Towards a Scientific Theory of Persons

Paradigm Shift

I do not expect a theory of personhood to match all our pre-reflective philosophical intuitions, even if deeply considered and strongly felt (especially if strongly felt!) for two reasons: (1) our best intuitions on this subject are demonstrably unreliable, and (2) billions of otherwise sane and competent people hold beliefs about personal identity which are unsupported by empirical evidence, but to which they have strong emotional attachment. These two facts strongly suggest that there is something wrong with what we are naively inclined to believe about our identity. Hence we should not be surprised to find that a satisfactory solution, when it is found, will at first seem counter-intuitive.

Some theories are hard to believe at first, but easier to accept as time goes by and we become habituated to thinking in a new way. To believe that the earth and other planets revolve around the sun was difficult in the sixteenth century, when throughout prior history the earth was taken as a paradigm of what did not move, providing a fixed frame of reference in which all moving things were seen to move. Five centuries later, many people find it easy to look at the evening sky and see the plane of the ecliptic anchored by the visible planets and the sun that has just been eclipsed by the earth’s horizon, see the angle on which they stand relative to that plane, and visualize the rotation of the earth on its axis, under their feet. Allowed time, people are capable of overcoming initial resistance to a counter-intuitive theory, if it explains more than their old theory. Although some say that the true theory of persons is psychologically impossible to believe—literally unbelievable—I have more confidence in human adaptability.

In The Structure of Scientific Revolutions, Thomas Kuhn showed that even when a scientific theory meets stubborn countervailing evidence, the scientific community will not abandon it until someone comes up with a better theory to replace it. Data points, no matter how hard to reconcile with received theory, are treated as insignificant anomalies until a new theory emerges to explain them. Although presented as an account of how change occurs in science, Kuhn’s work reveals a general truth about human psychology: we need a framework of ideas in which to operate. If questions which we cannot answer are raised about our beliefs, we are much more likely to ignore the questions than to abandon the beliefs, unless a better set of beliefs is on offer.

Our beliefs about persons do a lot of heavy lifting. Personal identity is important not only to philosophers, but to the police, and to everybody. Once I spent four days on a jury whose job was to decide whether the accused was the same person who robbed an apartment. (We decided there was reasonable doubt.) When a man finds a love note in his wife’s underwear drawer, he may be greatly relieved to recognize it as one he wrote himself years ago and forgot. We track the identity of our debtors and creditors as carefully as we track the amounts of indebtedness. Persons are the keystone entities of our social and legal interactions. The distinctions we make between persons—“Jim is more reliable than John.” “Jack deserves the Nobel prize for his life work, but Jenny deserves to be locked away forever for her crimes”—are essential for conducting the world’s business. If a theory of personhood does not allow us to make these important distinctions, it will never gain currency.

There is little point in developing a theory of persons that blurs or denies either the real distinctions between individuals or the real similarities that characterize individuals through the different stages of their lives. This is one way in which Open Individualism fails. In boldly cutting the Gordian Knot of the puzzle cases, by asserting that we are all the same person, it ‘solves’ the philosophical problems of personal identity at a cost that is too high. It does not say how we should think about the important differences between persons. It offers no coherent account of moral and legal responsibility, or ownership of property, or desert.  Any such theory, until it repairs those shortcomings, will be compartmentalized—consigned, as religious or spiritual views are often consigned, to a place in our thoughts that has little to do with how we conduct our daily affairs.

The Anomalous Data

Our inconsistent responses to the puzzles of personal identity are evidence that the concept of a person we imbibed with our mothers’ milk is inadequate. All attempts to defend the traditional concept have failed to match the honestly-reported intuitions of intelligent, thoughtful human subjects. And there have been many such attempts. Perhaps some new attempt will succeed. I doubt that it will. The failure of so much ingenious effort to come up with a criterion of personal identity that matches our intuitions is good evidence that future efforts will also fail.

