Locke’s chapter on personal identity is a masterpiece. Nonetheless, it is long, frequently repetitive, occasionally digressive, and, in a few places, downright confusing.
To help you find the most important parts and avoid the pitfalls, I summarized the central point of each section. I also colored the very most essential sections red: §§3–4, §§6–7, §§9–12, §§14–16, §§19–20, and §22. You should feel confident that you understand those; the rest are less important.
§1 How do you ask a question about identity? Answer: questions about identity involve comparing things at different times. Principle: two things of the same kind cannot exist in the same place at the same time. Conclusions drawn from the principle: one thing can’t have two beginnings and two can’t have one beginning.
§2 Three substances: God, finite intelligences (spirits), bodies. More on the principle from §1.
§3 Distinction between identity of mass of matter and identity of living things. Examples: colt grows to a horse and the sapling grows into a mighty oak. In both cases, the matter changes but animal or plant remains the same.
§4 Proposal about identity of living things. It depends on the organization of parts to continue the thing’s life.
§5 Analogy between living things and machines. Difference is that the “force” that drives machines is external while for living things it is internal.
§6 Definition: “man” is a human animal. Locke appears to argue for this with examples. But he’s really just defining the term “man.”
§7 What is the question about personal identity? There are three things: substance, man, and person. The question is whether the identity of one of them consists in the identity of the other. E.g. does being the same man over time consist in being the same substance over time? Or, does being the same person over time consist in being the same substance over time? (The substances would be either finite spirits or material bodies; see §2.)
§8 Story of the parrot. The point of this story is to reiterate Locke’s view that the term ‘man’ refers to a human animal, something with a living human body. The parrot has the qualities sometimes thought to be characteristic of human beings: it is rational and uses language. But it has a parrot’s body and so, according to Locke, it cannot be a man. As in §6, Locke is more insisting on a definition than he is proving a point. Still, he’s right to say that the parrot doesn’t have the same kind of body as a human being and he is allowed to say that he will use the word “man” to refer to a human animal.
§9 Definition: “person” is a thinking intelligent being with reason and reflection, that can consider itself as the same thinking thing at different points in time and space. Claim that consciousness is inseparable from thinking. The identity of the person across time depends on extending consciousness backwards in time, i.e. remembering having had the earlier person’s thoughts and experiences.
§10 Analogy: relationship of person to substance is like relationship between animal life and matter. The one can remain the same while the other changes.
§11 Evidence for Locke’s view. We think that anything that conveys sensory experiences is part of our selves. The fact that I am conscious (or aware) of feeling things through the fingers at the end of my hand is why I think of those fingers as belonging to me. Conversely, the fact that I am not aware of feelings through the fingers at the end of your hand is why I do not think of those fingers as belonging to me. (See also §17 below.)
§12 Is having the same substance a necessary condition of being the same person over time? Is having the same substance a sufficient condition of being the same person over time? Locke says it is not a necessary condition. An animal life can remain the same despite changes in the material substance that makes up its body. Locke proposes a parallel with personal identity and immaterial substance.
§13 Is having the same immaterial substance a necessary condition of being the same person?The “first part of the Question” is a reference to the first sentence of §12. Locke says that he is not sure if it is possible for the person to remain the same while the thinking substance changes. He would need to know more about what a thinking substance is. There is a confusing discussion about whether God would ever allow transferring one person’s consciousness to another’s thinking substance, such that the one person’s crimes would be transmitted to the second (p. 338, lines 13–18). This is confusing because transferring consciousness would only have that effect if persons were identical with substances, which is something that Locke denies throughout the chapter.
§14 Is having the same immaterial substance a sufficient condition of being the same person? The “second part of the Question” is a reference to the first sentence of §12. Locke says no. Example: the “very rational man” who believes he has Socrates’s soul but cannot remember having been Socrates. Locke: he isn’t the same person as Socrates.
§15 Person and man are distinct. One man (living human body) can have two different persons. And one person can occupy two different men. So being the same man is neither a sufficient condition of being the same person nor a necessary condition of being the same person. Example: the prince and the cobbler, body-switching.
§16 Being conscious of a past person’s thoughts and experiences is sufficient for being the same person over time. Example: if Locke remembered having seen Noah’s ark, then Locke would be the same person as the one that saw Noah’s ark. Note: §§14–15 implicitly show that being conscious of a past person’s thoughts and experiences is necessary for being the same person over time. That’s why the ‘very rational man’ is not the same person as Socrates and why the person who wakes up in the Prince’s body is not the same person as the Prince: neither is conscious of the relevant person’s thoughts and experiences and so neither can be same person as Socrates or the Prince, respectively.
§17 Consciousness is both necessary and sufficient for being the same person. If consciousness went with the little finger, the person would go with the little finger and not the rest of my body.See background on Aquinas and Hobbes.
§18 Self-concern and justice. Self-concern is directed towards the parts of your body that you can feel: you wouldn’t worry about feeling pain in the rest of your body if your consciousness went with a finger that had been cut off. (Think of it in reverse: you wouldn’t anticipate feeling pain in an amputated finger.) And the little finger could not be justly blamed or punished for things that the rest of the body did.
