Will I Still Be Me Tomorrow? Personal Identity from the Ship of Theseus to the Teletransporter

The Hook: The Machine That Stops, and the Machine That Keeps Running

Picture a live migration. A virtual machine has been running for months in a data center in Frankfurt. The hypervisor freezes it for a few milliseconds, writes the complete state — memory, CPU registers, open file descriptors, TCP connections — into a snapshot, ships it to Amsterdam, restores it there, and lets the machine continue. In Frankfurt, the original memory is released. From the monitoring system's point of view, nothing happened: the same instance ID, the same uptime, the same running processes.

Now change one detail. The hypervisor does not release the memory in Frankfurt. It simply lets the original machine keep running. Now two instances exist with an identical state history, both with the same uptime, both convinced they are "the" machine that booted months ago. Which one is it?

The question sounds like an operations problem, and in one sense it is — anyone who works with replication, snapshots, and distributed state has learned that "the same instance" is not a physical fact but a convention you have to define carefully, or else two masters run in parallel and the data diverges. But it is also, quite literally, one of the oldest and most stubborn problems in philosophy. Because what is being asked here about virtual machines applies to you.

You are made today of mostly different atoms than you were ten years ago. Your memories of 2016 are patchy, partly reconstructed, partly simply wrong. Your political views, your taste, your fears have shifted. There is no single material or psychological property that has been passed through unchanged from that state to this one. And yet there is no doubt — no everyday doubt, at any rate — that you are the same person. You are liable for contracts that person signed. You serve a sentence that person incurred. You save money because the same person will need it in thirty years.

So what does this identity consist in? This article walks the whole distance: from an ancient ship, through a chapter that John Locke inserted retroactively into an already-published book in 1694, through two counterattacks that nearly destroyed it, to Derek Parfit's unsettling conclusion that the question of identity may be the wrong question. And because this vault is about checkable claims, the journey does not end in speculation: there are now robust empirical findings about what people actually treat as identity-bearing — and the answer is surprising.

Part 1: Asking the Question Properly

Two Kinds of "the Same"

Before you can answer, you have to clear away an ambiguity on which most everyday discussions founder. "Is that still the same person?" can mean two entirely different things.

The first meaning is qualitative identity: similarity. When we say someone "isn't the same after the illness," we mean that their properties have changed. That is a matter of degree; there is more and less of it.

The second meaning is numerical identity: being one. The question of whether the being that was in Frankfurt in 2016 and the being sitting here today are one and the same thing or two. That is not a matter of degree. Two things are either one or not; there is no half-oneness in logic.

Eric Olson, who wrote the authoritative treatment of the topic in the Stanford Encyclopedia of Philosophy, calls the philosophically interesting version the persistence question: What makes a person existing at one time identical to a being existing at another time? Or, in the first person: Which future being am I?

This precision is not pedantry. It is the reason the problem is hard at all. If identity were a matter of degree, every case could be dissolved with "somewhat the same person." Because it logically cannot be, every borderline case forces a sharp answer — and that is exactly where every theory breaks.

The Ship and Its Sharpening

Plutarch reports in his Life of Theseus (chapter 23) of a ship the Athenians preserved in memory of Theseus's voyage. Over the centuries the planks rotted and were replaced one by one, until no piece of the original wood remained. Plutarch explicitly notes that the philosophers argued over whether it was still the same ship.

Thomas Hobbes sharpened the example in De Corpore (1655) into a genuine dilemma: suppose someone collects the discarded old planks and builds a second ship out of them. Now there are two candidates. One has the unbroken history, the continuity of form, function, and location; the other has exactly the original material. Both claims are strong, and they cannot both be right, because one thing cannot be identical with two different things.

For ships this is a conceptual curiosity you can settle with a convention if you must. For persons it is not, because here responsibility, care, inheritance law, and one's own fear of the future all hang on it. The ship is therefore only the warm-up exercise.

Part 2: Locke's Coup — Identity as Consciousness

A Chapter Added After the Fact

When John Locke published his Essay Concerning Human Understanding in 1689, it contained no theory of personal identity. Only for the second edition of 1694 did he add chapter II.xxvii — according to Jessica Gordon-Roth's SEP entry, at the urging of his correspondent William Molyneux. That afterthought of a chapter has become one of the most influential texts in modern philosophy.

