The person and the glass tunnel

On Derek Parfit, Reasons and Persons and on personal identity
Par David Olivier Whittier

This article was written following the colloquium “Deux siècles d'utilitarisme” held at the University of Rennes 2 in June 2009 and in which I participated.

Read time: 31 min.

Abstract: Personal identity is the idea that each of us is a person, a “mysterious and unique” object, identical over time, the subject of pleasures and pains, thoughts and other qualia, but independent of them. It would even be rational for the good of this object to be the ultimate end of our action.

In this article I argue, drawing in part on the work of the British philosopher Derek Parfit, that this object – personal identity – simply does not exist.

It is on the basis of an erroneous belief that we lock ourselves in a glass tunnel that cuts us off from the rest of the world – both from things and from other sentients. Because of this belief, we are terrified by death. Altruism seems incomprehensible and irrational. Our traditional morals, especially the theories of rights, are built on this mistake; as is our punitive justice system and the sanctification of political rights, contracts and private property. Finally, because of this error, the hard problem of consciousness appears not only hard but desperate.

A critique of personal identity is a necessary condition for moral and political progress. In particular, it sheds new light on the difficult ethical issues that await us in our relations to non-human animals.

Our life appears to us as a glass-walled, one-way tunnel. We have, it appears, direct knowledge of the inner reality of our tunnel, of our “inner world”. Outside the walls lies the “outer world”: another reality the existence of which we acknowledge, because we see it; or rather, because we see part of it and try to guess the rest.

Among the things we see outside, there are other glass tunnels, which we assume to contain other inner worlds each doubly cut off from us as we are from them.

All of this, we accept, is real; but only the world inside our glass tunnel seems real to us outright. It is out of philosophical laziness, perhaps, that we are not solipsists, but solipsism looks quite plausible. All this stuff outside might well be a dream...

The tunnel, over there, ends with our death. The world, we assume, will still exist, but “our world”, the only world that appears certain, will disappear forever. There will be an after, but one that we will not witness. There will be projects, sorrows and joys, but they will not be ours; thus we say of them, “What does it matter to me? For me it will be the end of all!”

We wish it were not so. So we imagine that there will be an “afterlife”, that is, an afterlife of ours – the continuation of the only life that really matters. Thus, the best we can imagine is that our tunnel has no end.


I take this image of a glass tunnel from Derek Parfit. At the beginning of chapter 13 of Reasons and Persons,1 in a clear and expressive passage, he tells us how, when he believed in the reality of personal identity:

✓ (...) I seemed imprisoned in myself. My life seemed like a glass tunnel, through which I was moving faster every year, and at the end of which there was darkness.

But once this notion was challenged:

✓ (...) the walls of my glass tunnel disappeared. I now live in the open air.

Concerning his relationships with others:

✓ (...) Other people are closer. I am less concerned about the rest of my own life, and more concerned about the lives of others.

Concerning his death:

✓ Instead of saying, “I shall be dead”, I should say, “There will be no future experiences that will be related, in certain ways, to these present experiences”. Because it reminds me what this fact involves, this redescription makes this fact less depressing.

These profound changes in Parfit's attitude towards the most intimate issues that we each face – those of life and death – result simply from his having grasped a factual truth. This truth concerns the nature of our being, and, I would say, more generally that of sentient beings. Parfit had grasped that there is no such thing as personal identity; or, to use his preferred formulation:3 that the personal identity that results from our physical and psychological continuity reduces to these continuity relations; it is not a further fact. Parfit thus claims to be a reductionist in matter of personal identity, in contrast with non-reductionists, whom I will also call “personalists” following a text I quote below.

Personal identity is the numerical identity of the person, or subject, between different moments over time. This issue is in fact that of the existence itself of the subject: for if each moment of sentience was perceived by a new, different subject, this new subject would have no identity past the moment of sentience and would not exist in any meaningful sense.

Reasons and Persons is meticulous in its reasoning and often arduous by its analytical style. Despite this, certain assumptions are not always made explicit, such as the identification made at the outset of rational choice with the rational pursuit of the interests of the individual alone. Others are based simply on the author's intuitions.4 A reader who does not share these may be left stranded. This is the case in particular of the “Repugnant Conclusion”,5 which leads Parfit to reject utilitarianism itself; to the reader who does not find it this conclusion repugnant, some of the developments in the last part of the book devoted to the search for a more impersonal ethics may seem less relevant. On the other hand, the question of personal identity is probably too close to our deep feelings for us to ignore the intuitions we have concerning it. The Parfitian method consists in taking these seriously, as factual assertions, and to confront them with thought experiments, with the facts of neurology and the demands of logic. This allows his critique to reach our innermost self-evidence, which appeared to be expressible only through tautologies (“I am who I am”).

