Theo Todman's Web Page - Notes Pages
Personal Identity
Thesis - Current Stance
(Work In Progress: output at 18/05/2026 01:16:19)
Introductory / Methodological Comment
- The purpose of this Note is to provide a periodic refocusing of what my thoughts and beliefs about the topic of Personal Identity currently are. Previous versions can be found from the list below.
- This version has links to the various other Notes that expand further on the issues raised and supply extensive reading lists.
- While very often these Notes are of the “promissory” variety, the links will remind me to improve them as needed. The ‘Thesis Text’ of these Notes is embedded in the latest version of my Thesis1.
- The intention has been to include in this paper – in a coherent and readable order – links to ALL the Notes related to the topic of Personal Identity collated in my Personal Identity Notes Jump Table. With one exception – Kant2 – this has been achieved. .
- The main text of this paper forms the main text of the final Chapter of my Thesis in its two (automatically synchronised) forms:-
→ Thesis - Personal Identity – Chapter 12 (Conclusion)3
→ Thesis - Chapter 12 (Conclusion)4
Main Text
- What are we5? This is one of the most important questions we need to ask ourselves. Just what kind of things are we? The question is closely related to a similar one: just what sort of adventures can individuals such as ourselves survive6? This second question sheds light on the first for if there are certain contingencies that we think we would – or would not – survive, when a typical member of that kind would not – or would – survive, then that kind may not represent what we really think we are. Of course, we might be wrong in our estimations, but at least this will raise the question.
- How should we address such questions? We want an inference to the best – or most probable7 – explanation8 of the facts and our intuitions. There’s the Simple View9 that claims that Personal Identity is brute and irreducible10. And there are Hybrid Theories11 that try to combine the most appealing parts of otherwise conflicting views.
- Why is this not a trivial question? If we look at a dog, say, and ask what it is, the answer to such a question is obvious – it’s a dog! It may be our pet – with a name – a particular individual12, but when we ask what kind13 of thing it is, it’s a member of the species canis lupus. So, when we look at ourselves, the obvious answer is that we are human beings14 – specifically human animals15, members of the species homo sapiens16. That is the answer posited by the Animalists17, amongst whose number – broadly speaking – I place myself, who accept the biological view18 of personal identity, that our criteria of identity19 are Biological20.
- If the arguments for Animalism21 are sound, such as that from evolution22, then our persistence criteria23 – the necessary and sufficient conditions for us to continue in existence24 – are the same as those of other animals25 – the great apes, say, under which category we fall, biologically speaking. Why is this not the end of the story? Well, this is because – despite being a species of great ape – human beings are special in that we have enhanced intelligence26 and cognitive capacities. We are morally accountable. In sum, we are persons27 and have a “first person perspective28” (FPP) on the world – something most philosophers deny to other animals – and care about our futures29 and – wantons30 apart – agonise over our past mistakes. Sometimes, other qualifications are added (required of typical – if not all – exemplars, such as Free Will31, Language32 or integration into a Society33, but this list can appear arbitrary, and I doubt that the term ‘person’ is a natural kind34 term with a meaning that can be discovered.
- Lynne Rudder Baker claims this FPP makes an ontological35 difference, rather than being – as I think – a special property of human beings that may or may not be had in particular cases. Baker36 accuses the animalists of not taking persons seriously37. I might just note that there’s a facile and confusing answer to what we are, that is “people”. You may have noticed that I used the technical term “persons” as the plural of “person”. Some philosophers annoyingly use the term “people”, but this confuses the issue. When we say there are ten people in the room, while it is clear in normal circumstances what we mean – dogs don’t count, for instance – but if there happened to be a Klingon and a visiting angel, would they count as people – non-human persons38 – or not? They are – we may suppose – persons, but they are not human persons39
- Since at least the time of Locke40, this fact of our mental41 exceptionalism has tempted philosophers to say that the sort of continuity42 that’s the most important for our identity-preservation is our psychology43, in particular our Memory44 (or quasi-memory45, to avoid circularity); psychological continuity46 rather than our physical continuity47 – historically bodily continuity48 determined by the bodily criterion49 of identity. This psychological view – adopting the psychological criterion50 of identity – still has its supporters – not only for those such as Dean Zimmerman and Richard Swinburne who believe in immaterial souls51 – and therefore adopt the soul criterion52 – but for the many who think that psychological continuity and connectedness53 is constitutive of the identity of persons (though David Lewis’s Methuselah54 TE shows how silly this idea is). It is also implicit in the ideas of the Transhumanists55 who think that – come the Singularity56 – we might be capable of being uploaded57 to computers58 (assuming the truth of Functionalism59) and thereby achieve a state approximating to Immortality60.
