Another context in which the mind compares things [= ‘considers things together’] is their very being: when we consider something as existing at a given time and place and compare it with itself existing at another time, we are led to form the ideas of identity and diversity. [In this context ‘diversity’ means ‘nonidentity.’ To say that x is diverse from y is to say only that x is not y.] When we see a thing—anything, of whatever sort—to be in a certain place at a certain time, we are sure that it is that very thing and not another thing existing at that time in some other place, however alike the two may be in all other respects. And in this consists identity, when the ideas to which it is attributed do not vary from what they were at the moment of their former existence that we are comparing with the present. We never find—and cannot even conceive of—two things of the same kind existing in the same place at the same time, so we rightly conclude that whatever exists in a certain place at a certain time excludes all others of the same kind, and is there itself alone. So, when we ask whether a thing is ‘the same’ or not, we are always referring to something that existed at a given time in a given place, a thing that at that instant was certainly the same as itself and not the same as anything else. From this it follows that

• one thing cannot have two beginnings of existence because it is impossible for one thing to be in different places at the same time and
• two things cannot have one beginning, because it is impossible for two things of the same kind to exist in the same instant at the very same place.

Thus, what had one beginning is the same thing; and what had a different beginning in time and place from that is not the same but diverse. The difficulties philosophers have had with this relation of identity have arisen from their not attending carefully to the precise notions of the things to which it is attributed.

We have ideas of only three sorts of substances: God, finite intelligences, and bodies.

1. God is without beginning, eternal, unalterable, and everywhere; and so there can be no doubt concerning his identity.
2. Each finite spirit had its determinate time and place of beginning to exist, so its relation to that time and place will always determine its identity for as long as it exists.
3. The same holds for every particle of matter, which continues as the same as long as no matter is added to or removed from it. . ..

These three sorts of ‘substances’ (as we call them) don’t exclude one another out of the same place, but we can’t conceive any of them allowing another of the same kind into its place. If that were to happen, the notions and names of identity and diversity would be useless, and there would be no way of distinguishing substances or anything else from one another. For example: if two bodies could be in the same place at the same time, then those two portions of matter would be one and the same, whatever their size. Indeed, all bodies would be one and the same, because allowing two bodies to be in one place at one time allows for all bodies to do so. To suppose this to be possible is to obliterate the distinction between identity and diversity, the difference between one and more….

That all concerned the identity of substances. There remain modes and relations, but because they ultimately depend on substances [Locke says they are ‘ultimately terminated in substances’], the identity and diversity of each particular one of them will be determined in the same way as the identity of particular substances. Questions of identity and diversity do not arise for things whose existence consists in a sequence of events such as the actions of finite beings, e.g. motion and thought. Because each of these events perishes the moment it begins, they cannot exist at different times or in different places, as enduring things can; and therefore, no motion or thought can be the same as any earlier motion or thought.

There has been much inquiry after the principle of individuation; but what I have said enables us easily to discover what that is: it is existence itself, which ties a being of a given sort to a particular time and place that cannot be shared by any other being of the same kind. This seems easier to conceive in simple substances or modes, but if we are careful we can just as easily apply it to compound ones. Consider an atom, i.e. a continued body under one unchanging surface, existing at a particular time and place: it is evident that at that instant it is the same as itself. For being at that instant what it is and nothing else, it is the same and so must continue as long as its existence is continued; for so long it will be the same and no other. [That sentence is Locke’s.] Similarly, if two or more atoms are joined together into a single mass, every one of those atoms will be the same by the foregoing rule. And while they exist united together, the mass whose parts they are must be the same mass, or the same body, however much the parts have been re arranged. But if one atom is removed from the mass, or one new one added, it is no longer the same mass, or the same body. The identity of living creatures depends not on a mass of the same particles but on something else. For in them the variation of large amounts of matter does not alter the identity. An oak growing from a sapling to a great tree, and then lopped, is still the same oak; and a colt grown up to be a horse, sometimes fat, sometimes lean, is the same horse throughout all this. In neither case is there the same mass of matter, though there truly is the same oak, or horse. That is because in these two cases, a mass of matter and a living body, identity is not applied to the same thing.