The puzzle cases have a common structure. All involve a transformative event or process, one or more persons who are alive before the event occurs, and one or more survivors. The question is asked whether somebody alive before the event is the same person as somebody who is alive afterwards. The results reveal tensions and inconsistencies in  received views about what persons are. They are negative results—anomalous data points that cast doubt on the received views, but are not in themselves so much as an outline of a replacement view.

In Reasons and Persons, Derek Parfit argues convincingly that a wide array of puzzle cases show much that is wrong with the old paradigm of persons. But it does not offer a new paradigm of what persons are that is sufficiently fully-fleshed to be believed. A reader can be convinced by the arguments of Reasons and Persons, and yet emerge somewhat befuddled as to what persons really are. As a result, old habits of mind reassert themselves when the reader returns to his normal life—which is where the concept of a person does most of its real work.


The puzzle cases can be viewed as a battery of psychological tests. When considered in that light, they move from the domain of philosophy into the domain of science. As psychological tests, they have positive results, revealing how the respondents think. However, those results are still just anomalous data points until placed within the framework of an explanatory theory.

Almost all test subjects who have not been heavily exposed to philosophical theories of personal identity, and most of those who have been, agree in one thing: if they hypothetically place themselves in the situation of the person who is alive before the transformative event, their judgements of personal identity stand or fall with their willingness to extend the emotional attitudes of self-concern to the survivor. Intuitions about personal identity are grounded in a thought-pattern like this: “If I knew I was about to be transformed in this way, I would (or would not) have self-concern for the survivor of the transformation.”

To say that self-concern stands and falls with judgements of personal identity is to say that there is a strong correlation between the two. It is not to say that one determines the other.

Causation: the Neuroscientific Evidence

There is some neuroscientific evidence that, of the two, self-concern is primary—that our emotions determine our judgements of personal identity rather than the other way around. The evidence is not strong enough to establish that emotional responses are always primary.  But it suggests that sometimes, at least, emotional responses determine judgements of personal identity, overriding other cognitive considerations.

If  V.S. Ramachandran’s explanation of Capgras’ Syndrome, described in an earlier post, is correct, then emotion is primary. The emotional response is taken as evidence for the identity judgement, rather than the identity judgement determining the emotional response.

When a Capgras patient sees his mother, he thinks that she is someone else pretending to be his mother.  Ramachandran’s theory is that this mistake about identity is caused by a disruption in the neural pathways between the amygdala, which assesses the emotional significance of sensory input, and the face-recognition area of the fusiform gyrus. Although the patient can see that the woman resembles his mother, he does not experience the emotions he expects to feel in his mother’s presence, and so concludes that she must be an imposter. The symptoms are very specific: the mistaken identity only applies to persons who are close to the Capgras patient, or to a beloved pet, or to the patient himself, seen in a photograph! Only sight is affected; the patient knows his mother when he talks to her on the telephone. Ramachandran used galvanic skin response (GSR) tests to confirm that Capgras patients do not respond emotionally as normal subjects do when they see their mothers.

Ramachandran’s theory of the Capgras cases suggests that the emotional response determines the identity judgement rather than the other way around. Cognitive function is affected only in judgements of identity, and only regarding identity of persons who have strong emotional significance to the patient. The subject takes his own emotional response (or lack of it) as convincing evidence of personal identity (or non-identity). If causation ran in the opposite direction—if the patient’s belief that his mother was someone else produced the lack of emotional response—it would not be explained by neural lesions between the amygdala and the face-recognition areas. And it would fail to explain why the patient recognizes his mother over the telephone.

In a personal identity puzzle case, the subject is asked to imagine himself about to undergo a transformation, which is described in detail, and which has a survivor. Ramachandran’s theory suggests that when the subject’s feelings towards the survivor determine his belief as to whether or not the survivor is himself.

More evidence that emotion determines cognition, where the self is concerned, is found in Cotard’s Syndrome. Cotard’s patients believe that they are dead, or even that they do not exist, a delusion that Ramachandran describes as “notoriously resistant to cognitive correction.”