Parfit is not the first to have questioned personal identity. In part, his conclusions are similar to those of Locke and Hume, to whom he refers. He tells us that the evidence of the Cartesian “ego” was challenged by Georg Christoph Lichtenberg:

✓ Lichtenberg claimed that, in what he thought to be most certain, Descartes went astray. He should not have claimed that a thinker must be a separately existing entity. His famous Cogito did not justify this belief. He should not have claimed, “I think, therefore I am”. [He] could have claimed instead, “It is thought: thinking is going on”. Or he could have claimed: “This is a thought, therefore at least one thought is being thought”.6

Thus it appears that on the subject of personal identity there was an important debate during the seventeenth and eighteenth centuries, one now largely forgotten. Utilitarianism, which was formalized at that time, would seem the natural place for a critique of personal identity, because it assigns to each moral agent the same goal, that of maximising the collective good, and because this good is defined on the basis of an impersonal aggregation of subjective truths. Paradoxically, it is today mainly its opponents who criticise utilitarianism for its impersonal character and for viewing individuals as mere “containers” for sensations, as Tom Regan puts it,7 despite utilitarians having largely abandoned the task of challenging personalism. I will return to R.M. Hare's Universal prescriptivism, which is based on a personalist assumption, as is the following view expressed by Henry Sidgwick:

✓ It would be contrary to Common Sense to deny that the distinction between any one individual and any other is real and fundamental, and that consequently “I” am concerned with the quality of my existence as an individual in a sense, fundamentally important, in which I am not concerned with the quality of the existence of other individuals: and this being so, I do not see how it can be proved that this distinction is not to be taken as fundamental in determining the ultimate end of rational action for an individual. (...) [A man] may still hold that his own happiness is an end which it is irrational for him to sacrifice to any other; and that therefore a harmony between the maxim of Prudence and the maxim of Rational Benevolence must be somehow demonstrated, if morality is to be made completely rational. This latter view (...) is that which I myself hold.8

Reasons and Persons deals with important topics other than that of personal identity, which forms, however, its core will be my focus here. It appears that Parfit's great merit is to have set the debate from the fundamentally ethical viewpoint of what matters.9 For beyond the descriptive discourse about the existence or not of a certain entity persisting through time, namely the “I”, it is the realm of the prescriptive that forms the crux of the matter. Despite Parfit's deep admiration for Sidgwick,10 his position is opposite to that stated in the above passage. If Sidgwick is wrong and personal identity is not “real and fundamental”, it is not what matters, and it is on the basis of a false belief that we are concerned with the quality of our existence in a manner radically unlike that with which we are concerned with the quality of the existences of others. It is on the basis of a false belief that we are so afraid of death. It is on the basis of a false belief that we view prudence as unproblematic and rationally founded, while despairing of finding any basis for ethics other than our own best interests. It is also on the basis of a false belief that we give a central place in ethics to personalist notions such as rights, distributive justice, reward and punishment, etc.


The term “reductionism” by which Parfit qualifies his views of personal identity can appear to suggest a petty desire to deny what is great. However, one can be a reductionist of various things; we are generally, for example, reductionists of Santa Claus, believing that the appearance of gifts in children's shoes can be reduced to more mundane causes. There is no reductionism “in general”; each reductionism is to be judged on its own merits.

Parfit's use of the term may reflect a desire to maintain a distinction between his thesis and the outright denial of the existence of a personal identity; that is, between the assertion that X reduces to Y, and the assertion that X simply does not exist, the phenomena attributed to X being instead due to Y. This distinction, however, seems to be justified only if one seeks to preserve, in the former assertion, the idea that X can nevertheless be more than Y, that is, can be seen as an “emergent phenomenon”; otherwise, X is only a shorter name for the fact(s) Y that underlie X. But Parfit does tell us that personal identity is nothing more than the facts of physical and psychological continuity. The distinction between reduction and assertion of non-existence has therefore little justification; Parfit's thesis is, in essence, that of the non-existence of personal identity, and contrasts with the opposite thesis: that of the existence of personal identity, as an entity irreducible to relations of physical and psychological continuity.