Locke's decisive move is a distinction almost nobody before him had drawn so sharply. He separates three concepts the tradition had run together:

• Substance — the metaphysical bearer, for instance an immaterial soul.
• Man — the living human organism, the animal.
• Person — "a thinking intelligent Being, that has reason and reflection" and can consider itself as itself.

These three can come apart. And that is precisely the point: personal identity, Locke says, consists neither in sameness of substance nor in sameness of organism, but in sameness of consciousness extending backward into the past. As far as my consciousness reaches over a past action or experience, that far my person extends.

Prince and Cobbler, Day-Man and Night-Man

Locke supports this with two thought experiments that have appeared in every seminar since.

In the first, the soul of a prince — along with the consciousness of his past life — migrates into the body of a cobbler whose own soul has left that body. Who wakes up there? Locke answers unambiguously: the person of the prince, in the shape of the man the cobbler. The person follows consciousness, not the body.

In the second experiment, two entirely sealed-off consciousnesses alternately inhabit one and the same body — a day-man and a night-man who know nothing of each other. Locke judges them to be "as distinct persons as Socrates and Plato," even though it is the same man and the same soul.

"Person" as a Forensic Term

The most often overlooked but deepest part of Locke's argument is his reason why consciousness should be what matters. "Person," he writes, is a forensic term — a term whose function is the appropriation of actions and their merit. The concept exists because we want to hold someone responsible for something. And you can only meaningfully hold responsible a being that can recognize the deed as its own.

Locke thereby inverts the direction of explanation. He does not ask: what is identity, and what follows from it for responsibility? He asks: what do we need the concept of a person for — and which criterion serves that purpose? That is a functionalist move, and it will matter again at the end of this article.

Part 3: Two Counterattacks That Nearly Destroyed Everything

Locke's theory was so compelling that it immediately provoked massive resistance. Two objections, both from the eighteenth century, remain the standard touchstones today.

Butler: Circularity (1736)

Joseph Butler, in The Analogy of Religion (1736), formulated the charge of circularity. Genuine memory, Butler argued, is not simply the appearance of an image in your head. To remember an experience is to remember an experience you yourself had. If I "remember" a scene I only saw in a film, that is not a memory but a confusion.

But that means the concept of genuine memory already presupposes personal identity. To decide whether someone really remembers, you must already know whether they are the person who lived it. Consciousness can then reveal identity but not constitute it. Butler's objection does not target the criterion's usefulness but its claim to be constitutive.

Reid: The Brave Officer and Transitivity (1785)

Thomas Reid, in his Essays on the Intellectual Powers of Man (1785), delivered the technically harder blow. His example has become famous:

A boy is flogged for stealing apples from an orchard. As a young officer he captures an enemy standard — and in doing so remembers the flogging. As an old general he remembers capturing his first standard, but he no longer remembers the flogging.

Now do the arithmetic. By Locke's criterion: the officer is the boy (memory present). The general is the officer (memory present). The general is not the boy (no memory). But numerical identity is a transitive relation: if A = B and B = C, then necessarily A = C. Locke's criterion delivers a result that is logically impossible.

The Repair: Psychological Continuity

Reid's objection is so precise that it permitted a precise repair — and that repair has prevailed. Instead of direct memory, modern theories require psychological continuity: a chain of overlapping psychological connections. The general is connected to the officer, the officer to the boy; that suffices, because the chain runs through as a whole even though no single link reaches from beginning to end. Formally, the intransitive relation of direct memory is replaced by its transitive closure.

At the same time the notion is broadened: not only memories, but beliefs, intentions, preferences, character traits — everything causally produced by its predecessor state. In one stroke this also solves the problem of dreamless sleep and general anesthesia, in which no memories form but the chains remain intact.

On Olson's account, this psychological-continuity theory is precisely the position that has dominated among Western philosophers since the early twentieth century. But it is not unchallenged.

Part 4: Williams's Counterstrike — How the Question Is Asked Decides the Answer

In 1970 Bernard Williams published a paper in the Philosophical Review titled "The Self and the Future," one of the most elegant arguments in analytic philosophy — because it does not claim the psychological theory is false, but shows that our intuitions about it depend on the narrative perspective.

Williams tells the same situation twice.

First telling (third person): Two people, A and B, are placed in a machine that completely swaps their psychological states. Afterward, A-body has all of B's memories and character, and vice versa. It is announced in advance that afterward one of the two bodies will be tortured and the other rewarded, and A is allowed to choose which body gets which. Almost everyone thinks it rational for A to designate the B-body for torture — because A will be in the B-body afterward. The psychological theory triumphs.

