NOTE-166: Personal Identity and Ethics (SEP)

Contribution

A new SEP survey (replacing Shoemaker’s) of the practical significance of personal identity. It organises the literature around the gap between what we are (a persistence criterion) and what matters (the relation that grounds prudential concern, responsibility and moral status). It follows that gap through prudence, responsibility, the beginning and end of life, and normative ethics, and ends with the methodological question of which way the dependence runs. As a survey it adds no new argument; its contribution is the organisation and a 2025 bibliography.

Key insight

Almost every ethical question that seems to hinge on “is that the same person?” turns out, on inspection, to hinge on some other relation: psychological continuity, connectedness, a capacity to value, critical interests, or the presence of consciousness. Identity comes apart from these under fission, and even animalists concede that what matters is psychological. So the practical debates are really about what matters, and it is an open question whether that is fixed by metaphysics first or co-constructed with ethics in reflective equilibrium.

Assumptions

Premises and authorities.

• “Identity” means numerical persistence through time (§1), distinct from qualitative identity (twins) and from social or political identity. The entry sets the latter aside.
• Psychological criterion (§2): “person X at time1 and person Y at time2 are the same person if and only if X is uniquely psychologically continuous with Y” (S. Shoemaker 1970, 1984; Parfit 1973, 1986). Continuity is an overlapping chain of direct connections (Reid’s brave-officer case) and is all-or-nothing; connectedness comes in degrees.
• Biological criterion (§4): X is identical to Y “if and only if there is biological continuity between X and Y”, i.e. the same biological life (Olson 1997; DeGrazia 2005). Its consequence, that we are essentially human organisms, is animalism.
• Thought experiments carry normative, not empirical, weight (§5): they ask under which conditions one should care, not when people do (with Wilkes 1988 cited for the critique of the method).
• Uniqueness: numerical identity cannot hold one-to-two, which is why fission separates identity from continuity (§§2–3).

Key results

What the entry reports, by section.

• §3. Parfit’s fission case: both recipients are continuous with me, neither is me, yet I should care about their pain as my own. So what matters for prudence, and arguably morality, is not identity as such. It yields the four candidate views (a)–(d).
• §4. The cerebrum-transplant case is the main challenge to the biological view. The reply is that it is irrelevant in everyday cases and that the persistence relation and the relation that matters may come apart (Olson 1997: 70; 2022).
• §5 Prudential concern. Heavy weight on connectedness implies “a succession of overlapping multiple selves” and a discount rate on self-concern. Continuity better accommodates intentional character change (Merricks 2022). The compromise (both matter) reduces but preserves concern. Uniqueness may matter for positional goods: sole ownership, a unique partner, a unique title (Johnston 1992, 1997; Wolf 1986; Unger 1990). McMahan holds a late-stage dementia patient is the same person by continuous momentary consciousness plus brain continuity, but warrants somewhat reduced prudential concern.
• §6 Responsibility. The positions range from identity (Locke, Butler, Reid) to continuity (amnesia does not excuse; Glannon 2019) to degree-sensitive connectedness (Parfit’s Russian nobleman, 1984: 325f). The accountability/attributability distinction (Wolf, Watson, D. Shoemaker) lets severe dementia remove accountability while leaving some attributability. Whether punishing the demented makes sense depends on the theory of punishment (Hallich 2021; Dufner 2013).
• §7 Abortion. Marquis’s future-like-ours argument presupposes both biological identity (I was a fetus) and a psychological account of what gives life value. The critique: the fetus lacks the psychological relations that make a future “ours”, which makes identity irrelevant (Conee 1999; D. Shoemaker 2010). Verdict: biological views support a prohibition more strongly than psychological ones, but do not force it.
• §8 Death and advance directives. Whole-brain death is read as accommodating both accounts; higher-brain death assumes a psychological one (Veatch, McMahan), with proposals for personal choice of the standard. For Margo, most people take the demented patient to be identical to the earlier adult (a biological view or a lowered psychological threshold), but few argue that identity is what decides it (Dresser 1986 is the exception). Dworkin: critical interests, so respect the directive. Jaworska: the remaining “capacity to value”, so not necessarily.
• §9 Separateness of persons. Rawls: utilitarianism “does not take seriously the distinction between persons”. Parfit: reductionism weakens separateness, and so weakens objections to utilitarianism, and favours prioritarianism. Taurek and limited aggregation (Voorhoeve 2014); Nozick’s side constraints; Sidgwick’s rational egoism and Brink’s self-extended egoism; contractualism (Rawls; Scanlon). Verdict: separateness is too unspecific to support any one theory and may work at best as a negative argument against unrestricted utilitarianism (Rawls 1974; Brink 1993; D. Shoemaker 2007, 2009; McKerlie 1988).
• §10 Methodological alternatives. Separateness as a normative ideal (Rawls 1974). Dependence possibly running from ethics to what matters (Scheffler 1982; Darwall 1982). Korsgaard’s (1989) practical necessity of viewing oneself as unified, both diachronically (plans) and synchronically (“We only have one body to act with”). Narrative identity and Schechtman’s characterization question.
• §11. Three open questions: the correct theory of identity; whether identity or its constituent relations matter; and the priority between identity and ethics (fixed foundation vs reflective equilibrium).