It is essential to separate the issue of personal identity, that is, the issue of the subject, from that of sentience or subjectivity. Parfit's position indeed challenges the apparently self-evident notion that there can be no subjectivity without a subject. This distinction is relevant because there also exists a reductionism of sentience, and many of the arguments that claim to show the non-existence of sentience, for example those of Daniel Dennett,11 are in fact valid only against the existence of the subject. Instead, Parfit's reductionism, far from attempting to deny sentience, allows us to understand the sentience events (qualia) as existing in the world, rather than as “private” entities existing only from the point of view of a subject.


Because the non-reductionist thesis can be perceived as a mere expression of common sense and is rarely spelled out, I will quote a particularly explicit statement of it:

✓ At the heart of Pope John Paul II's personalism (his philosophy of the person) is the recognition that it is the concrete individual person who is the subject of consciousness. (...) That subject may exist prior to consciousness (as in the case of the human embryo) or during lapses of consciousness (as in sleep or in a coma). But the existing subject is not to be identified with consciousness itself, which is an operation or activity of the subject.12

This subject is a very specific kind of object, of a “mysterious and unique” nature according to the Catechism of the Catholic Church:

✓ In the kingdom, the mysterious and unique character of each person marked with God's name will shine forth in splendor. “To him who conquers . . . I will give a white stone, with a new name written on the stone which no one knows except him who receives it.” (Rev 2:17).13

Parfit, instead, takes a physicalist perspective, one that views sentience as something that happens in our brains, and his book ends with a call for the development of an atheistic ethic:

✓ Belief in God, or in many gods, prevented the free development of moral reasoning. Disbelief in God, openly admitted by a majority, is a recent event, not yet completed. Because this event is so recent, Non-Religious Ethics is at a very early stage.14

Yet it is among the self-described rationalists that one finds some of the most virulent personalist proclamations, in which rationalism and materialism are viewed as disqualifying ethics and “therefore” as justifying the motto “every man for himself” against a background of exaltation of the individual and of His heroic autonomy.15 Without going to such extremes, even the irreligious among us readily subscribe to the Sidgwickian belief in a “self” that separates us, in a fundamental sense, from any other “self”. The task of criticizing this conception appears to me to be one of the founding stones of a non-religious ethic.

Continuity relations

Our personal identity, one might think, is just the identity of our body over time. This latter identity, however, does not hold true, and, more importantly, is not really what makes up our belief in personal identity.

It is true that we are identified with our bodies in our daily interactions. This identification is operationally possible because each body describes a continuous spatial trajectory over time, which in theory allows it to be tracked moment after moment and thus unambiguously assigned an invariant identity.

The material composition of our body changes over time, but again only progressively. Between two close instants, this composition having changed little, we find negligible the error committed in affirming that it is the same material body. However, after a few years our matter is almost entirely replaced. Can we then say that it is the same body, in the material sense?

This question has puzzled philosophers at least since classical antiquity:

✓ The ship wherein Theseus and the youth of Athens returned had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question as to things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.16

Starting from a vessel A, we obtain, by successive replacement of all its parts, a vessel B of which, if it had been built directly from these new parts, it would have occurred to no one that it was the same vessel as A. But the truth value of the proposition A = B depends on what A and B are, not on any intermediate states. This value must therefore be the same, whether B was created by gradually replacing the parts of A or by directly assembling these same new parts. Since in the latter case we would not say that A = B, we cannot say so in the former. The same applies to our body: if after a certain time all its molecules have been replaced, we cannot say that it is the same body.

Above all, physical continuity does not account for what we really view as our identity. Indeed, whether or not we believe in a heaven, we attach a meaning, true or false but intelligible, to the idea of going there. We thus believe that there is an object, “I”, that is logically, if not factually, able to exist without our bodies. And what matters to us is the fate of this object: it matters to each of us whether this “I” will go to heaven or not, not whether our body will go there. Our identity, this object whose future we care so much about, and in a way typically so different from the way we care about the future of others, is not made up of our physical continuity, which only serves to identify it in everyday life.