Second telling (first person): You are told: tomorrow you will be tortured. Beforehand, all your memories will be erased, so that you will no longer remember the announcement. Further: you will additionally have false memories implanted, namely those of another person, and your character replaced by that person's character. And then the torture happens.

Williams's observation: in this telling, the dread grows with every step instead of vanishing. None of the additional measures — amnesia, false memories, character replacement — reads as a consolation. They sound like aggravations. And yet the second telling describes exactly the same physical procedure as the first.

This is a methodologically deep result. It means our intuitions about personal identity are not stable under reformulation. Anyone who grounds a theory in intuitions must know that the intuitions themselves are movable.

Remarkably, exactly this conjecture was later tested empirically. Michael Bruno and Shaun Nichols published a study in Philosophical Psychology in 2010 testing Williams's framing hypothesis: the manner of presentation does in fact affect whether people judge psychological continuity to be necessary. At the same time they found that when asked open-ended questions about what is required for survival, psychological continuity clearly dominates, and that this dominance largely persists even after confrontation with conflicting scenarios. Williams was right about the framing effect — and the psychological theory nonetheless retains the intuitive upper hand.

Part 5: Parfit — Fission and the Dissolution of the Question

In 1984 Derek Parfit published Reasons and Persons with Oxford University Press, a book in four parts whose third part permanently reset the debate over personal identity. Parfit's approach is characteristic: he takes the psychological theory seriously, drives it into a case where it collapses — and draws from this not the conclusion that it is false, but the far more radical conclusion that the question itself is overrated.

The Teletransporter

Parfit's entry point is the teletransporter. You step into a booth on Earth. A scanner records the precise configuration of your atoms, the information is sent to Mars, and there a replicator builds, from local matter, a human being configured exactly as you were. Your body on Earth is broken down in the course of the scan. The person on Mars wakes up, remembers stepping into the booth, has your plans, your debts, your preferences.

Is he you? That is exactly the snapshot-restore question from the hook, only with your own state. The psychological-continuity theory says yes; every body-centered theory says no. Up to here it is a clean duel between two positions.

Fission

Then Parfit sharpens it. The scanner on Earth is modified so that it does not destroy the body. Or, in the even sharper variant Olson discusses in the SEP: your two cerebral hemispheres are separated and transplanted into two different bodies. Each hemisphere carries enough to establish psychological continuity. Out come two people — call them "Lefty" and "Righty" — both of whom are psychologically continuous with you.

Now the psychological theory is in a logical trap. It says: Lefty is you. It says: Righty is you. But Lefty and Righty are obviously not identical with each other — they sit in different places, feel different things, will experience different things. Since identity is transitive, both cannot be true.

The classic evasions are both unsatisfying:

• The multiple-occupancy view: there were two people all along, temporarily sharing the same temporal parts, who now diverge. This saves the logic, but demands a four-dimensional ontology of temporal parts and the claim that two people are sitting in your chair right now, should fission ever befall you.
• The non-branching clause: a being is you only if it is psychologically continuous with you and no other being is as well. On this view you cease to exist at fission. This has the bizarre consequence Olson highlights: save one hemisphere and you survive; save both and you die.

"Identity Is Not What Matters"

This is exactly where Parfit's real move begins. He accepts that you cannot be identical with both successors in fission. But he asks: is that a loss?

Suppose you will be split tomorrow. Lefty and Righty will both continue your life, carry on your projects, remember your life. Is your situation as bad as ordinary death? Obviously not. Almost nobody would put fission on a par with annihilation. So there is something preserved in fission that ordinary death lacks — and that something is not numerical identity, because numerical identity is absent in both cases.

Parfit calls this something Relation R: psychological continuity and connectedness with the right kind of cause. His thesis: what should rationally concern us when we care about our survival is Relation R, not identity. Identity is merely the special case in which Relation R does not branch. The famous formula: identity is not what matters.

This has far-reaching consequences. First, survival becomes a matter of degree: Relation R comes in degrees, and there can be cases where the question "is that me?" has no determinate answer without any fact remaining unknown — the question is then empty, not open. Second, concern for one's own future becomes gradable: if my psychological connectedness to my self in forty years is weaker than to my self in forty minutes, then it is not irrational to weight them differently — which, for Parfit, does not mean we may neglect the distant future, since those affected exist whether or not they are "me." Third, death loses part of its terror, a thought in which Parfit himself saw an affinity with Buddhist teachings on the non-substantiality of the self.