- Before proceeding further we have to say something brief and sketchy about identity and persistence61. “Identity” – in the sense of “numerical identity62” – is a relation a thing holds to itself and to nothing else. A is identical to B if A and B are the very same thing. It is an equivalence relation, being reflexive, symmetric and transitive; and, many of the sticking points in the philosophy of personal identity arise from this fact.
- It has nothing to do with “identity” as a sociological concept such as national identity, sexual identity or identification with a particular group.
- Also, John may be said “not to be the same person” since he took heroin, but he is still John and still the same individual; it’s just that his personality63 has changed.
- It also has nothing to do with “narrative identity64” – which is the story we tell about ourselves in an attempt to make sense of our lives – or the group we identify with (such as racial65 identity).
- Finally, it has nothing to do with “exact similarity66”: my television may be “identical” to yours, but that doesn’t mean I can have yours if mine breaks. They are – or were, when manufactured – exactly similar, but are distinct.
- “Persisting” is what a thing does in continuing in existence. As we noted above, there are what are called “persistence conditions” – specific to a kind of thing – that set out what vicissitudes a thing can survive if it is to remain that very same thing. There are sometimes hard cases, and it can seem sometimes that there is an element of convention67: is a particular club still the same clubs after it has lost all its original members, changed its name, and so on? This is particularly the case for Artifacts68, which have other unusual and conventional properties – like surviving as scattered objects69 (think of a watch disassembled for cleaning, or the Ship of Theseus70 prior to reassembly). But we can’t accept that our own existence is a matter of convention, though this could seem the case with the once-dominant psychological view71 (PV) of personal identity: just how much psychological connection could I lose with my former self – philosophers wondered – and still be me? However, things seem simpler and more objective for organisms72, which persist despite exchanging material with the environment and changing many of their properties73, provided they are caught up in a complex and hopefully long drawn-out event (or process) starting with Animation74 and known as a “Life75” and terminating with another process – their Death76 (controversially preceded – in humans – by brain death77 or a Persistent Vegetative State78 and sometimes accompanied by Near Death79 or Out of Body80 Experiences).
- In the above I have assumed at least three things.
- Firstly, that “things” – or at least some things – exist. There’s a philosophical – metaphysical81 – position known as “Process Metaphysics82” (or “Naturalised Metaphysics”) that gives the focus to process rather than ontology, particularly in the case of organisms. I’m not sure how fatal this is to my approach, since I admit that animals are individuated by their lives, which are processes.
- Secondly, that we exist. This would seem hardly worth mentioning, other than that certain philosophers – nihilists83 – have argued that we (whatever we are) or – for similar reasons – various common things like hands – don’t exist.
- Finally, I assume that things do indeed persist, at least some of the time.
- I can’t really address these foundational issues here but will just say a few words on the second issue. There are a lot of interconnected issues to do with the philosophy of time84 and change85, in particular the problem of temporary intrinsics86. How can the leaf that was green yesterday be the same leaf if it is brown today? How can the old bald bloke I87 am today be the same individual as the hirsute teenager all those years ago?
- Some philosophers – the exdurantists88 – say that there’s no relation of identity across time, but merely a weaker counterpart relation analogous to that between an individual and its counterpart in another possible world.
- Others – in particular Derek Parfit89 – have said that even if there is identity across time, it’s not what matters90.