§19 Example: if waking Socrates cannot remember what sleeping Socrates did, it would be unjust to punish waking Socrates for the actions of sleeping Socrates.
§20 Objection: what if I forget something from last year. Does that mean I did not exist last year. Answer: the same man existed but not the same person. Evidence: the law does not punish Sober Man for what Mad (Drunk) Man did.
§21 Objection: how could there be two persons (Waking Socrates and Sleeping Socrates) in one man? Locke maintains that his system is less paradoxical than the alternatives.
§22 Objection: why do we punish sober people for what they did when they were drunk? Answer: human justice is imperfect. We can’t know if the sober person really does not remember so we guess. God will get it right.
§23 Another example: Day-man and Night-man. This is similar to waking and sleeping Socrates.
§24 Repeating the point about self-concern: if part of my body is cut off from my consciousness, I won’t think of it as part of myself. Similarly, I am not concerned about any immaterial substance that I am not aware of.
§25 And again with self-concern. We call “self” all and only those parts we are conscious of. That’s true for the parts of the body and, by extension, should be true of parts of an immaterial thinking substance as well.
§26 Again: self-concern and the justice of rewards and punishments. In the afterlife, we will be rewarded or punished for what we are conscious of having done, regardless of what material bodies or immaterial substances we inhabit in the afterlife.
§27 We don’t know how we think and have experiences. We don’t know if this is made possible by a material substance (like a brain) or an immaterial one (like a soul).
§28 Repeat initial point about how we have to specify what kind of thing we’re talking about in order to ask questions about identity (e.g. material substance, immaterial substance, living creature, or person.).
§29 Application to the idea of man. (I find this obscure.)
Locke’s example of consciousness going “along with” the little finger (§17) is obscure to us. But it actually tells us quite a lot about who he thought his opponents were. That is because the example of the little finger would have been a familiar to his readers.
St. Thomas Aquinas had used the little finger to illustrate his immaterialist doctrine that the person is identical with an immaterial soul. An immaterial soul does not have the properties of matter and so, Aquinas argued, it could be wholly in every part of the body. Thus it could be wholly in the little finger and wholly in the big toe and wholly in the right earlobe, and so on.
“… if the soul were united to the body merely as its motor, we might say that it is not in each part of the body, but only in one part through which it would move the others. But since the soul is united to the body as its form, it must necessarily be in the whole body, and in each part thereof. For it is … the substantial form of the body. Now the substantial form perfects not only the whole, but each part of the whole. For since a whole consists of parts, a form of the whole which does not give existence to each of the parts of the body, is a form consisting in composition and order, such as the form of a house; and such a form is accidental. But the soul is a substantial form; and therefore it must be the form and the act, not only of the whole, but also of each part. Therefore, on the withdrawal of the soul, as we do not speak of an animal or a man unless equivocally, as we speak of a painted animal or a stone animal; so is it with the hand, the eye, the flesh and bones …
That it is entire in each part thereof, may be concluded from this, … a whole is that which is divided into parts, [and] there are three kinds of totality, corresponding to three kinds of division. There is a whole which is divided into parts of quantity, as a whole line, or a whole body. There is also a whole which is divided into logical and essential parts: as a thing defined is divided into the parts of a definition …. There is … a third kind of whole which is potential, divided into virtual parts. …
Therefore if it be asked whether the whole whiteness is in the whole surface and in each part thereof, it is necessary to distinguish. If we mean quantitative totality … then the whole whiteness is not in each part of the surface. The same is to be said of totality of power: since the whiteness which is in the whole surface moves the sight more than the whiteness which is in a small part …. But if we mean totality of species and essence, then the whole whiteness is in each part of a surface.
Since, however, the soul has not quantitative totality … the whole soul is in each part of the body, by totality of perfection and of essence, but not by totality of power. For it is not in each part of the body, with regard to each of its powers; but with regard to sight, it is in the eye; and with regard to hearing, it is in the ear; and so forth.”Aquinas, Summa Theologiae, (1266-68) Part 1, Question 76, Article 8. I added the highlighting for emphasis.
Thomas Hobbes was a noted materialist, meaning he thought everything that exists is made of matter and so there are no immaterial souls. Here is how he dismissed Aquinas’s suggestion.
“For the circumscription of a thing, is nothing else but the determination, or defining of its place; and so both the terms of the distinction are the same. And in particular, of the essence of a man, which (they say) is his soul, they affirm it, to be all of it in his little finger, and all of it in every other part (how small soever) of his body; and yet no more soul in the whole body, than in any one of those parts. Can any man think that God is served with such absurdities? And yet all this is necessary to believe, to those that will believe the existence of an incorporeal soul, separated from the body.”Hobbes, Leviathan, (1651) Ch. 46, ¶ 19.
Locke, like Hobbes, rejected Aquinas’s view. However, he did not dismiss it as ridiculous. He just insisted that the person would go along with whatever sustains consciousness. If that is the little finger, then the person would go along with the little finger, even if the immaterial substance remains wholly present in the remaining parts of the body. Locke also rejected Hobbes’s suggestion that a person is just a living material body on similar grounds. If consciousness could be transferred to another body, as in the case of the Prince switching bodies with the Cobbler, then the person would go with it rather than staying with the body.