How, then, does an oak differ from a mass of matter? The answer seems to me to be this: the mass is merely the cohesion of particles of matter anyhow united, whereas the oak is such a disposition of particles as constitutes the parts of an oak, and an organization of those parts that enables the whole to receive and distribute nourishment so as to continue and form the wood, bark, and leaves, etc. of an oak, in which consists the vegetable life. Thus, something is one plant if it has an organization of parts in one cohering body partaking of one common life, and it continues to be the same plant as long as it partakes of the same life, even if that life is passed along to new particles of matter vitally united to the living plant, in a similar continued organization suitable for that sort of plants. This organization is at any one instant in some one collection of matter, which distinguishes it from all others at that instant; and what has the identity that makes the same plant is that individual life, existing constantly from that moment forwards and backwards, in the same continuity of imperceptibly succeeding parts united to the living body of the plant. It also makes all the parts of it be parts of the same plant, for as long as they exist united in that continued organization that is fit to convey that common life to all the parts so united.

The identity of lower animals is sufficiently like that for anyone to be able to see, from what I have said, what makes one animal and continues it the same. It can be illustrated by something similar, namely the identity of machines. What is a watch? Clearly it is nothing, but a construction of parts organized to a certain end—an end that it can attain when sufficient force is applied to it. If we suppose this machine to be one continued body whose parts were repaired, added to, or subtracted from, by a constant addition or separation of imperceptible parts, with one common life, it would be very much like the body of an animal; with the difference that in an animal the fitness of the organization and the motion wherein life consists begin together, because the motion comes from within; but in a machine the force can be seen to come from outside, and is often lacking even when the machine is in order and well fitted to receive it— for example, when a clock isn’t wound up.

This also shows what the identity of the same man consists in, namely: a participation in the same continued life by constantly fleeting particles of matter that are successively vitally united to the same organized body. If you place the identity of man in anything but this, you will find it hard to make an embryo and an adult the same man, or a well man and a madman the same man.

Your only chance of doing this is by tying ‘same man’ to ‘same soul,’ but by that standard you will make it possible for Seth, Ismael, Socrates, Pilate, St. Augustine, and Cesare Borgia to be the same man. If identity of soul alone makes the same man, and nothing in the nature of matter rules out an individual spirit’s being united to different bodies, it will be possible that those men with their different characters and living at widely different times, may have been the same man! That strange way of using the word ‘man’ is what one is led to by giving it a meaning from which body and shape are excluded. …

So unity of substance does not constitute all sorts of identity. To conceive and judge correctly about identity, we must consider what idea the word it is applied to stands for: it is one thing to be the same substance, another the same man, and a third the same person, if ‘person’, ‘man’, and ‘substance’ are names for three different ideas; for such as is the idea belonging to that name, such must be the identity. If this had been more carefully attended to, it might have prevented a great deal of that confusion that often occurs regarding identity, and especially personal identity, to which I now turn after one more section on ‘same man.’

An animal is a living organized body; and consequently, the same animal, as I have said, is the same continued life communicated to different particles of matter, as they are successively united to that organized living body. And whatever other definitions are propounded, there should be no doubt that the word ‘man’ as we use it stands for the idea of an animal of a certain form. The time hallowed definition of ‘man’ as ‘rational animal’ is wrong.

If we should see a creature of our own shape and physical constitution, though it had no more reason all its life than a cat or a parrot, we would still call him a man; and anyone who heard a cat or a parrot talk, reason, and philosophize would still think it to be a cat or a parrot and would describe it as such. One of these two is

• a dull, irrational man, the other
• a very intelligent rational parrot.

[Locke then quotes a tediously long traveler’s tale about encountering a rational parrot. His point is that someone who believes this account will go thinking of this rational animal as a parrot, not as a man.]

With ‘same man’ in hand, let us turn to ‘same person’. To find what personal identity consists in, we must consider what ‘person’ stands for.

I think it is a thinking intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing at different times and places. What enables it to think of itself is its consciousness, which is inseparable from thinking and (it seems to me) essential to it.

It is impossible for anyone to perceive, without perceiving that he perceives. When we see, hear, smell, taste, feel, meditate, or will anything, we know that we do so. It is always like that with our present sensations and perceptions. And it is through this that everyone is to himself that which he calls ‘self, not raising the question of whether the same self is continued in the same substance.

Consciousness always accompanies thinking, and makes everyone to be what he calls ‘self’ and thereby distinguishes himself from all other thinking things; in this alone consists personal identity, i.e. the sameness of a rational being; and as far as this consciousness can be extended backwards to any past action or thought, so far reaches the identity of that person; it is the same self now that it was then; and this present self that now reflects on it is the one by which that action was performed.