- In what follows, I assume that we exist and that we continue to exist self-identically across time and that this identity relation is important (as is the concept of identity itself, pace the early Wittgenstein91. We could not carry on our lives without these assumptions even if – philosophically-speaking – they were false; but I think they are true: I don’t want to distinguish the “strict and philosophical” from the “loose and popular” senses of identity first raised by Joseph Butler. I also assume the standard logic of identity92 and reject all heretical accounts, such as contingent identity93, indeterminate identity94, partial identity95, relative identity96, and vague identity97, that are invented from time to time as radical solutions to the difficult questions of persistence. In particular, I reject the view – known as occasional identity98 that – while (say) I am not identical to my younger self – yet I was that individual, just not any more. I also accept Leibniz99’s Law – that if A is identical to B then A and B share all their non-intensional properties and the ‘Only X and Y’ Principle100, that in saying whether X is identical to Y, the existence of some other entity Z should have no bearing. I’m suspicious of Haecceity101, where an object can have no essential properties. Bundle Theories102 put the cart before the horse.
- Now back to the main thread. Most Anglophone philosophers these days are naturalists103 and in particular physicalists104 (though maybe most non-philosophers are unreflective dualists105). Physicalists take the view that ‘mere matter106’ can – if suitably organised – think107. Physicalist philosophers have a problem if they have hopes of post-mortem Survival108. If the human organism is totally destroyed – eg. by cremation, explosion, or eating of worms – just how does the very same individual get from this life to the next? Opinions tend to be constrained – even for philosophers – by particular Religious109 creds. Christian Materialists110 have had a go at thinking this through and acknowledge the difficulties. Peter Van Inwagen attempted to show that it is at least logically possible by having God snatch away the dying body immediately pre-mortem, replacing it with a simulacrum. Dean Zimmerman – while himself a dualist – has suggested a “falling elevator” model to help out his materialist friends, whereby there is immanent causation111 (by some unknown natural or supernatural process) between the dying body and the resurrection112 one so that the dying individual escapes in the nick of time to the next world without loss of numerical identity113. Others claim that God’s omnipotence is sufficient and is sovereign even over the laws of logic, so that problems raised by identity being an equivalence relation can be overcome by brute force. Maybe so, but if we ignore the constraints of logical possibility114, we have no way of arguing the matter, so let’s not bother.
- However, most Christian materialists prefer an alternative. Some recognise that getting from here to the next world with temporal or spatial gaps115 raises difficult questions – much as there are for reincarnation116 where there is supposed to be an interregnum117 between one incarnation and the next, presumably involving disembodied existence118 – as to whether the numerical identity of the individual is preserved but adopt an alternative solution – the Constitution View119, which is slightly reminiscent of Aristotelian Hylomorphism120. On this thesis, the person is distinct from the human animal – “just as” the statue121 is distinct from its constituting122 marble – so that the very same person – tagged by the unique “first person perspective” noted above – can be constituted first by its earthly body, and subsequently by its heavenly one.
- Some Animalists have what they think of as a knock-down argument against the Constitution View. Eric Olson calls it the “Thinking Animal123” argument. If the person and the animal are distinct things, albeit co-located, there are too many thinkers – because the animal can certainly think, as can the person, so we have two thinkers where we thought we had one – which is one problem; and there’s another – how do we know which we are, the person or the animal? I’m not impressed by this argument. There are several “multiple occupancy” conundrums – or cases of coincident124 objects – that have been claimed at one time or another to deny the existence of things we are sure do exist. Dion and Theon125, Tib and Tibbles126, the “problem of the many127” and so on. We just need to sort out our rules for counting128. Also, the person my Supervene129 on the animal.
- A minor variant of the above ‘counting’ problem is Multiple Personality Disorder130, where certain holders of the PV claim that there really are multiple persons inhabiting the same body. This raises questions about just how unified a person131 is even in non-pathological132 cases. We might also adduce Dicephalus133 and other cases where the numbers of human animals and human persons don’t quite seem to tie up.
