am the feeling of pain, along with all of the other perceptions I am having (the dentist leaning over me, the reflection of my gaping mouth in her glasses, the piercing sound of the drill …), then there is no sense to be made of the idea that I could be wrong about whose pain it is. It would make no sense for me to ask, ‘Someone is in pain, but is it me who is in pain?’, since there is no me distinct from that feeling of pain in the first place. And if Wittgenstein is right that the word ‘I’ does not refer to anything at all, then it would seem that there is no danger of referring to the wrong thing. I do not have to worry about mistaking someone else for myself when I use the word ‘I’, if ‘I’ is not meant to pick out anyone to begin with.

Many philosophers, however, find these views deeply unsatisfying. It is difficult to rid ourselves of the intuition that thoughts, sensations, and experiences do not simply float around by themselves in psychological space. They belong to us. We have them. John McDowell nicely puts it, ‘it is quite doubtful that we can really conceive thinking as a subjectless occurrence, like a state of the weather’.Footnote ⁴ These philosophical views about the self (or, more accurately, the lack thereof!) feel like theories of last resort. They are not all that appealing on their own. Philosophers are drawn to them only out of frustration with the other options on the table.

What exactly are we conscious of when we are self-conscious? It seems so far that we must choose between two unattractive answers. On one hand, we have the view that we are conscious of an immaterial soul. On the other, we have the view that there is no such thing as a self at all and that we are conscious only of our own thoughts and sensations. Some contemporary philosophers, most notably the late Gareth Evans, have argued that this choice is forced on us only because we have been too quick to dismiss a third possibility: that when we are self-conscious, we are conscious of ourselves as flesh and blood, embodied human beings. Let us recall for a moment why philosophers had initially dismissed this idea. We identify material objects and people by their distinctive physical features. Because it is possible that more than one thing could have those features, the judgements we make about material objects are vulnerable to the possibility of misidentification. So how could the judgements we make about ourselves when we are self-conscious be immune to these kinds of mistakes if the self that we are conscious of is something material?

Evans argued that this line of reasoning overlooks the fact that we can also have knowledge about physical aspects of ourselves that is immune to error through misidentification. I know, for example, that I am hunched over at my desk, typing on my laptop. My legs are crossed, my elbows are bent, my fingers are resting lightly on the keyboard. I know these things because I see my desk and laptop in front of me, I feel the keys beneath my fingertips. I have bodily sensations that inform me of the position of my digits and limbs. It would certainly be odd in this case to say that I know that someone is sitting behind a desk, but wrong that the person in question is me. Or that I know that someone's legs are crossed, but I am mistaken about whose legs they are. This is not to say that a sentence like, ‘My legs are crossed’ is always immune to error through misidentification; it depends on how I come to believe that the sentence is true. If I believe it because I am looking in a mirror at a pair of crossed legs that look a lot like mine, then obviously it is at least possible I have mistaken someone else's crossed legs for my own (perhaps the mirror is in a crowded room). But if I believe it because I am aware of the position of my legs ‘from the inside’ – so to speak – then it is hard to see how such a mistake could happen.

Evans concluded from this that the awareness we have of our bodies ‘from the inside’ is actually a kind of self-consciousness. And the self that we are conscious of is not something immaterial, as Descartes would have it, but a flesh and blood, embodied human being. When I feel that my knees are bent or when I feel myself moving my arms, I am aware of myself. I am not merely experiencing myself as an object, as I would be if I were watching a home movie or if I were looking at my image in a mirror. I am aware of myself as subject. The upshot is that Hume was too quick to deny that the self can be found in introspective awareness. Hume was looking in the wrong place: he was looking for an immaterial subject distinct from our thoughts and experiences. If we allow that the self is something material – something with both psychological and physical features – then we find that the self is observable after all.

But is this kind of bodily self-awareness really immune to error through misidentification? As it happens, when I believe that my legs are crossed because I feel that they are crossed (I don't just see a pair of crossed legs in a mirror), I don't worry about whether those legs are really mine. Or if I believe that I am sitting at my desk because I see my desk in front of me, I don't worry whether it is really me who is sitting there. We perceive the world around us from the perspective of our own bodies; it is our own bodies that we experience ‘from the inside’. But must it be that way? In the 1999 dark comedy Being John Malkovich, an unemployed puppeteer named Craig discovers a portal into John Malkovich's mind. By entering the portal, Craig could experience Malkovich's body from the inside. For fifteen minutes Craig could see the world from Malkovich's point of view, and even control his body to some degree. (After fifteen minutes, Craig is dumped unceremoniously on the side of the New Jersey Turnpike.) Now obviously there are no such portals in the real world. But it seems at least conceivable. After all, we can follow the plot of the movie and imagine what it would be like if the story were true.