Given that it is the same person, is it the same identical substance? Most people would think that it is the same substance if these perceptions with their consciousness always remained present in the mind, making the same thinking thing always consciously present and (most people would think) evidently the same to itself. What seems to make the difficulty— that is, to make it at least questionable whether the same person must be the same substance— is the following fact.

Consciousness is often interrupted by forgetfulness, and at no moment of our lives do we have the whole sequence of all our past actions before our eyes in one view; even the best memories lose the sight of one part while they are viewing another.

Furthermore, for the greatest part of our lives we don’t reflect on our past selves at all, because we are intent on our present thoughts or (in sound sleep) have no thoughts at all, or at least none with the consciousness that characterizes our waking thoughts. In all these cases our consciousness is interrupted, and we lose the sight of our past selves, and so doubts are raised as to whether or not we are the same thinking thing, i.e. the same substance.

That may be a reasonable question, but it has nothing to do with personal identity. For the latter, the question is about what makes the same person, and not whether the same identical substance always thinks in the same person. Different substances might all partake in a single consciousness and thereby be united into one person, just as different bodies can enter into the same life and thereby be united into one animal, whose identity is preserved throughout that change of substances by the unity of the single continued life. What makes a man be himself to himself is sameness of consciousness, so personal identity depends entirely on that—whether the consciousness is tied to one substance throughout or rather is continued in a series of different substances. For as far as any thinking being can repeat the idea of any past action with the same consciousness that he had of it at first, and with the same consciousness he has of his present actions, so far is he the same personal self. For it is by the consciousness he has of his present thoughts and actions that he is self to himself now, and so will be the same self as far as the same consciousness can extend to actions past or to come. Distance of time doesn’t make him two or more persons, and nor does change of substance; any more than a man is made to be two men by having a long or short sleep or by changing his clothes.

Our own bodies give us some kind of evidence for this. All the particles of your body, while they are vitally united to a single thinking conscious self—so that you feel when they are touched, and are affected by and conscious of good or harm that happens to them—are a part of yourself, i.e. of your thinking conscious self. Thus, the limbs of his body are to everyone a part of himself; he feels for them and is concerned for them. Cut off a hand and thereby separate it from that consciousness the person had of its heat, cold, and other states, and it is then no longer a part of himself, any more than is the remotest material thing. Thus, we see the substance of which the personal self consisted at one time may be varied at another without change of personal identity; for there is no doubt that it is the same person, even though one of its limbs has been cut off.

But it is asked: Can it be the same person if the substance changes? and Can it be different persons if the same substance does the thinking throughout?

Before I address these questions in sections 13 and 14, there’s a preliminary point I want to make. It is that neither question is alive for those who hold that thought is a property of a purely material animal constitution, with no immaterial substance being involved. Whether or not they are right about that, they obviously conceive personal identity as being preserved in something other than identity of substance; just as animal identity is preserved in identity of life, not of substance. This pair of questions does present a challenge to those who hold that only immaterial substances can think, and that sameness of person requires sameness of immaterial substance.

Before they can confront their materialist opponents, they have to show why personal identity can’t be preserved through a change of immaterial substances, just as animal identity is preserved through a change of material substances. Unless they say that what makes the same life and thus the animal identity in lower animals is one immaterial spirit, just as (according to them) one immaterial spirit makes the same person in men—and Cartesians at least won’t take that way out, for fear of making the lower animals thinking things too.

As to the first question, If the thinking substance is changed, can it be the same person? I answer that this can be settled only by those who know what kind of substances they are that think, and whether the consciousness of past actions can be transferred from one such substance to another.