- Also, the whole question of three- versus four-dimensionalism (3D versus 4D; endurantism134 versus perdurantism135; the latter idea popularised by David Lewis136) – whether a persisting thing is wholly present at a time – or whether only a temporal part is present, the thing as a whole being a “space-time worm” – bears on the question of counting. If different things can share stages – say the person and the human animal, or the statue and the clay – then we have to be careful how we count. In the case of a future fission137 – whereby two space-time worms share their past stages but will ultimately diverge – we might not know how many to count at any one time, but this will often not matter for practical purposes.
- There’s also – in a 4D world – the issue of Personites138, temporal parts of perdurant persons. If these exist, then one personite may get the blame for misdemeanours of another.
- I think the idea of a first-person perspective is important. It is this that provides the pull against animalism139 when linked to various thought experiments140 (TEs) that we’ll come on to presently. However, I still don’t like the Constitution View141. My objection is that the FPP is a property of something else – like a smile142 – in this case of a human animal, though the smile might belong to a cat. You can’t take the very same smile from one cat and place it on another (it would be at best an exactly similar smile) – let alone have a disembodied smile like that of the Cheshire Cat. Similarly, you can’t take the very same FPP from one body and plop it onto another. True, it might be a qualitatively exactly similar FPP, but not the same one. What’s to stop that FPP being plopped on several resurrection bodies? Which would be numerically identical to me, given that they can’t all be, in the absence of 4D?
- What are the temptations for not sticking with the animalist approach – which ought these days to be the default position in the absence of anything more compelling? As noted, the apparent lack of rational expectation of an afterlife is one incentive to look elsewhere, so “elsewhere” is a favourite for those who can’t bear the thought of their selves expiring with their bodies143. Of course, not all think an indefinite life a good thing: the Makropulos Case144 is the locus classicus of this controversy and most of us – most of the time – practically speaking act as though we were immortal (see the case of Tolstoy’s Ivan Ilych145). We’ve noted the Christian dualists and materialists, but what about the Transhumanists? There’s the relatively metaphysically uninteresting case of cryoscopy followed by repair and resuscitation; there we have material continuity, and no possibility of reduplication146, though some might claim there is too much outside interference for identity to be preserved. But, what about the “hope” of “you” being uploaded to a computer? There seems to be an idea about that “we” are really software (or even data or information147), when we are clearly material beings. If we are software, it is said, then we might “run” on different hardware. I have two issues with this, apart from the immense technical obstacles to be overcome both in “scanning” the “real you” and providing a computer of sufficient power to run your program and the virtual world for you to experience, Matrix-like.
- Firstly, what sort of thing is a program? It’s an interesting question whether a program has persistence conditions. Is Windows 10 the same program as Windows 0? Whatever the answer to this question is, a program would seem to be a kind of universal148 rather than a particular, and “we” are particulars.
- This leads to the second issue – a reduplication objection. Say we developed a sophisticated program that could run on an open-ended number of exactly similar robots. No two of these would be numerically identical to one another – they would be distinct, though exactly similar. So, were the program to be a simulation of your brain, it could run – presumably – on an open-ended number of computers – and these computers (or computer partitions) would not be identical to one another, so none of them could be you, as you could only be one of them, and there’s no principled way of saying which – there is no Closest Continuer149. The same objection prevents Star Trek-like teletransportation150 – were it possible – being identity-preserving: the individual arriving at the destination is at best a replica151 of the one that set off. I might also add that no “program” is – in itself – conscious152, though a machine that runs it might conceivably be. Mind you, there are arguments against this supposed conceivability as well – originated by John Searle – at least for digital computers. Quantum Mechanics153 may help, as it’s sometimes invoked to ‘explain’ phenomenal consciousness, but this seems to be ‘explaining’ one poorly-understood phenomenon by one even more poorly understood.
- Incidentally, the transhumanists seem to imagine unending computer life as a secular heaven, but it could just as easily be a secular hell. Just imagine being tortured endlessly by some unfeeling software agent that doesn’t know or care what it is doing. I think I’ll give that a miss.