This “I” is psychological. According to John Locke, personal identity is defined by memory:

✓ For as far as any intelligent being CAN repeat the idea of any past action with the same consciousness it had of it at first, and with the same consciousness it has of any present action; so far it is the same personal self.17

Parfit adds to this criterion other psychological continuities, such as the relation between the intention to perform an act and its subsequent execution. But he also notes that these relations must be completed by transitivity: we rarely remember a distant past day, but every day we remember (much of) our experiences of the previous day. The identity relation is considered established if there exists such a chain of memories from one day to the next.18

Parfit seems to accept that personal identities may validly be defined on the basis of such continuity relations, while arguing that these identities are not what matters. I find it preferable to say that such personal identities simply cannot exist. Indeed, continuity relations, whether they be about the trajectory of bodies in space, their material composition or our memories, always suffer from the same defect: they make the identity A = B depend not on what A and B are, but on the states that link them.

However, because these continuity relations almost always coincide with the idea we have of our identity, it is difficult to bring out in what way we tend so generally to be non-reductionist. Parfit turns to thought experiments in which this coincidence is broken.


The concept of teleportation, as it appears in science fiction and is taken up by Parfit,19 involves the transfer not of the matter of our body, but of information about its instantaneous physical state. On Earth, the traveller enters a cabin and presses a button. A “scanner” then records the position and state of every molecule in her body, brain included, and beams this information to another cabin on Mars, where it serves to create an identical copy out of locally available matter. The scanner also destroys the original body.20 The copy has all the same memories of the original body, will carry out all its projects and perceives itself as the same person.

Two different descriptions of the process are possible. The first is that, rather than being destroyed, the traveller has simply travelled from Earth to Mars. The second involves instead both the death on Earth of the original and the creation on Mars of a copy that mistakenly believes itself to be the original. The criterion of physical continuity is broken, and if psychological continuity is maintained, it is not by the usual means. Memories, for example, are transmitted from the original to the copy by a causal chain involving the scanner, radio waves and the apparatus on Mars. If we accept such a causal chain as capable of representing the continuity that founds personal identity, why should we not accept similarly another causal chain, the one that occurs when we tell our memories to others, and which passes through sound waves and so on? Where do we draw the line? It seems impossible in these circumstances to decide whether personal identity, defined by this continuity, is maintained or not.

The question that Parfit asks is whether the traveller, just before she presses “go”, is justified in believing that she is about to die – and may rightly entertain the corresponding dark thoughts – or merely about to travel. Neither from an exterior point of view nor from an inside one is there any difference between teleportation and travel. I leave in the morning for Mars, and return in the evening by the same means. I – or the copy of my copy – have as vivid a memory of my breakfast on Earth as I do of the afternoon on Mars and the return journey in the evening. The copy of my copy will testify that everything went well; and who could contradict it, or ever could have? Parfit suggests that the repetition and trivialisation of the experience might even lead us to leave aside our initial fears. Would we be right to do so?

We have here a special kind of issue, the status of which it is important to consider. It is not a question of what is (a descriptive issue), nor of what we should do (a prescriptive issue), but of what can found our being sad or happy in advance. Anticipatory fear or pleasure may, of course, serve us when they prompt us to act; but the issue here is about those feelings in the absence of such utility. It is primarily this domain, which I will call that of anticipatory sympathy, that is covered by the Parfitian question of what matters: am I justified, when I press the teleport button, in feeling sad about my imminent death or instead in looking forward to the beautiful afternoon that “I” will spend on Mars?

We may question to what extent anticipatory sympathy is accessible to reason and to matters of fact. We could say that no argument about whether I should or not experience it can touch it, because it is not a matter of duty. If I am going to be tortured tomorrow, should I feel dread? One may expect that I will; but if, while fully aware of what will occur, I remain joyful, so much the better! Why add present suffering to tomorrow's? To what extent, can one then ask, as Parfit does, whether I am justified in rejoicing, or in being sad, when I enter the teleporter's cabin? Can we do more than simply record whatever emotions I happen to feel?

Such a conclusion would be mistaken, and Parfit's question is justified. In one respect, anticipatory sympathy is not immune to reason and matters of fact. If I am unhappy because I believe that tomorrow something will happen to me that in fact will not happen, I am wrongly unhappy. It is not that my emotions should be urged to change: it is that they will in fact change. Whether my fear of flying tomorrow is rational or not, or undecidably rational, it will not persist if I come to know that actually tomorrow I will not fly. If it persists even though I have learned a truth that deprives it of its factual foundation, it can only be because I have not managed to convince myself intimately of this truth (to “realise” it).

Anticipatory sympathy is thus accessible to the cognitive. The cognitive in turn is accessible to reason: reason can allow me to determine the facts.