Admittedly, if the same consciousness were the same individual action, it couldn’t be transferred because in that case bringing a past headache (say) into one’s consciousness would be bringing back that very headache, and that is tied to the substance to which it occurred. But a present consciousness of a past event isn’t like that. Rather it is a present representation of a past action, and we have still to be shown why something can’t be represented to the mind as having happened though really it did not. How far the consciousness of past actions is tied to one individual agent, so that another can’t possibly have it, will be hard for us to determine until we know what kind of action it is that can’t be done without a reflex act of perception accompanying it, and how such an action is done by thinking substances who can’t think without being conscious of it. In our present state of knowledge, it is hard to see how it can be impossible, in the nature of things, for an intellectual substance to have represented to it as done by itself something that it never did, and was perhaps done by some other agent…. Until we have a clearer view of the nature of thinking substances, we had better assume that such changes of substance within a single person never do in fact happen, basing this on the goodness of God. Having a concern for the happiness or misery of his creatures, he won’t transfer from one substance to another the consciousness that draws reward or punishment with it. …

The second question, Can it be different persons if the same substance does the thinking throughout? seems to me to arise out of the question of whether the following is possible:

An immaterial being that has been conscious of the events in its past is wholly stripped of all that consciousness, losing it beyond the power of ever retrieving it again; so that now it (as it were) opens a new account, with a new starting date, having a consciousness that can’t reach back beyond this new state.

Really, the question is whether if this happened it could be the same person who had first one consciousness and then another, with no possibility of communication between them. [Locke says that this must be regarded as possible by ‘those who hold preexistence’, that is, who believe in reincarnation. He attacks them, thereby attacking the separation of ‘same person’ from ‘same consciousness’, and proposes a thought experiment:] Reflect on yourself, and conclude that you have in yourself an immaterial spirit that is what thinks in you, keeps you the same throughout the constant change of your body, and is what you call ‘myself’. Now try to suppose also that it is the same soul that was in Nestor or Thersites at the siege of Troy. This isn’t obviously absurd; for souls, as far as we know anything of their nature, can go with any portion of matter as well as with any other; so the soul or thinking substance that is now yourself may once really have been the soul of someone else, such as Thersites or Nestor. But you don’t now have any consciousness of any of the actions either of those two; so can you conceive yourself as being the same person with either of them? Can their actions have anything to do with you? Can you attribute those actions to yourself, or think of them as yours more than the actions of any other men that ever existed? Of course you can’t ….

So we can easily conceive of being the same person at the resurrection, though in a body with partly different parts or structure from what one has now, as long as the same consciousness stays with the soul that inhabits the body. But the soul alone, in the change of bodies, would not be accounted enough to make the same man—except by someone who identifies the soul with the man. If the soul of a prince, carrying with it the consciousness of the prince’s past life, were to enter and inform the body of a cobbler who has been deserted by his own soul, everyone sees that he would be the same person as the prince, accountable only for the prince’s actions; but who would say it was the same man? The body contributes to making the man, and in this case, I should think everyone would let the body settle the ‘same man’ question, not dissuaded from this by the soul, with all its princely thoughts. To everyone but himself he would be the same cobbler, the same man. I know that in common parlance ‘same person’ and ‘same man’ stand for the same thing; and of course everyone will always be free to speak as he pleases, giving words what meanings he thinks fit, and changing them as often as he likes. Still, when we want to explore what makes the same spirit, man, or person, we must fix the ideas of spirit, man, or person in our minds; and when we have become clear about what we mean by them, we shan’t find it hard to settle, for each of them, when it is ‘the same’ and when not.

But although the same immaterial substance or soul does not by itself, in all circumstances, make the same man, it is clear that consciousness unites actions—whether from long ago or from the immediately preceding moment—into the same person. Whatever has the consciousness of present and past actions is the same person to whom they both belong. If my present consciousness that I am now writing were also a consciousness that I saw an overflowing of the Thames last winter and that I saw Noah’s ark and the flood, I couldn’t doubt that I who write this now am the same self that saw the Thames overflowed last winter and viewed the flood at the general deluge—place that self in what substance you please. I could no more doubt this than I can doubt that I who write this am the same myself now while I write as I was yesterday, whether or not I consist of all the same substance, material or immaterial. For sameness of substance is irrelevant to sameness of self: I am as much involved in—and as justly accountable for— an action that was done a thousand years ago and is appropriated to me now by this self-consciousness as I am for what I did a moment ago.

Self is that conscious thinking thing that feels or is conscious of pleasure and pain and capable of happiness or misery, and so is concerned for itself as far as that consciousness extends. (This holds true whatever substance the thinking thing is made up of; it doesn’t matter whether it is spiritual or material, simple or compounded.) You must find that while your little finger is brought under your consciousness it is as much a part of yourself as is your head or your heart. If the finger were amputated and this consciousness went along with it, deserting the rest of the body, it is evident that the little finger would then be the person, the same person; and this self would then would have nothing to do with the rest of the body. As with spatial separation so also with temporal: something with which the consciousness of this present thinking thing can join itself makes the same person, and is one self with it, as everyone who reflects will perceive.