- So, I remain wedded to my view that we are human animals with the persistence conditions of such. “Person” is not a substance154 sortal155, but an honorific that refers to some substance during some periods of its existence when it has the requisite mental and moral properties156 to qualify. “Person” is a Phase Sortal157 (like “teacher”; I’m somewhat indebted to David Wiggins158 here) that – in the case of “person” – applies to most humans most of the time but need not apply to all humans all the time. There are ethical consequences for this view, but they are not as dramatic as is sometimes urged. Non-persons don’t have moral responsibilities, as is already recognised for demented or infant humans, and all non-human animals. The obverse – that persons allegedly have no moral obligations towards non-persons159 – or that non-persons have no rights – is the sticking point, and ought to be reflected in a more humane treatment of all non-persons rather than that we might contemplate sending human non-persons as well as non-human non-persons to the slaughter-house. We might also ask whether being a person is ‘all or nothing’ or whether there can be Degrees of Personhood160; maybe the higher animals are persons of a lesser degree. While this is all a matter of Semantics161, I wouldn’t go so far as some modern philosophers who propose including Plants162 in the scope of moral patients.
- So, what are the problems for animalists163? There are several. Some – like the so-called “corpse problem164” (is my corpse me – only dead – if not, where does it come from? It doesn’t have the persistence conditions of an organism) are probably relatively easy to overcome. Recently, I’ve discovered that animalists – like (but for different reasons) those who think we are essentially165 persons – allegedly have a “fetus problem166”. Animalists – saying that we are essentially animals – have (it seems) to say that we were once foetuses – which appears to be what our animal once was. But was this fetus once a proper part167 of its mother? There’s work currently going on to suggest that this is so – and if so, just when did the new human animal come into existence? However, I don’t think any of this seriously threatens animalism. Maybe things can share parts. Or maybe the ‘container model’ of pregnancy168 is correct, whereby Abortion169 is killing (if not murder) rather than an amputation. Going further back, how do Embryos170 – let alone Zygotes171 – fit in? Just what is ‘our’ Origin172? It is usually taken to be after the possibility of Twinning173 is past (and the existence of ‘identical’ twins shows that we are not identified by our Genome174. Maybe animalists should have considered these problems more than they have, but animals do come into existence sometime – presumably by the time of birth at the latest – and that’s enough for an animalist.
- The real problems for animalism stem from the force of thought experiments such as the “brain transplant175 intuition176”. An animalist seems forced to say that I would not “go with my brain” in the circumstance where my brain is transplanted177 into another body, when it seems to most people that I would. The alleged reason for this is that at least some animalists consider the brain to be “just another organ” that we might lose like we might lose a kidney, provided the animal is kept alive. Doubts about this have led some to think that we are not “really” whole human animals but proper parts thereof, maybe not brains178 as such, but brains and a few other bits. This does seem comical. Just how large am I – would I fit into a hat-box, as Olson179 asks? Animalists are on firmer ground in resisting thought-experiments such as Brain-State Transfers180, where memories and other psychological properties are copied from one brain to another, or Siliconisation181, where parts of the brain are replaced by computer circuits.
- My view is as follows. I am currently (thankfully) a whole human animal. My wife worked in the NHS rehabilitating amputees, and I think it is right to say that they also are whole human animals, though they lack parts that most of us have. No doubt they could lose more parts – and some diabetics sadly do. So, we might view a “brain in a vat182” – one ready for transplant – as a “maximally mutilated” human animal. Maybe – in the case of a brain transplant – a prior animal has fissioned (divided into two) when the brain is extracted and we now have a case of the fusion183 of two animals (the brain from one fusing with the body of the other). It might be argued that our identity-logic isn’t quite up to deciding who is who in such circumstances, but the stakes seem high enough to demand an answer, for which read on.
- I doubt whether the transhumanist hopes of augmenting our physical or mental attributes by effectively converting us into cyborgs184 is much of a threat to animalism. We don’t worry about our spectacles or our mobiles phones making us any less mammalian. Closer integration with AI applications is only the next step for the extended mind. I suppose there might be Sorites185-style Vagueness186 problems in the gradual Metamorphosis187 into an Android188 (or a Chimera189).