Claims

id	claim	strength	support
C1	Fission shows identity and psychological continuity can come apart, and that continuity, not identity, grounds special prudential concern	reported argument (Parfit), thought experiment	§3, Parfit 1984: 254f
C2	Biological-view proponents generally concede that psychological relations are what matter ethically	reported consensus, cited	§4, §5: Olson 1997: 70; 2022; DeGrazia 2005
C3	Weighting connectedness heavily implies a discount rate on self-concern and near-parity with concern for others	reported inference	§5
C4	Biological views support prohibiting abortion more strongly than psychological views, but do not force it	the author’s synthesis	§7 (“Overall, one can say …”)
C5	Numerical identity is not decisive for the validity of advance directives; critical interests or the capacity to value are	reported positions (Dworkin 1993; Jaworska 1999)	§8
C6	Appeals to the separateness of persons have been used to support incompatible theories and so cannot by themselves support any one	the author’s synthesis with citations	§9: Rawls 1974; Brink 1993; D. Shoemaker 2007, 2009
C7	The dependence may run from ethics to what matters rather than the reverse	reported view	§10: Rawls 1974; Scheffler; Darwall; Korsgaard 1989
C8	The correct theory of identity, whether identity matters, and the metaphysics–ethics priority are all unsettled	the author’s conclusion	§11

Concepts

• numerical vs qualitative identity: being one and the same thing vs being exactly alike (§1).
• psychological connectedness: direct psychological connections (memories, intentions, beliefs, desires, perhaps traits), a matter of degree (§2).
• psychological continuity: overlapping chains of strong connectedness; transitive and all-or-nothing (§2).
• biological continuity: sharing the same biological life, or no abrupt radical change in the life-sustaining parts (§4).
• animalism: we are essentially human organisms (§4).
• what matters: the relation that grounds special prudential concern and related ethical attitudes, as distinct from the persistence relation (§3).
• special prudential (egoistic) concern: the distinctive concern one has for one’s own future (§3, §5).
• accountability vs attributability: responsibility requiring an understanding of one’s wrong vs merely fitting ascription of attitudes (§6).
• critical interests: interests grounded in judgements about the value of one’s life as a whole (Dworkin; §8).
• separateness of persons: numerical distinctness of individuals, and its diachronic flip side, the unity within a life (§9).
• characterization question: when psychological features, experiences and actions are properly described as a particular person’s (Schechtman; §10).

Connections

Metaphysical thesis defended or presupposed. The entry defends no metaphysical thesis. It presents two metaphysical accounts of persistence (a reductionist psychological criterion and animalism) and Parfit’s reductionism about what matters, and it treats the direction of dependence between metaphysics and ethics as open (§§10–11). It presupposes that “identity” in the relevant sense is numerical persistence and that identity is one-one. The metaphysics tag is justified as a secondary tag. identity is a sound primary tag, though ethics would be equally defensible: six of the eleven sections are applied or normative ethics.

Links in this record.

• LIT-136 (Floridi, informational personal identity): Floridi deflates exactly the diachronic questions the entry treats as open, making them purpose-relative (“teleological”) questions at a level of abstraction. The entry’s §10 (ethics may fix what matters) is the closest mainstream counterpart to that deflation, and its narrative accounts (Schechtman) are the ones Floridi criticises for lacking a principle of unity.
• LIT-138 (The Depth of the Body): makes the same kind of move from metaphysics to ethics for body parts, with a disclaimer that its ethics does not strictly depend on the metaphysics, which bears on this entry’s §11 priority question.
• LIT-142 (Meincke, process view of pregnancy): bears on §7’s premise “each of us was once a fetus”.
• LIT-206 (Goldstein & Lederman) and LIT-111 (Birch): the entry’s fission case and “what matters” framework are the standard tools for questions about copied, forked or per-conversation AI instances. The entry itself does not discuss AI, uploading or duplication beyond the fission case.
• LIT-120 (Welfare Subjects and Autopoiesis) and LIT-146 (The Moral Status of Animals): §7’s status-based arguments (“irrespective of what they will later develop into”) are the synchronic moral-status question those works address.