Personal identity is the basis for all the right and justice of reward and punishment. What everyone is concerned for, for himself, is happiness and misery—with no concern for what becomes of any substance that isn’t connected with that consciousness. [Locke goes on to apply that to his ‘finger’ example, supposing that the finger takes the original consciousness with it, and that the rest of the body acquires a new consciousness.]

This illustrates my thesis that personal identity consists not in the identity of substance but in the identity of consciousness. If Socrates and the present mayor of Queenborough agree in that, they are the same person; if Socrates awake doesn’t partake of the same consciousness as Socrates sleeping, they aren’t the same person. And to punish Socrates awake for something done by sleeping Socrates without Socrates awake ever being conscious of it would be as unjust as to punish someone for an action of his twin brother’s merely because their outsides were so alike that they couldn’t be distinguished.

It may be objected: ‘Suppose I wholly lose the memory of some parts of my life beyond any possibility of retrieving them, so that I shall never be conscious of them again; aren’t I still the same person who did those actions, had those thoughts that I once was conscious of, even though I have now forgotten them?’ To this I answer that we must be careful about what the word ‘I’ is applied to. This objector is thinking of sameness of the man, and calls it ‘I’ because he assumes that the same man is the same person. But the assumption isn’t necessarily correct . If one man could have distinct disconnected consciousnesses at different times, that same man would certainly make different persons at different times. That this is what people in general think can be seen in the most solemn declaration of their opinions: human laws don’t punish the madman for the sane man’s actions, or the sane man for what the madman did, because they treat them as two persons. This is reflected in common speech when we say that someone is ‘not himself or is ‘beside himself’. Those phrases insinuate that the speaker thinks—or that those who coined the phrases thought—that the self was changed, the self-same person was no longer in that man.

‘It is still hard to conceive that Socrates, the same individual man, might be two persons.’ To help us with this we must consider what is meant by ‘Socrates’, or ‘the same individual man’. There are three options . The same man might be any of these:

• the same individual, immaterial, thinking substance; in short, the numerically same soul and nothing else,
• the same animal, without any regard to an immaterial soul,
• the same immaterial spirit united to the same animal.

Help yourself! On any of these accounts of ‘same man’, it is impossible for personal identity to consist in anything but consciousness, or reach any further than that does. According to 1, a man born of different women, and in distant times, might still be the same man. Anyone who allows this must also allow that the same man could be two distinct persons. . . . According to 2 and 3, Socrates in this life cannot be the same man as anyone in the afterlife. The only way to do this— allowing for the possibility that Socrates in Athens and Socrates in Limbo are the same man— is through an appeal to sameness of consciousness; and that amounts to equating human identity— ‘same man’— with personal identity. But that equation is problematic, because it makes it hard to see how the infant Socrates can be the same man as Socrates after the resurrection. There seems to be little agreement about what makes a man, and thus about what makes the same individual man; but whatever we think about that, if we are not to fall into great absurdities we must agree that sameness of person resides in consciousness.

You may want to object: ‘But isn’t a man drunk and sober the same person? Why else is he punished for what he does when drunk, even if he is never afterwards conscious of it? He is just as much a single person as a man who walks in his sleep and is answerable, while awake, for any harm he did in his sleep.’ Here is my reply to that . Human laws punish both, with a justice suitable to the state of knowledge of those who administer the law: in these cases they can’t distinguish for sure what is real from what is counterfeit; and so they don’t allow the ignorance in drunkenness or sleep as a plea. Granted: punishment is tied to personhood, which is tied to consciousness, and the drunkard may not be conscious of what he did; but the courts justly punish him, because his bad actions are proved against him, and his lack of consciousness of them can’t be proved for him. It may be reasonable to think that on the great day when the secrets of all hearts are laid open, nobody will be held accountable for actions of which he knows nothing; everybody will receive his sentence with his conscience agreeing with God’s judgment by accusing or excusing him.

Nothing but consciousness can unite remote existences into the same person. The identity of substance won’t do it. For whatever substance there is, and whatever it is like, without consciousness there is no person. A substance without consciousness can no more be a person that a carcass can.