I am of the opinion that Parfit's argument is the strongest reframing of this problem in the twentieth century — but it is a philosophical position, not an established finding, and it remains the object of sustained criticism.

Part 6: The Body Strikes Back — Animalism

The countermovement to this entire psychological tradition is animalism, argued most pointedly by Eric Olson in The Human Animal: Personal Identity Without Psychology (Oxford University Press, New York 1997; paperback edition 1999). His thesis is so simple it provokes: we are biological organisms. Our persistence conditions are therefore those of an animal — biological survival, metabolism, organismic continuity — and have nothing whatsoever to do with psychology.

Olson's strongest argument is not direct but indirect. He calls it the too-many-thinkers problem (also: the thinking-animal argument):

1. There is a human organism sitting in your chair.
2. That organism has a functioning brain and is therefore thinking and intelligent — indistinguishable in every respect from a person.
3. If you are not that organism, then there are two thinking beings where you are: you and the animal.

This generates three follow-on problems. It duplicates thinkers where we expected one. It duplicates persons, because the thinking animal also satisfies the usual criteria for personhood. And it creates an epistemic dead end: you could not know whether you are the psychologically persisting being or the animal, since both would have the same thoughts.

Defenders of the psychological theory answer either that organisms do not think in the relevant sense, or that personal pronouns refer by convention only to psychologically persisting beings. Both answers have their price.

Animalism's price is also high: it must reject the strong intuition that a brain transplant would move you into another body. For Olson that is merely an organ transfer. Notably, Williams already argued in this direction in 1970: transplanting a brain might simply be moving an organ, not a person — much like a liver.

Part 7: What the Evidence Says — and Why It Surprises

For centuries the debate was purely conceptual. For roughly two decades it has also been investigated experimentally, and three findings deserve particular attention.

It Is Not Memory That Counts, but Morality

Nina Strohminger and Shaun Nichols published a study in Psychological Science in 2015 (volume 26, issue 9, pp. 1469–1479) titled "Neurodegeneration and Identity." They surveyed relatives of patients with three different neurodegenerative diseases — frontotemporal dementia, Alzheimer's disease, and amyotrophic lateral sclerosis (ALS) — and used structural equation modeling to determine which kind of change explains perceived identity discontinuity.

The result contradicts the entire Lockean tradition. The strongest driver of perceived identity loss was damage to the moral faculty — not memory loss, not general cognitive decline, not the loss of personality traits in the broader sense. Frontotemporal dementia, which characteristically alters moral judgment and social behavior, produced the greatest identity discontinuity; ALS the least. For memory loss, no measurable independent effect on perceived identity persistence was found. In addition, perceived identity change fully mediated the relationship between disease and the deterioration of the caregiver–patient relationship.

This is a strong finding, and it fits Locke's own justification strikingly well — just not his criterion. Locke said "person" is a forensic, that is, a morally attributive term. If that is right, it is hardly surprising that people treat the moral structure of a human being as identity-bearing rather than episodic memory. Locke got the purpose right and the criterion wrong.

How Robust Are Our Intuitions?

Bruno and Nichols (2010, Philosophical Psychology 23(3), 293–312) confirmed Williams's framing hypothesis, as described above, while also showing that psychological features are treated as central in open-ended questioning. For the methodological debate this means: intuitions are evidence, but evidence with a known measurement bias.

Divided Perception, Undivided Consciousness

The fission argument leans heavily on the idea that two separated hemispheres yield two subjects — an idea that drew its plausibility from classic split-brain research, in which patients whose corpus callosum had been severed appeared like "two consciousnesses in one head."

This textbook view has been shaken. Yair Pinto and colleagues published the study "Split brain: divided perception but undivided consciousness" in Brain in 2017 (volume 140, issue 5, pp. 1231–1237). In two patients with complete transection of the corpus callosum they showed that the patients could respond accurately to stimuli appearing anywhere in the visual field, regardless of whether they answered verbally, with the left hand, or with the right hand. They could not compare stimuli across the visual half-fields — but they had full awareness of the presence of stimuli as well as well-above-chance recognition of location, orientation, and identity of stimuli throughout the entire visual field. The authors' conclusion: severing the connection divides perception, not consciousness and not response control.