Bearing on the record

It carries nothing for ML practice, and there is no Anthology document it should inform. For nucleation it is the reference map for the identity–ethics interface, and the natural citation for Parfit’s fission argument and the “what matters” distinction when the record discusses copying or forking agents. The record should cite it as Dufner (2025), replacing Shoemaker’s entry, and should not cite it for any claim that identity settles an ethical question.

Limitations

• It is a survey. Its own syntheses (C4, C6) are brief and hedged.
• Coverage is of the analytic persistence debate. Four-dimensionalism, constitution views, Johnston’s later work and non-Western accounts are absent or mentioned only in passing, and the social or political sense of identity is explicitly excluded (§1).
• There is no treatment of duplication or uploading technologies beyond the fission case, and nothing on artificial agents.
• The methodological section (§10) shows that ethics may drive what matters, but does not assess whether that makes the persistence question practically idle.

Open questions

• The three the entry closes with (§11): which theory of persistence is true; whether identity or its constituent relations matter; and the direction of priority.
• How much weight continuity versus connectedness should get (Parfit “left open how much relative weight”, §5).
• Whether separateness can do more than negative work against unrestricted utilitarianism (§9).

Corrections to the seeded skim

• The dossier’s open item “Confirm whether this 2025 entry replaced an older SEP entry” is settled by the page itself. “Other Internet Resources” lists David Shoemaker, “Personal Identity and Ethics”, SEP Spring 2025 Edition (plato.stanford.edu/archives/spr2025/entries/identity-ethics/) with the note “[This was the previous entry on this topic in the Stanford Encyclopedia of Philosophy – see the version history.]”. The acknowledgments thank Shoemaker “for his inspiring earlier entry”. So Dufner’s is a new entry replacing Shoemaker’s at the same URL, and “First published 30 June 2025” dates the replacement, not the topic’s first SEP entry. Any citation of the URL before mid-2025 refers to Shoemaker’s text.
• The LIT summary says the metaphysical questions “jointly settle a family of ethical questions”. The entry says less and repeatedly shows the opposite. Accounts “can support competing answers” (preamble). For abortion, psychological continuity may matter “irrespective of whether we are numerically identical with fetuses” (§7). For death, “what is relevant … is not whether someone’s identity has been preserved” (§8). For advance directives, “numerical identity is not decisive” and Dworkin’s critical interests go beyond both criteria (§8). Biological theorists themselves separate what preserves identity from what matters (Olson 1997: 70; §4). The appeal to separateness “is not specific enough to lend positive support to a particular ethical view” (§9). The better summary: the metaphysics constrains, but rarely settles, the ethics.
• The dossier says §3 “uses a fission/branching case to argue” that continuity matters. The entry reports Parfit’s argument (triplet-sisters version, Parfit 1984: 254f) and then separates four candidate views of what matters: (a) numerical identity as psychological beings, (b) continuity, (c) connectedness, (d) both (Parfit 1984: 215, 313). It does not endorse (b).
• The dossier’s §§9–10 bullet reduces §10 to “metaphysical fact or normative ideal”. §10, “Methodological Alternatives”, also presents the view that the dependence “might, in fact, run from ethics to the relations that matter”. Moral theories generate ideals of personal unity: utilitarianism fits persons as “containers”, Kantianism needs strong diachronic unity (Scheffler; Darwall). Korsgaard’s agency argument holds that we must view ourselves as unified whatever the psychological facts. Narrative accounts (Schechtman’s “characterization question”) are also placed here. This is where the §11 priority question comes from.
• The dossier omits §5’s positions beyond Parfit: McMahan’s momentary-consciousness criterion for dementia (McMahan 2002: 495f), the uniqueness-matters view (Johnston, Wolf, Unger), and the discount-rate consequence of weighting connectedness.
• metaphysics tag: justified — §§1–4 set out rival metaphysical accounts of persistence (psychological criterion, animalism) and §§10–11 pose the metaphysics–ethics priority question explicitly; but most of the entry is applied ethics, so the tag is rightly not primary.