If I dread one situation, but happily anticipate another, there must be some difference between these situations, a difference that is substantial, that is, is not only about how the situations are described. Parfit shows that in the case of teleportation, as in other cases he examines, it is possible to make an impersonal description of all that happens, including all subjective facts. Teleportation can be described as follows:

— in the departure cabin, it is thought: “I am on Earth and will press the button.”;

— then it is thought, on Mars: “I am on Mars and believe I remember pressing the button.”.

Such a description is complete (describes the facts both materially and subjectively), and yet says nothing about whether the person on Mars is, or is not, the original traveller. Hence there is no substantial difference between the following two descriptions:

(1) The traveller is killed, and a new sentient being, qualitatively but not numerically identical, is created on Mars.

(2) The traveller travels to Mars.

If there is no substantial difference between (1) and (2), then personal identity cannot be what matters. If I have intimately integrated the reasoning that leads to this conclusion, my anticipatory sympathy cannot be saddened by (1) while rejoicing at (2).


Parfit describes several other thought experiments, some of which are not far from being technically possible today, in which a description in terms of personal identity is either impossible or arbitrary, while an impersonal description, which records the existing mental states and locates them in a specific body but does not assign them to a subject persisting over time, is possible and complete. One example is the split-brain experiments, which give rise to two streams of consciousness.21 Parfit imagines a division that may be reversed at will. The subjective description prior to the division – one stream of consciousness –, during the time of division – two streams, each possessing the memories of the previous single stream – and after the reunification – one stream again, which possesses the memories of the original stream and of each of the two separate streams – is not problematic, whereas it would be hard to say which of the two streams, during the time of division, “is really” the original person.

The tunnels disappear

We have seen that the descriptions (1) and (2) above are, in substance, identical. Let us see what makes (1) identical to (2), but different from the following proposition:

(3) The traveller is killed, and no copy is created.

The answer is: the difference is the creation of a copy. Thus, if I am in the position of the traveller who is about to press the button, what is about to happen far away concerns me, as if it were to happen to me; despite it being insubstantial whether it will happen to me or not. It is insubstantial to say whether it will happen in my inner world, or in the world of others. In short: what happens elsewhere in the world concerns me, in the same way as concerns me as what happens “to me”. There is not on the one hand an inner world, which necessarily concerns me, and on the other hand an outer world, which only concerns me if I choose to care about it. My glass tunnel is but an illusion. The soft solipsism that marks the personalist attitude is not defensible.

It is the knowledge of this fact that produced the effects described by Parfit in the following passage quoted above:

✓ Instead of saying, “I shall be dead”, I should say, “There will be no future experiences that will be related, in certain ways, to these present experiences”. Because it reminds me what this fact involves, this redescription makes this fact less depressing.

If the “I” does not exist, and we are intimately convinced of this fact, it is impossible for us to fear its disappearance. We understand that there is indeed an afterlife: that of others, which is as our own and just as real.

Yet Parfit says only that death depresses him less. He wonders whether it is possible for us to really believe in reductionism:

✓ Nagel once claimed that, even if the Reductionist View is true, it is psychologically impossible for us to believe this. I shall therefore briefly review my arguments given above. I shall then ask whether I can honestly claim to believe my conclusions. If I can, I shall assume that I am not unique. There would be at least some other people who can believe the truth.22

His answer is mixed:

✓ I suspect that reviewing my arguments would never wholly remove my doubts. At the reflective or intellectual level, I would remain convinced that the Reductionist View is true. But at some lower level I would still be inclined to believe that there must always be a real difference between some future person's being me, and his being someone else. Something similar is true when I look through a window at the top of a sky-scraper. I know that I am in no danger. But, looking down from this dizzying height, I am afraid. I would have a similar irrational fear if I was about to press the [teleporter] button.


✓ It is hard to believe that personal identity is not what matters. If tomorrow someone will be in agony, it is hard to believe that it could be an empty question whether this agony will be felt by me. And it is hard to belive that, if I am about to lose consciousness, there might be no answer to the question “Am I about to die?”.23

However, even a partial belief in an idea can have practical force. I may never quite believe, when I see a plane on the ground, that such an object can fly, but that does not keep me from boarding it. Just like Parfit, I find the reductionist view “hard to believe” completely, but pondering it and the supporting arguments powerfully helps me to fear death less and to feel closer to others.