Two patients is a small sample, and the interpretation of these findings is contested in the literature. But the consequence for philosophy is clear: the empirical foundation of the fission intuition is softer than the thought experiments assume. Anyone who infers two subjects from the split-brain finding is no longer arguing on secure ground.

Part 8: A Map of the Positions

Part 9: Why This Is Not a Seminar Question

The Advance Directive

German law recognizes the advance directive in § 1827 BGB — a provision that carried the number § 1901a BGB until the reform of guardianship and custodianship law took effect on January 1, 2023. Its principle: a person capable of consent specifies in advance which treatments they do or do not consent to, in case they later lose that capacity.

Metaphysically this is a remarkable construction. It grants the earlier self authority over the later one — discussed in philosophy as "precedent autonomy," a term coined by Ronald Dworkin in Life's Dominion (1993). And this is exactly where Parfit's argument strikes with full force. If psychological connectedness is a matter of degree and largely breaks down in severe dementia, by what right does the directive of a person bind, whose Relation R to the patient in question is now only thin?

Rebecca Dresser made precisely this case against Dworkin in 1995 in the Hastings Center Report (volume 25, issue 6, pp. 32–38) under the title "Dworkin on Dementia: Elegant Theory, Questionable Policy": the theory is elegant but questionable as policy, because it subordinates the current interests and current welfare of the demented patient to the wishes of a person who in relevant respects is no longer there. The opposing position holds that without binding advance directives, autonomy would have no grip on the end of life at all. This debate is not settled — but it is, and this is the point, the same debate as the one between Locke, Parfit, and Olson, only with legal consequences.

Responsibility Across Time

A person serves a sentence at sixty for an act committed at twenty-five. The justification of the punishment presupposes that it is the same person. Take Parfit seriously and responsibility becomes a matter of degree — a position Parfit explicitly entertained, and one that juvenile criminal law has in practice long acknowledged, albeit for other reasons. Anyone who finds the question of personal identity detached should explain what else the justification of punishment across decades rests on.

The Future You Save For

Psychological research on so-called future self-continuity has shown that people who experience their future self as more strongly connected to their present self are more likely to act in that self's favor — for instance, by saving. I am of the opinion that this is the most practically useful translation of the entire problem: the strength of Relation R to your self in twenty years is not something you merely observe, but something you help shape through projects, commitments, and narratives.

And the Digital Copy

Which brings us back to the hook. Anyone who operates systems has long since operationalized the very distinction at issue here — just not for themselves. A live migration is move semantics: the source state is invalidated after the cutover, which is why instance identity stays unproblematic. A snapshot with restore while the source keeps running is copy semantics, and then you need a fencing mechanism, because two instances with the same claim must not coexist. That is exactly the non-branching clause, implemented in software. Distributed systems do not solve the fission problem by answering who "the real" instance is; they solve it by forbidding the branch in the first place. The philosophical lesson is sobering and illuminating at once: the identity of instances over time is not something you find in the states — it is something a protocol establishes. Parfit's question is whether it is any different for persons.

The Central Takeaway

After twenty-three centuries of debate there is no criterion of personal identity that survives every case. That is not a failure of philosophy but a finding — and it has a practically usable structure.

The solid core is threefold. First: the question "am I the same person?" systematically conflates two questions — the logical one about numerical identity and the practical one about what matters in my continuing. Parfit's contribution is to have shown that the second can do without the first. Second: what people empirically treat as identity-bearing is not their memory but their moral character — Strohminger and Nichols found no independent effect for memory loss. Third: our intuitions about these cases are measurably dependent on formulation, and the empirical foundation of the sharpest thought experiments is softer than assumed.

The concrete call to action lies in inverting the question. Instead of asking "will I still be me in twenty years?" — a question that may have no determinate answer — the worthwhile question is: which connections between my present and my future self do I want to build actively? Because Relation R, unlike a metaphysical fact, is partly designable. Commitments that reach far, projects that take years, values you deliberately carry forward, memories you hold on to: all of it strengthens the chain that ties you to the being you act for today. And the inverse holds as well: an advance directive, a will, a long-term promise are not merely documents but attempts to take responsibility toward a later self, even though the connection will be weaker than it is today. Someone who has grasped that this connection is not guaranteed but built treats such decisions differently — more carefully, and with less taking for granted.

And if Strohminger and Nichols are right, something uncomfortable follows as well: if others identify you above all by your moral character, then the continuity that really counts is not a matter of your memory but of your integrity. You remain the same person to others to the extent that you hold the same things to be right.