Ramachandran explains Cotard’s as “an extreme and more general form of Capgras syndrome.” He describes its symptoms as “what we might expect if all or most sensory pathways to the amygdala are totally severed.”  Cotard’s patients do not exhibit normal self-concern. Cotard’s is a rare disorder, often complicated with severe psychotic symptoms, which make it hard to draw definite conclusions. But the evidence is enough to persuade at least one prominent neuroscientist that disruption to the systems that govern emotional response causes Cotard’s patients to believe that they are dead or non-existent. The philosopher Thomas Metzinger has also written a detailed account of Cotard’s in which emotional impairment plays a key role.

Evolution of Beliefs

Natural selection not only explains gross physical features like skin colour (strong pigmentation offering protection against high concentrations of U-V in latitudes near the equator; fair skin providing more efficient production of Vitamin D in regions of weaker sunlight); it also explains psychological characteristics. Obvious examples are appetites: if an animal lacks motivation to breathe, eat, drink and have sex, it is unlikely to reproduce.

We do not usually think of beliefs as inheritable characteristics. We probably do not inherit beliefs in our genetic material in the straightforward way that we inherit blood type or sickle-cell anemia. More likely, we have genetically-determined predispositions in favour of some beliefs and not others. Because of our genetic inheritance, some things are easy for us to believe and other things are hard to believe.

Daniel Dennett, in ­Darwin’s Dangerous Idea, argues persuasively that the principle of natural selection extends far beyond the domain of biology. It applies equally well to things that are passively reproduced, such as cultural artifacts, as to living organisms that actively reproduce themselves. Artifacts like clay pots and smart phones are reproduced in the environment of human culture. When someone invents something, other people who admire it will make or buy copies; and that is how artifacts reproduce. The underlying principle of natural selection—the features that most improve something’s chances of reproduction are the likeliest to survive—determines the shape and function of the artifacts that surround us just as it determines the shape and function of the living species that share our planet.

Like clay pots and smart phones, beliefs and theories are cultural artifacts. Useful beliefs, like the belief that firing clay pots makes them harder and more durable, are likely to catch on, propagating through their natural environment, human minds.

The point about the evolution of beliefs is an example of how philosophy and science can collaborate productively. Philosophy excels at analyzing ideas: ferreting out hidden assumptions, exposing hidden contradictions, sharpening the linguistic tools which science uses to build theories that explain, and improve our ability to predict and control, reality. If what requires explanation is a belief, the role of philosophy is to elucidate the belief—to spell out its meaning and implications, how it fits with the rest of the believer’s theory of the world. The role of science is to explain why organisms like ourselves would have such a belief, and to identify the specific physiological structures that support it.

In an earlier post, I wrote about the evolutionary benefits of the self-model and self-concern. Natural selection favours an organism’s ability to imagine the future in detail, and to imagine itself as part of that future. This ability has evolved to a high level in human beings. It enables us to plan effectively, and achieve our genetically-motivated goals with a much higher success rate than most, possibly all, other animals. It works because our mental images of  ourselves in the future are loaded with emotional affect, and highly motivating.

Elucidation of Beliefs

Science can explain the evolutionary benefits of the beliefs we have, and their functional roles in our psychological and neurological machinery. Philosophy uses thought experiments to expose hidden inconsistencies in our beliefs. Philosophy also elucidates our beliefs, exposing relationships and dependencies that may not be obvious at first glance.

Almost all respondents to the puzzle cases show a strong correlation between judgements of personal identity and self-concern. People do not easily distinguish between the belief that they are a particular person who will be alive in the future, and the emotions of future-directed self-concern. It does not occur to them to make the distinction. But the association is stronger than that. When asked to make the distinction, they say they can’t make sense of it. That is an indicator that the association is necessary; that the notions of personal identity and self-concern are conceptually linked. They cannot be separated without changing the meanings of the words we use to express them.

Philosophy can clarify our beliefs, and show what’s wrong with them. Science can explain why we believe them. If both efforts are successful, we have a firmer place on which to stand to question our beliefs and decide what it would be better to believe instead.