Parfit tells us that the walls of his glass tunnel have disappeared and that he now lives out in the open. The exclusive relationship that personal identity used to form “between me and me” – between successive moments of my existence – cut me off from others and from the physical world itself. In reality, the relationship of myself to myself is always of the same nature as that of myself to others. It is physical causality that ensures the structural continuity of our body and brain. It is this same physical causality that could, in a teleporter, ensure the structural continuity between the original and the copy. It is again physical causality that links our experiences and ideas to those of others, when we tell them about them. The epistemological cut-off between the observer and the external world is an illusion: the relationship of me to me, as well as that of me to others, passes through the world. Our own survival depends on its laws. If I really abolished all confidence in the world – as Cartesian radical doubt claims to do – I could not believe that I will myself exist even a second in the future.

Further consequences

The consequences of the critique of personal identity are many and profound. I will consider a few.

The relationship of me-in-the-present to me-in-the-future is of the same nature as that of me to others. The foundational problem of ethics is no greater than that of prudence; or, put differently, prudence is no less problematic than ethics. We can no longer say that our future fate must logically concern us simply because it is ours. Prudence is as difficult to justify as is ethics, and for the same reasons; it is no longer possible to make it a separate domain. The result is a situation of aporia: I appear to have no valid reason to do anything at all, since any act can only benefit a future being, which is not me-in-the-present. This aporia is, I think, fruitful, forcing us to redefine our relationship to the world.24


For a more developed argument in favour of this “broader sense” of ethics, see my “The Subjective Is Objective”, part 4, section “Ethics as a theory of the correct answer...”.

Prudence and ethics merge into a unique domain: that of the prescriptive, or of ethics in the broader sense. This is already implied by classical, hedonistic utilitarianism, which commands us to maximise the pleasure of the world, including our own. Recklessness can be viewed as morally reprehensible, for the same reason as harm inflicted on others.25 Conversely, one can conclude that ethics should be “demoralised”: harm to others is, like recklessness, a mistake, one that stems from the fact that, prisoners of our glass tunnel, we do not grasp how fully real the pleasures and pains of others are.

While classical utilitarianism is impersonal, more modern versions such as R.M. Hare's universal prescriptivism26 and Peter Singer's preference utilitarianism27 tend to reintroduce a large measure of personalism. I view this trend as untenable, at least at the critical level.28 I will sketch out the reason for this by taking the example of Hare. Universal prescriptivism does express moral duties in impersonal terms, but is characterised by the upholding of an essential residue of arbitrariness in the individual's determination of his or her own good:

✓ Some preferences, even in the prudential sphere, may be more rational than others (...); but there remains an irreducible and large minimum of sheer autonomous preferences which rational thinking can only accept for what they are, or will be.29

Self-regarding preference can only concern one's future self; if the relation of me-in-the-present to me-in-the-future is of the same nature as that of another-in-the-present to me-in-the-future, The privilege that Hare attributes to me-in-the-present over another-in-the-present to determine arbitrarily preferences concerning me-in-the-future is unjustifiable. If a residue of arbitrariness is to remain, it should allow everyone to arbitrarily choose everyone's preferences; but then we would have a multiplicity of arbitrary deciders for each preference, which is absurd. This residue of arbitrariness cannot therefore be.

If ethical propositions no longer contain arbitrary ingredients, they may have a truth value. The critique of personal identity thus favours ethical realism, which holds that ethical truths are, in a certain sense, part of the world. It also leads us to view sentience itself as part of the world. As long as subjective experience was conceived as inherently attached to a subject, it existed for that subject only: it was deemed “private”. Whoever took my pleasures and pains into account did so through a heroic act of faith, or in hope of reciprocity. The critique of personal identity leads us instead to view others' experiences as existing in the world in their own right just as our own future experiences. Such sentience realism thus appears as a necessary condition for solving the “hard problem of consciousness” (as David Chalmers has called it), that is, the problem of the very existence of sentience within the physical world. This contrasts with the subject, “mysterious and unique”, which is perceived neither subjectively nor objectively, hence is outside the world. As long as the existence of subjectivity is tied to the existence of the subject, the “hard problem” is in fact a hopeless problem.