A Closing Question for Reflection

Suppose you learn that the teletransporter you have used for business travel for years never worked the way you believed: each time, it completely disassembled you at the departure point and rebuilt you at the destination. All your memories, plans, and attachments are intact and seamless. Nobody — you included — ever noticed a difference.

Have you thereby learned that you have died several times in recent years? Or have you learned that dying is not what you thought it was? And if you hesitate: what exactly would be the fact that makes the difference between these two descriptions — and if none comes to mind, might it be that Parfit was right and the question is empty rather than open?

Cross-References in the Vault

This question pulls threads to several other investigations in the vault:

• What Mary Did Not Know: The Knowledge Argument and the Riddle of Consciousness – the sister question: not what persists over time, but what consciousness is at all and whether it can be exhaustively described physically.
• The Chinese Room: Searle and the Question of Whether Machines Can Understand – whether functional sameness suffices: the same question the teletransporter raises about your reconstruction.
• The Billions Barely Alive: Parfit's Repugnant Conclusion and the Ethics of Future Generations – Parfit's fourth part; the same reductionist method, applied to future persons.
• Three Pages Against 2,000 Years: The Gettier Problem and What Knowledge Really Is – the pattern of a centuries-old definition shattering on a few constructed cases.
• The Invented Memory: Why Recollection Is Not a Recording – and How Elizabeth Loftus Showed You Can Remember Things That Never Happened – empirical dynamite for Locke's criterion: if memories can be constructed and false, what does the memory theory rest on?
• The Half-Second Before the Will: Libet's Experiment and the Neuroscience of Free Will – the neighboring problem of agency, likewise with forensic consequences.
• The Promise on the Form: How the Crimes of Nuremberg Produced Informed Consent – and Why the Signature Still Means Less Than We Think – how consent works legally when the consenting and the affected self are not the same.
• Agreement Without a Vote: CRDTs and the Art of Conflict-Free Replication – how distributed systems handle diverging copies of the same state without having to declare one of them "the real one."

Sources

• Olson, E. T.: Personal Identity. Stanford Encyclopedia of Philosophy, first published 2002-08-20, substantively revised 2023-06-30. https://plato.stanford.edu/entries/identity-personal/
• Gordon-Roth, J.: Locke on Personal Identity. Stanford Encyclopedia of Philosophy, first published 2019-02-11, substantively revised 2025-09-29. https://plato.stanford.edu/entries/locke-personal-identity/
• Williams, B. (1970): The Self and the Future. The Philosophical Review 79(2), 161–180. https://philpapers.org/rec/WILTSA-2
• Parfit, D. (1984): Reasons and Persons. Oxford University Press, Oxford. Part 3 on personal identity.
• Olson, E. T. (1997): The Human Animal: Personal Identity Without Psychology. Oxford University Press, New York (paperback edition 1999). https://academic.oup.com/book/3191
• Bruno, M., Nichols, S. (2010): Intuitions about personal identity: An empirical study. Philosophical Psychology 23(3), 293–312. https://doi.org/10.1080/09515089.2010.490939
• Strohminger, N., Nichols, S. (2015): Neurodegeneration and Identity. Psychological Science 26(9), 1469–1479. https://doi.org/10.1177/0956797615592381
• Pinto, Y., Neville, D. A., Otten, M., Corballis, P. M., Lamme, V. A. F., de Haan, E. H. F., Foschi, N., Fabri, M. (2017): Split brain: divided perception but undivided consciousness. Brain 140(5), 1231–1237. https://doi.org/10.1093/brain/aww358
• Dresser, R. (1995): Dworkin on Dementia: Elegant Theory, Questionable Policy. Hastings Center Report 25(6), 32–38. https://doi.org/10.2307/3527839
• § 1827 BGB (Patientenverfügung / advance directive), version in force since 2023-01-01, formerly § 1901a BGB. https://dejure.org/gesetze/BGB/1827.html

Note: Personal identity is an open philosophical question; none of the positions presented is considered conclusively decisive. The empirical findings (Strohminger & Nichols 2015; Pinto et al. 2017; Bruno & Nichols 2010) are published, peer-reviewed studies whose interpretation is in part contested in the literature — the split-brain findings in particular rest on two patients. Where this article goes beyond the established state of knowledge, this is marked with "I am of the opinion that ...".

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