- So, is there any purchase in thought experiments that putatively have my first person perspective persisting in cases where there is no identity preservation. Could it be the case that “it seems to me” that I have survived some vicissitude – a cerebrum190 transplant, say – but I am mistaken? Some philosophers argue that this happens every night – I go to sleep191, and when I wake up I just assume that I am identical to the individual who got into bed, but how do I know? I might be intellectually convinced by third parties – those other than the sleeper and the waker – one way or another, but how would this affect how it seems to me? Take the teletranportation case. Because of the reduplication objection (unless we are 4-dimensionalists), we should say that numerical identity is not preserved. The teletransportee is a Clone192. But – if the technology works, and I am the teletransportee – the individual (or 77 duplicates193) would (all) wake up convinced they were me, yet they must be deceived. Thankfully, reduplication is not a problem for whole-brain transplants, but it is for idempotent half-brain transplants, though I think the identity problem there occurs during the fissioning process rather than when the half-brains are implanted. Commissurotomy194 is a more complex case.
- I continue to think that there is a distinction to be made between forward and backward psychological continuity195, though I don’t see how third parties – or even first or second parties – could tell the difference. It makes all the difference to me if I go to sleep and someone else wakes up thinking they are me – as against the normal case where I go to sleep and I wake up. In the former case – for me – there’s just an endless nothingness, of which I know nothing, while in the latter case my experiential life carries on. However, backward psychological continuity – what it feels like looking back – is the same for a survivor and one who only thinks he’s survived.
- In the case of the split-brain transplant, however, how is it all supposed to work, experientially? Neurosurgery is – even today – carried out on substantially conscious patients, as that way there’s a quick feedback loop to tell the surgeon whether he’s destroying any important areas of cognitive function. What would it be like to “fission”? Maybe I lack the imagination, but it seems to me that my First-Person Perspective would go along with whatever was the dominant hemisphere, assuming this “seat of consciousness” is initially located in one hemisphere or the other. If it is not, then it would presumably be destroyed, and two new ones would be created in this miracle operation. Either way, this would sit comfortably with the logic of identity which would not be violated, as at most one of the recipients would be me. I can imagine being ripped apart psychologically, but I can’t imagine going two ways.
- Of course, there are physical and metaphysical issues with the whole idea of brain transplants – the physical structure of the brain196 reflects “its” body, and mental faculties are not fully localised, so it’s not just the immensely complex task of “wiring up” the brain to its new body that presents a challenge. Half-brain transplants are even more problematical as in the TEs the brain stem is not split, but only the cerebra are supposed to be transplanted. It’s not clear to me whether there is pervasive confusion here and that these thought experiments are underspecified to the degree of incoherence. Some philosophers – eg. Kathleen Wilkes – think TEs are unhelpful in the philosophy of personal identity, and that our concepts are not up to being probed in this way. I’m not so sure – the TEs are about us, not our concepts197, but accept that Fictional198 cases can be inadequately described and are therefore unreliable. What Descartes199 thought he could clearly and distinctly conceive of was not always possible. Some consider Time Travel200 to be possible, in which case it would have a bearing on our enquiry. I had some fun with Dracula201, but philosophical Zombies202 are misleading in exploring Consciousness (if physicalism is true, then they are impossible, so assuming them begs the question). Actual cases – such as Clinical Observations203 – are better than invented ones.
- There is finally the question whether there is any such thing as “the Self204”, often equated with the Cartesian Ego205which is what is – naturally – self-conscious206 and is supposed to have this FPP. Some contemporary philosophers argue that the Self is an illusion that the brain generates. Others – such as Hume207 – have argued; and others – such as Galen Strawson – do argue that when they introspect, they find no evidence of a persisting Self. I don’t know where they are coming from, as I can’t think of anything more certain. But a Buddhist-inspired208 “no-self” view makes the animalist’s task easier, if maybe less interesting.
In-Page Footnotes:
Footnote 56:
- I have a developing Note on the Singularity.
- It is based on a Time Magazine interview with Ray Kurzweil way back in February 2011.
- See "Grossman (Lev), Kurzweil (Ray) - 2045: The Year Man Becomes Immortal".
- Things have moved on since then.
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