By making us take sentience seriously, the critique of personal identity leads us to take seriously any sentience, however different it may be from our own; and to do so as if it were our own, equally with our own. On the other hand, the notion of equality, as it is formulated in the humans-only framework, is mostly relative to the person, in a non-reductionist sense. We speak of the equal value or dignity of persons. Death is then an absolute evil, since it is the destruction of the person; homicide is the ultimate crime. In contrast, since in this framework non-human animals are not viewed as persons – they “live only in the moment” – their lives are almost worthless, have less worth, for example, than the pleasure we take in eating their bodies. The notion of animal equality thus appears to me impossible to formulate in a personalistic framework; for the immediate answer will always be: the life of a fly cannot be worth that of a human.

Utilitarianism, which advocates equality not in terms of an equal value of persons, but in terms of the equal value to give their interests, allows for a clear advance in this area. However, the version proposed by Peter Singer following Hare, preference utilitarianism, reintroduces the notion of the person,30 and makes it difficult to take serious account of the vast majority of sentient beings. It appears instead that only by freeing ourselves from the notion of personhood, through the critique of personal identity, can we arrive at a consistent ethical vision, at least at the critical level, that can take into consideration all sentient beings beyond the boundaries of our species.

This critique has many other political and economic consequences, in particular in relation to private property, the notions of contract, moral desert, etc. It lessens the importance of other notions of identity, such as national identity. It has the potential to bring about profound changes in the whole of our thinking, in our vision of ourselves, in our individual and collective inter-human relations, in our relations with other sentients and in our understanding of our position in the world.

1. Parfit D., Reasons and Persons, Oxford Paperbacks, 1984, p. 281. Page references are by default to this work.

(2. Note irrelevant to this English translation.)

3. For example, page 209 and following.

4. See page 447, where this fact is discussed.

5. This “Repugnant Conclusion” (p. 381 ff.) follows from the imperative of maximising the total utility of sentient beings. To a situation in which a given number of people enjoy a life of pure ecstasy we should, according to this imperative, prefer one in which all lives are just “barely worth living”, provided that the number of the latter lives compensates for the low utility of each. Since this conclusion is repugnant, according to him, Parfit rejects the “total” view of utilitarianism; for other reasons, he also rejects the “average” view.

6. P. 224: This is a partial quote from Lichtenberg C.G., Schriften und Briefe, Sudelbuch K (1794?).

7. Regan T., “The Case for Animal Rights”, from In Defense of Animals, ed. Peter Singer, 1985 (article not to be confused with the book by the same author, The Case for Animal Rights).

8. Sidgwick H., The Methods of Ethics, 1874, p. 498, quoted in part by Parfit, p. 138.

9. See in particular ch. 12, “Why Our Identity Is Not What Matters”.

10. See the introduction by Parfit D. to On What Matters, book in preparation, version 4/2008 available on the web at

11. Dennett D., Consciousness Explained, Little, Brown and Co., 1991. See in particular his critique of the “Cartesian Theatre” in Chapter 5.

12. Donald DeMarco, “Peter Singer: Architect of the Culture of Death”, originally found at, now available here.

13. Catechism of the Catholic Church, §2159.

14. P. 454.

15. An example is the novelist Ayn Rand and the ultra-liberal “objectivist” current she founded. Also come to mind the anarchist Max Stirner, or the justifications of egoism that claim to be based on Darwinism.

16. Plutarch, Life of Theseus, translation A. H. Clough, on Project Gutenberg.

17. Locke J., Essay Concerning Human Understanding (1690), book II, ch. XXVII, sect. 10, on Project Gutenberg.

18. P. 205.

19. P. 199 ff.

20. Such teleportation seems possible in the present state of our theoretical knowledge. On the other hand, conservative teleportation, which Parfit also considers and in which the original is not destroyed contradicts the known laws of quantum mechanics.

21. P. 245 ff. The cutting of the corpus callosum, which connects the two hemispheres, has been practiced for therapeutic reasons and appears to give rise to two streams of sentience.

22. Sect. 94 (p. 274), “Is the True View Believable?”.

23. P. 279 and 280.

24. See my “The Subjective Is Objective”, translated from “Le subjectif est objectif”, originally published in Les Cahiers antispécistes n°23, December 2003.

25. See p. 318, section 106. Parfit's formulation is more nuanced.

26. See Hare R.M., Moral Thinking: Its Levels, Method and Point, Clarendon Press, Oxford, 1981.

27. Singer P., Questions d'éthique pratique, Paris, Bayard, 1997.

28. On the distinction between critical and intuitive ethical levels, see Hare R.M., pp. 25 ff.

29. Hare R.M., p. 226.

30. See Singer P., ch. 4.