A New Paradigm

If we reject the traditional concept of a person, what are we left with? What should we believe about persons? What are we?

I offer the theory that persons are informational entities as a new paradigm. According to the Informational Theory of Persons, we are attributes. We are not essentially tied to any substance. We are not essentially tied to any physical substance, or object; instead, each of us is instantiated in a physical object, our body. We are not essentially tied to any spiritual substance either, because spiritual substances do not exist.

The way in which we are instantiated in our bodies is similar to ways in which other informational entities are instantiated in physical objects. It is like the way Melville’s novel, Moby Dick, is instantiated in a bound volume in my library. It is like the way Microsoft Word, which I am using to write this post, is instantiated in my computer’s memory.

I sketched this theory of persons in a series of posts ending with What We Are, but left several important philosophical questions unanswered. Instead, I proposed to step back from philosophy and “examine the Information Theory another way, by asking what our lives would be like if we believed it.” To some extent, I was able to deliver. If we come to accept the Information Theory of persons, we will not hesitate to use information-based teleportation as a means of travel, and to regard a backup file as a new and better life insurance. We will feel differently about ourselves and others, about dying, and about the future after our deaths.

Now it is time to return to the unanswered questions, because any paradigm that leaves central questions unanswered will remain hard to believe. One of the most important questions raised in ­What We Are is whether or not what Parfit called The Extreme Claim is true. This is the question whether or not concern for our own future is rationally required.


Dennett, Daniel (1995), Darwin’s Dangerous Idea, Simon and Schuster.

Kuhn, Thomas (1962), The Structure of Scientific Revolutions, University of Chicago Press.

Metzinger, Thomas (2003), Being No One,  Massachusetts Institute of Technology

Parfit, Derek (1984), Reasons and Persons, Oxford University Press.

Ramachandran, V.S. (1998), “Consciousness and body image: lessons from phantom limbs, Capgras syndrome and pain asymbolia,” The Royal Society

Ramachandran, V.S. (2011), The Tell-Tale Brain, W.W. Norton and Company


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One Response to “Towards a Scientific Theory of Persons”

  1. Jesus says:

    Excerpts from ‘On Ego – A Theatre Essay’ by Mick Gordon and Paul Broks, (inspired by the book ‘Into the Silent Land’ by Paul Broks). Oberon Books Ltd. and Soho Theatre, London 2005.

