UNIT 2: EMPIRICISM
HANDOUT 3: LOCKE’S ESSAY, BOOK II CHAPTER XXVII
1: DIFFERENTIATION AND IDENTITY
In chapter XXVII Locke addresses how we derive our ideas of identity and diversity. In other words,
how we come to think that two entities are the same or that two entities are different. There are two
questions regarding identity.
Question 1 (Principle of Differentiation): How can we differentiate one object from
another at any given instant?
Question 2 (Identity over Time): What accounts for the identity of some object over
time?
In other words question 2 fills in the blank of the following sentence.
X at time t1 and Y at a later time t2 are identical if and only if
.
1.1 LOCKE’S PRINCIPLE OF DIFFERENTIATION
Most of Locke’s discussion focuses on Question 2, but he begins with Question 1. Locke argues that
two objects must be different if they cannot occupy the same place at the same time.
When we see anything to be in any place in any instant of time, we are sure (be it
what it will) that it is that very thing, and not another which at that same time exists
in another place, how like and undistinguishable soever it may be in all other
respects: and in this consists identity, when the ideas it is attributed to vary not at all
from what they were that moment wherein we consider their former existence, and
to which we compare the present. For we never finding, nor conceiving it possible,
that two things of the same kind should exist in the same place at the same time, we
rightly conclude, that, whatever exists anywhere at any time, excludes all of the same
kind, and is there itself alone (134).
This leads Locke to posit the following as the “Principum individuationis.”
From what has been said, it is easy to discover what is so much inquired after, the
principium individuationis; and that, it is plain, is existence itself; which determines a
being of any sort to a particular time and place, incommunicable to two beings of the
same kind (135).
1.2 IDENTITY AND KIND
This brings us to the issue of how can something preserve its identity over time. One of Locke’s
most lasting contributions to this question has to do with his idea that identity over time depends
upon what sort of being that thing is. For Locke, the identity of material bodies over time is rather
fluid.
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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. In like manner, if two or more atoms be joined together into the same mass,
every one of those atoms will be the same, by the foregoing rule: and whilst they
exist united together, the mass, consisting of the same atoms, must be the same
mass, or the same body, let the parts be ever so differently jumbled. But if one of
these atoms be taken away, or one new one added, it is no longer the same mass or
the same body (135).
For material bodies, any change in that body will make it such that it is no longer the same thing.
This might seem like a rather strange idea at first. Consider the much discussed ship of Theseus. In
this thought experiment we are to imagine that over time all of the material components of the ship
have been replaced from when it was originally made. This brings up the question of whether the
ship is still the same. Many people’s intuitions are that the same ship does remain, but at first glance
it might seem that Locke’s theory cannot give us that conclusion. This is because there has been
change in the material constitution of the ship.
However, this is not the case. Locke points out that we have to consider what kind, or sort, of thing
we are talking about. Considered as a material body, the ship of Theseus is no longer identical to
what it was before. Yet, considered as a ship (something meant to sail certain routes at sea) it is still
the same ship. This is because it still serves the function that is associated with its kind. Thus, it
depends upon the kind of thing we are talking about. We can see this from Locke’s discussion of the
identity of living creatures.
In the state of living creatures, their identity depends not on a mass of the same
particles, but on something else. For in them the variation of great parcels of matter
alters not the identity: an oak growing from a plant to a great tree, and then lopped,
is still the same oak; and a colt grown up to a horse, sometimes fat, sometimes lean,
is all the while the same horse: though, in both these cases, there may be a manifest
change of the parts; so that truly they are not either of them the same masses of
matter, though they be truly one of them the same oak, and the other the same
horse. The reason whereof is, that, in these two cases a mass of matter and a living
body identity is not applied to the same thing (136).
Locke notes that when an oak tree grows taller, or some of its branches are chopped off, we do not
say that it is a different oak tree. It may be a different material object, but it still serves the same
function of oak tree. Of course, there will be other oak trees that serve that function as well.
However, they are not all the same because (according to Locke’s principle of differentiation) they
cannot occupy the same space at the same time. Locke applies the same sort of analysis to the
identity of non-human animals as well, noting that their identity consists in the organization they
have toward some end (136).
2: IDENTITY OF THE HUMAN ANIMAL
The identity of human beings, however, is more complicated. Locke notes that human beings can be
considered under three different types: substance, man (human animal), and person (137). We can
consider humans as a substance (as either a body or soul), a member of the biological human
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species, and as persons (which as we will see Locke equates with reason and consciousness). Human
identity will differ depending upon what concept we are considering the human being under.
2.1 REJECTING SOUL THEORY
Locke notes that the identity of a human being (the biological species) is determined in the
same way as all other animals.