[In the remainder of this section, and in section 24. Locke discusses possible cases: two persons who take turns in animating one animal body (‘the night man and the day man’); and one person who alternately animates two different animal bodies. The central emphasis throughout is on the uselessness in these questions of the concept of the same immaterial substance.]

I agree that on the question of contingent fact the more probable opinion is that this consciousness is tied to, and is a state of, a single immaterial substance. Please yourself about that. However, every thinking being that can experience happiness or misery must grant that there is something, himself, that he is concerned for and wants to be happy; and that this self has existed continuously for a period of time and therefore may exist for months and years to come, with no set limit to its duration, and thus may be the same self, carried by consciousness into the future. It is through this consciousness that he finds himself to be the same self that acted thus and so some years ago and through which he is happy or miserable now. In all these thoughts we place sameness of self in sameness not of substance but of consciousness. Substances might come and go through the duration of such a consciousness; and for as long as a substance is in a vital union with the thing containing this consciousness it is a part of that same self. Thus, any part of my body, while vitally united to that which is conscious in me, is a part of myself ( for example my little finger, while it relates to me in such a way that if it is damaged I feel pain ); but when the vital union is broken, what was a part of myself a moment ago is now not so, any more than a part of another man’s self is a part of me. [The rest of the section illustrates and repeats this line of thought.]

‘Person’, I take it, is the name for this self. Wherever you find what you call ‘myself, anyone else may say there is ‘the same person’. ‘Person’ is a forensic term [= ‘a term designed for use in legal proceedings’], having to do with actions and their merit; and so it applies only to active thinking beings that are capable of a law, and of happiness and misery. It is only through consciousness that this personality [Locke’s word] extends itself beyond present existence to what is past, becoming concerned and accountable; the person owns and attributes past actions to itself for the same reason that it does the present. All this is founded in a concern for happiness, which unavoidably accompanies consciousness— something that is conscious of pleasure and pain desires that the self that is conscious should be happy. As for past actions that the self cannot through consciousness square with or join to the present self—it can no more be concerned with them than if they had never been done. To receive pleasure or pain, i.e. reward or punishment, on account of any such action is all of a piece with being born happy or miserable, without any merit or demerit at all. Suppose a man were punished now for what he had done in another life of which he cannot have any consciousness, how does that so-called punishment differ from simply being created miserable?

In treating this subject I have considered as perhaps possible some states of affairs— e.g. the one about the prince and the cobbler— that will look strange to some readers, and perhaps are strange. But I think they are permissible, given our ignorance about the nature of the thinking thing in us which we look on as ourselves. If we knew with regard to this thinking thing what it is, or how it is tied to a certain system of fleeting animal spirits [see note in viii.12], or whether or not it can perform its operations of thinking and memory outside of a body organized as ours is, and whether God has decided that every such spirit or thinking thing shall be united to only one such body, with its memory depending on the health of that body’s organs, we might see the absurdity of some of the cases I considered. But as we are in the dark about these matters, we ordinarily think of the thinking thing or soul of a man as an immaterial substance, owing nothing to matter and compatible with any kind of matter; and on that basis there cannot from the nature of things be any absurdity in supposing that the same soul might at different times be united to different bodies, making one man with each of them for as long as they were united….

To conclude: any substance that begins to exist must during its existence necessarily be the same; any complex of substances that begins to exist must during the existence of its component parts be the same; any mode that begins to exist is throughout its existence the same. . . . It appears from this that the difficulty or obscurity that people have found in this matter has arisen from the poor use of words rather than from any obscurity in things themselves. For whatever makes the specific idea to which the name is applied, if we steadily keep to that idea it will be easy for us to distinguish same and different, with no doubts arising. I defend this in the next, final section .

Suppose we take a man to be a rational spirit, then it is easy to know what is the same man, namely the same spirit—whether or not it is embodied. Suppose our idea of a man is a rational spirit vitally united to a body with a certain structure; then such a rational spirit will be the same man as long as it is united to such a body, though it needn’t be the same body throughout. If anyone’s idea of a man is that of the vital union of parts in a certain shape [here = ‘structure’], as long as that vital union and shape remain in a compound body, remaining the same except for a turnover in its constituent particles, it will be the same man. For the complex idea we use when classifying a thing as being of a certain kind also determines what it is for a thing of that kind to continue in existence.