In Being John Malkovich there is a single portal, connected to a single man. But what if there were portals everywhere, connected to people all over the world? By stepping through one, you would suddenly experience things from another point of view: you might see a bustling market in Buenos Aires or a crowded urban street in Tokyo. Each time you would experience a new body ‘from the inside’. You could even initiate and control the movements of these other bodies, as easily as you normally control your own movements. Imagine, too, that on such occasions the takeover of the other body is complete. (Here we depart somewhat from the plot of the movie, where Malkovich and Craig engage in a slapstick psychic struggle over the control of Malkovich's body.) And, finally, let's suppose that these portals are inconspicuous, so you can accidentally fall through one without realizing it. One minute you're navigating the streets of Rome, the next you're sitting behind a desk in a cramped office cubicle. Let's call this the ubiquitous portal scenario.

Here it might seem that it would make sense for you to ask, ‘Someone is sitting behind a desk, but is it me who is sitting behind a desk?’ You could answer these questions by looking carefully at your surroundings, or by checking a mirror, or by looking for distinctive birthmarks or jewellery. (Perhaps, after a while, we would all make things easier for ourselves by tattooing our names on the back of our hands!) But here's the point: even when you do conclude that it is you and not someone else, you have done so by looking for distinctive identifying features. That is, you have identified someone as yourself in much the same way that you identify other things and people. And this means that it is at least possible to mistake someone else for yourself. Maybe when the streets of Rome suddenly give way to familiar cubicle walls you momentarily think the person behind the desk is you, and only later – after checking more carefully – discover that it's actually one of your co-workers.

To the extent that the ubiquitous portal scenario is conceivable, it is tempting to conclude that Evans was wrong to claim that judgements about our bodies are immune to error through misidentification. We might conclude that self-consciousness is not, in fact, consciousness of oneself as an embodied human being. The scenario suggests instead that we are immaterial subjects that merely inhabit our bodies. As it happens, we are lodged in a single body over the course of our lives – a body that deteriorates over time, but a single body nonetheless. But that's just because we happen to live in a world without ubiquitous portals. Because we assume that we will not suddenly find ourselves in someone else's body, we feel confident that we will not mistake ourselves for someone else. While we may occasionally find ourselves in situations like that of the Sussex probationary officer, when we are aware of ourselves in the ordinary, and more intimate way – from the inside – we need not worry about mistakes of identification. But this is not because such mistakes are impossible; it's just that they are extremely far-fetched and improbable. We don't worry about being suddenly crushed by elephants falling from the sky. It's not impossible that such a misfortune could befall us, but it's so unlikely it would be pathological to worry about it too much.

But is the ubiquitous portal scenario as coherent as it might seem on the surface? Let's return to Being John Malkovich. Craig has just stepped through the portal. What makes us say, to begin with, that it is Craig who is now being John Malkovich? Why say that the person in Malkovich's head is Craig, as opposed to his co-worker Maxine, his wife Lotte, or his nemesis Lester? Because Malkovich now has Craig's personality, his desires, his neuroses. Because we hear a voiceover of Craig’s inner monologue as Malkovich potters around his Park Avenue apartment. But what makes these desires, these neuroses, this voice, Craig's? Well, they have been associated until now with Craig's body. And the same goes for Malkovich. Why do we say that Craig is being John Malkovich, as opposed to Charlie Sheen? Because Craig is inhabiting a body that we have until now associated with a single actor. As the late Bernard Williams puts the point, ‘it is a necessary condition of making the supposed identification on non-bodily grounds that at some stage identifications should be made on bodily grounds. Hence any claim that bodily considerations can be absolutely omitted from the criteria of personal identity must fail.’Footnote ⁵

Back to the world with ubiquitous portals. You suddenly find yourself in a cubicle. You look around and say to yourself, ‘Rome was fun. Too bad I am back to being me now.’ But in virtue of what would that person be you? You can't say it's because you are inhabiting a body that has until now been associated with a single person. If we are constantly switching bodies every few minutes, we wouldn't come to associate a body with a single person in the first place. Here's my point. We ordinarily talk about individual people in the context of individual people's lives, and our talk of people's lives only makes sense on the assumption that those lives are lived in stable human bodies. I suspect that if the portals were sufficiently ubiquitous, our lives would be so fragmented that our talk of individual people would break down.

Now it would be too quick to conclude that our beliefs about our bodies are therefore immune to error through misidentification. After all, there's room still for the possibility that the portals are just ubiquitous enough that we stumble into them once in a while, but not so often that our lives become too fragmented. Perhaps in such a world there would be room occasionally to mistake oneself for someone else. Nevertheless, the incoherence of the (full on) ubiquitous portal scenario suggests that it's no accident that we are intimately related to our own bodies, and it is this relation that makes us who we are. When I am aware of my body from the inside, I am conscious of myself. And I am conscious of myself as myself, even if it is theoretically possible to mistake myself for someone else.