Contribution
The chapter makes personal identity a question of its own, distinct from the identity of substances and from the identity of the living human animal. It gives an answer, sameness of consciousness, that is independent of what the thinking substance is. It also supplies the cases the later literature is built from. Before it, the identity of a person was assumed to follow from the identity of a soul or a body. After it, there is a stated psychological criterion, and a set of cases in which soul, body and person come apart.
Key insight
“Same” is incomplete until one says same what. Identity is fixed by the idea the name stands for (§7, §28): a mass is the same while its particles are, a plant or animal or man while its organised life continues, and a person while its consciousness does. So the question “is this the same person?” is answered by consciousness, whatever the answer to “is this the same substance?” turns out to be.
Assumptions
- Ideas fix identity conditions. “Such as is the idea belonging to that name, such must be the identity” (§7). The chapter’s results depend on the reader sharing Locke’s ideas of man (a body “of a certain form”, §8) and of person (§9).
- Consciousness accompanies all thinking. “It being impossible for any one to perceive without perceiving that he does perceive” (§9).
- Substance is unknown. The chapter repeatedly brackets whether the thinking thing is material or immaterial, simple or compound (§§17, 23, 27). Its conclusions are meant to hold on either hypothesis.
- Divine goodness. That consciousness of a past action is never transferred to a substance that did not do it cannot be shown “from the nature of things”, and is “best resolved into the goodness of God” (§13).
Key results
- Principium individuationis (§3). It is “existence itself; which determines a being of any sort to a particular time and place, incommunicable to two beings of the same kind”. Two things of one kind cannot be in one place at one time, and one thing cannot have “two beginnings of existence” (§1).
- Masses and living things (§§3–6). A mass of atoms “is no longer the same mass” if one atom is added or taken away. An oak, a horse and a man are the same while they partake of “the same continued life” in “constantly fleeting particles of matter” (§6). A watch is the analogy for an animal, with the difference that in the animal “the motion coming from within” (§5).
- Same man (§§6, 8). If the same soul made the same man, Seth, Ismael, Socrates, Pilate and Caesar Borgia might be one man (§6). A rational parrot would still be called a parrot, and a creature of human shape without reason a man (§8, with Temple’s account of Prince Maurice’s parrot). So “man” is a body “so and so shaped” with a mind joined to it.
- Person and personal identity (§9). A person is “a thinking intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing, in different times and places”. Its identity reaches “as far as this consciousness can be extended backwards to any past action or thought”.
- Substance does not decide it (§§10–14, 23–25).
- Different substances united “by the same consciousness” make one person, as different particles united by one life make one animal (§10).
- Whether consciousness can pass between thinking substances cannot be settled by us; if it can, “two thinking substances may make but one person” (§13).
- An immaterial spirit stripped of all memory of a former life begins a new person. The man who believed his soul had been Socrates’s, or Nestor’s, is not the same person with them (§14).
- Day-man and night-man: two “incommunicable consciousnesses” acting one body by turns are two persons, and one consciousness acting two bodies by turns is one person (§23).
- Man and person come apart (§15). The prince’s soul, “carrying with it the consciousness of the prince’s past life”, in the cobbler’s body is “the same person with the prince”, but “the same cobbler to every one besides himself”.
- The boundary of the self (§§11, 17, 18, 25). A limb is part of the self while consciousness reaches it, and no part once cut off. If consciousness went with a severed little finger, “the little finger would be the person, the same person” (§17). If the body kept its own separate consciousness after the separation, it “would not at all be concerned” for the finger (§18).
- Forgetting and drunkenness (§§20, 22). Total, irretrievable forgetting separates the forgotten actions from the person but not from the man, and “human laws not punishing the mad man for the sober man’s actions” show the sense of mankind. Drunkards are punished anyway “because the fact is proved against him, but want of consciousness cannot be proved for him” (§22); at the Great Day, no one will answer for what he knows nothing of.
- Person a forensic term (§26). “It is a forensic term, appropriating actions and their merit; and so belongs only to intelligent agents, capable of a law, and happiness, and misery.” Punishment for an act one cannot be made conscious of differs not at all from “being created miserable”.
- Conclusion (§§28–29). “The difficulty or obscurity that has been about this matter rather rises from the names ill-used, than from any obscurity in things themselves.” Whatever complex idea one takes “man” to be, “the same existence continued preserves it the same individual under the same denomination”.
Claims
| id | claim | strength | support |
|---|---|---|---|
| C1 | Identity conditions depend on the kind: mass, life, consciousness | moderate | argued from the oak, horse and atom cases (§§3–6) and the parrot (§8); the dependence on “ideas” is asserted (§7) |
| C2 | Two things of one kind cannot occupy one place at one time, and one thing cannot have two beginnings | asserted as evident | §1; “we never finding, nor conceiving it possible” |
| C3 | Personal identity consists in sameness of consciousness, reaching as far back as consciousness extends | the thesis, argued by cases | §§9–10, 16–17, 23; never derived from C1 except by naming the idea of person |
| C4 | Personal identity is independent of identity of substance, material or immaterial | moderate, conditional on our ignorance of substance | §§10–14; the transfer of consciousness between substances is left open and then closed by appeal to God’s goodness (§13) |
| C5 | Same man and same person come apart | strong as conceptual separation, given C1 and C3 | prince and cobbler (§15); day-man and night-man (§23) |
| C6 | What consciousness reaches is part of the self, and nothing else | intuition | the little finger (§§11, 17); asserted “as every one who reflects will perceive” |
| C7 | Personal identity grounds just reward and punishment; “person” is a forensic term | moderate as a conceptual link; the legal evidence is reinterpreted, not followed | §§18, 26; drunkard and sleepwalker cases explained away by human ignorance (§22) |
| C8 | The difficulties about identity come from ill-used names | asserted | §28 |
Concepts
- identity / diversity — the ideas formed by comparing a thing existing at one time and place with itself existing at another (§1).