    Ok, I think we should make a start now. And to start with, can I ask you all to please look at me. At my face. This one. What do you see? When you look at my face, what do you see? I’ll tell you what you don’t see. What you don’t see – unless I tell you how to look – what you don’t see are the facts of the matter. You don’t notice, at first, that my face – any face – is really just an animated device attached to the outer surface of a bony box. But that’s what it is. It works this way because just below the surface you have these bands of fibre tugging your tissues this way and that and these fibres are stimulated by electromechanical impulses that shoot down from deep inside the box. There’s also a hinged structure here and when it lowers it opens up a gaping hole. Then you have a protruding construction in the central region, with two vents, and these deep cavities up here on either side. There’s a mobile spherical structure stuffed into each of them. Now this is very odd. If you poke the side of one of these spherical structures – very gently – the whole world wobbles. Round to the side you have these things… Try as you might you won’t actually see them but you can feel them alright – all curly and folded and if you wear glasses, you’ll appreciate that these rather odd structures are perfectly placed to support the arms of your spectacle frames – evidence as good as any for intelligent design. So, what do you see, when you look at my face, if not the bony box and the mechanical things and the cavities and the protruding structures? You see a person. You catch my eye and you see the gleaming signal of consciousness. A person. You imagine some ethereal space beneath the vault of my skull, lit by shifting patterns of feeling and thought, charged with intention. A person. Behind every face – we think – there is a self. An essence, an ego, an ‘I’. The illusion is irresistible. Why so? Well, we see, we hear and we speak through the face and it also displays our feelings, so we have the impression that consciousness – the stuff of self-awareness – is located in the same region. And, of course, where the box goes, you go. It’s undeniable isn’t it: you’re in there somewhere? And if you’re in your box you imagine that other, similar, boxes must also be inhabitated. Well they aren’t. Look at the space behind the face. Now what do you see? The fact is there’s nothing but material substance: flesh and blood, bone and brain. You look down into an open head, watch the brain pulsate, watch the surgeon tug and probe. And you understand with absolute conviction that there’s nothing more to it. There’s no one there. Nobody home. No essence, no ego, no ‘I’. It’s a kind of liberation. (…) Like the surface of the earth, the brain is pretty much mapped. There are no secret compartments inaccessible to the surgeon’s knife or the gaze of the brain scanner. There is nothing you can’t touch or squeeze, weigh and measure, like any other object. There is no ghost in the machine… just a machine. And the machine is awesome. It contains a hundred billion neurons. And each of these neurons is linked to as many as ten thousand others which means there are potentially more possible patterns of connection in your brain than there are atoms in the known universe. Can you imagine? Look close. Shrink yourself down to the size of a brain cell. Enter your own head. Picture yourself perched like a monkey in the jungle of connections. Take a good look around. There’s not a spark of colour or whisper of sound. Where are your feelings and thoughts? Where are your hopes and fears? Your memories? Where are you? The jungle is dark and all is quiet. It’s hard to fathom. Really it is. We want to believe there’s more to us than that. More than just a mass of tiny robotic cells. How can we possibly accept Francis Crick’s ‘Astonishing Hypothesis’? [“… that ‘you’, your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behaviour of neurons. That conscious experience is not caused by the behaviour of neurons, it is the behaviour of neurons”]. So how does meat become mind? When I first held a human brain in the palm of my hand I felt… ambivalent. The fascination! But also a little distaste. I was surprised by how heavy it felt. Perhaps a part of me had expected it to be weightless, like a mental image or a train of thought. We never feel the weight of our own head, do we? It just seems to float there like a thought bubble. It was a dissection class and I wanted to slice this brain apart and look inside. But I felt reluctant to start cutting – Why? Was it a sacrilege? I imagined the worlds bound in this nut-shell. Sun, moon, sky, clouds, people, places, pleasure, pain, knowledge, beauty, right and wrong. Love and loss. Visible and invisible things. An entire universe, an infinite space stuffed inside this kilo and a half of meat. A lump of meat. (…) So how do we get from a brain to this… conscious self-awareness we all seem to float around in? The greatest scientific and philosophical riddle of all: How does the brain construct a self? It’s tempting to go back to our intuitive ego theory –the assumption that within the machine, behind the structure we call a face, there lurks an ego, an essence, and ‘I’. The experiencer or our experiences, working the controls, steering the body through the world. But it is an illusion. Our actions and experiences are not owned by some inner essence. Actions and experiences are all we are! Each life is just a long series or bundle, of interconnected sensations and thoughts. And the mental processes underlying our sense of self – feelings, thoughts, memories – are scattered through different zones of the brain. There is no special point of convergence. No central core. We come together in a work of fiction. Our brain is a story-telling machine. And the ‘self’ is a story. And weather you like it or not, at this very moment yours is being told. (…) But this bundle theory is difficult to accept. Instinctively we demand: If the self is a story then who tells the story of the self? That’s like asking, who thunders the thunder, or rains the rain. It’s not so much a question of us weaving the story as the story weaving us. (…) I, I, I! Always I! I wake up in the morning; I go to work; I feel happy when things go well and I feel frustrated when they don’t; I hold certain beliefs and I express various opinions; I used to like Beethoven but now I prefer Mozart; I like chocolate better than cheesecake; I enjoy walks in the countryside; I take the view that people should be kind to one another, and I feel bad if I do the wrong thing. I act, I feel, I think, I believe, I grow older and I change in other ways. But ‘I’ am always there at the centre of things. But what is this ‘I’? The experiencer of experiences? The thinker of thoughts? The doer of deeds? The simple fact is that there is no ‘I’ beyond the ‘I’ of grammar.

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