- principium individuationis — existence itself, fixing a being to a time and place (§3).
- man — an animal of a certain shape; the same man is the same continued life in one organised body (§§6, 8).
- person — a thinking intelligent being that can consider itself as itself in different times and places (§9); “the name for this self” (§26).
- self — “that conscious thinking thing … which is sensible or conscious of pleasure and pain, capable of happiness or misery, and so is concerned for itself, as far as that consciousness extends” (§17).
- consciousness — never defined. It is “inseparable from thinking” (§9), “a present representation of a past action” (§13), and the thing that can be “extended” backwards and forwards.
- forensic — of persons: the term that appropriates actions and their merit (§26).
Connections
- Hume’s “Of Personal Identity”, filed beside this reading, takes up Locke’s analogy between the identity of plants and animals and the identity of persons, and treats both as fictions of the imagination. Hume names “of late years in England” as the place the question became great, and in his Appendix he says “most philosophers seem inclin’d to think, that personal identity arises from consciousness”, which is this chapter’s thesis.
- Parfit’s “Personal Identity”, filed beside it, cites §18 (in Yolton’s edition) as the place where division is “implicit”. The finger that keeps its own consciousness is a case of one person becoming two. Parfit’s quasi-memory answers Butler’s charge, which Parfit names, that Locke’s account is circular.
- Survey (LIT-130, NOTE-166). The survey begins its psychological criterion and its responsibility section with Locke, Butler and Reid.
- Velleman (LIT-292, NOTE-268). Velleman reads Locke as making survival “a matter of memory alone”. The chapter speaks of “consciousness” of “thoughts and actions” and of concern for one’s own happiness (§§17, 25–26). It is wider than memory in what it says, though every case it uses is a case of remembering.
- Floridi (LIT-136, NOTE-130). That reading reports Floridi holding that Locke was right to distinguish kinds of sameness question and wrong to commit ontologically. §28’s diagnosis, that the difficulty lies in names, not in things, is already half of Floridi’s deflation.
- Dennett (LIT-405). The brain-in-a-vat story is the prince and the cobbler with radio links. Dennett’s narrator says a legal argument “might have appealed to” Locke; the chapter’s forensic person is the reason.
Bearing on the record
No THEORY document in the record cites this chapter. It bears on the record’s treatment of AI subjects only through its descendants: Birch’s persisting-interlocutor argument (LIT-111, NOTE-183) rests on Parfit’s Relation R, which is Locke’s criterion with quasi-memory in place of memory and with causal continuity added. The chapter carries no instruction for machine-learning practice.
Note of 2026-10-16: THEORY-546 now cites LIT-464 as a source.
Limitations
What is shown and what is asserted:
- Shown, as conceptual separation: that “same man”, “same substance” and “same person” can be given different conditions, and that cases can be described in which they diverge (C5).
- Asserted, not shown: that the conditions of personal identity are those of consciousness (C3). The cases make the criterion vivid; they rely on the reader’s agreeing that the prince is in the cobbler.
- Undefined: “the same consciousness”. Locke grants that it is “not the same individual act” (§13), so it is a relation between acts, and he does not say which. This is the gap Butler and Reid pressed, which the chapter does not anticipate.
- Closed by theology: whether false consciousness of another’s act could make one the same person is left to “the goodness of God” (§13).
- No transitivity. The chapter does not consider that consciousness reaching back from A to B and from B to C need not reach from A to C. That is Reid’s brave-officer objection, later the reason for Parfit’s distinction between connectedness and continuity.
Open questions
- What relation between a present act and a past one makes them “the same consciousness”? The chapter’s only gloss, “a present representation of a past action”, would include false memory, which §13 sees and does not resolve.
- Does Locke’s person persist through gaps in consciousness, such as sleep? §10 says the doubt such gaps raise “concerns not personal identity at all”, but the criterion as stated in §9 would need overlapping chains to say why.
Corrections
- To Project Gutenberg eBook #10615. Its chapter has 31 sections, not 29. It omits the account of Prince Maurice’s parrot from §8, and the sentence “For, though punishment be annexed to personality … want of consciousness cannot be proved for him” from §22. It garbles §14 (“some of the particles of smaller that were once a part of Nestor” for “particles of matter … ; the same immaterial substance”) and §24 (“so that I cannot upon recollection join” for “if there be any part of its existence which I cannot upon recollection join”). It reproduces the 1690 first edition’s title page over a later edition’s text, though the 1690 edition lacked this chapter. Cite another text.
- To the brief’s description of the edition: none needed. “Added in the 2nd edition, 1694” is right.