This also shows wherein the identity of the same man consists; viz. in nothing but a
participation of the same continued life, by constantly fleeting particles of matter, in
succession vitally united to the same organized body (137).
Locke makes clear that in taking this position he is rejecting the soul theory of identity. Soul theory
states the following.
Some human being X at time t1 and some human being Y at a later time t2 are
identical if and only if X and Y share the same soul.
Descartes, for instance, seems to accept this view when he states that what we are is a thinking thing.
Locke does not disagree with this view because he denies the existence of a soul. He just does not
think it explains animal identity very well. This goes back to something we saw him discuss
previously with the possibility of souls moving from one body to another.
For if the identity of soul alone makes the same man; and there be nothing in the
nature of matter why the same individual spirit may not be united to different bodies,
it will be possible that those men, living in distant ages, and of different tempers,
may have been the same man: which way of speaking must be from a very strange
use of the word man, applied to an idea out of which body and shape are excluded.
And that way of speaking would agree yet worse with the notions of those
philosophers who allow of transmigration, and are of opinion that the souls of men
may, for their miscarriages, be detruded into the bodies of beasts, as fit habitations,
with organs suited to the satisfaction of their brutal inclinations. But yet I think
nobody, could he be sure that the soul of Heliogabalus were in one of his hogs,
would yet say that hog were a man or Heliogabalus (137).
If souls can move from one body to another, then people who never shared any of the same
material body could be the same animal. Locke thinks this idea is absurd and therefore rejects the
soul as a criterion of identity of the human animal. Locke notes later, in section 21, that human
identity must consist both of body and soul: “the same immaterial spirit united to the same animal”
(145).
2.2 ANIMAL IDENTITY AND REASON
Thus, animal identity is simply determined by having certain parts that are coordinated to bring
about some end and serve some function. What is important is having our body organized in the
correct way. This implies that reason is not especially important to our human identity.
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Since I think I may be confident, that, whoever should see a creature of his own
shape or make, though it had no more reason all its life than a cat or a parrot, would
call him still a man; or whoever should hear a cat or a parrot discourse, reason, and
philosophize, would call or think it nothing but a cat or a parrot; and say, the one
was a dull irrational man, and the other a very intelligent rational parrot. A relation
we have in an author of great note, is sufficient to countenance the supposition of a
rational parrot (138).
A human who cannot use language or reason is still a human, and a parrot that can do those things
is still a parrot. Each has the correct biological structure of its kind.
3: PERSONAL IDENTITY
However, Locke’s main concern here lies with a different type of identity entirely: personal identity.
What does it mean to say that X at t1 and Y at t2 are the same person?
3.1 LOCKE’S DEFINITION OF PERSON
Understanding personal identity requires first understanding what it means to be a person.
This being premised, to find wherein personal identity consists, we must consider
what person stands for; which, I think, 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; which it does only by that consciousness which is inseparable from
thinking, and, as it seems to me, essential to it: it being impossible for anyone to
perceive without perceiving that he does perceive. When we see, hear, smell, taste,
feel, meditate, or will anything, we know that we do so (138).
Locke states that persons have the following sorts of characteristics.
(i) thought
(ii) intelligence
(iii) reason and reflection
(iv) self awareness of one’s existence over time and place
(v) self awareness of one’s perceptions
Thus, though Locke’s previously described rational parrot is not a human, it does seem that being is
a person.
This has some interesting implications. Consider someone who gets in a car accident and as a result
ends up in a coma. We might ask the question is the person prior to the accident the same as the
person after the accident? Locke would say that it depends upon the manner in which we are
conceiving this person. The person prior to the accident, and following the accident, are the same
human animal. The body is organized in the same way in each case. However, after the accident the
person is like the non rational human that Locke mentions above. Yet, they would not be the same
person. The person in the coma no longer shares the same stream of consciousness with the person
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before the accident, or even has any stream of consciousness. That person does not presently exist
even though their physical body is still technically alive.
3.2 PERSONAL IDENTITY AND MEMORY
For Locke, we know that two persons are identical if they are connected by consciousness. More
specifically, Locke uses a criterion where memory is what is of primary importance.
For, since consciousness always accompanies thinking, and it is that which makes
every one 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 it was
then; and it is by the same self with this present one that now reflects on it, that that
action was done (138).
We can state this more formally as the following.
Some person X at t1 and some person Y at t2 are the same person if and only if Y
remembers being X.
3.3 PERSONAL IDENTITY AND (BODILY/MENTAL) SUBSTANCE
If this is the case, then two people do not have to share the same substance in order to be identical.
This is the case both for material substance (body) and mental substance (soul). Locke first provides
an example involving bodily substance.
Thus, the limbs of his body are to every one a part of Himself; he sympathizes and is
concerned for them. Cut off a hand, and thereby separate it from that consciousness
he had of its heat, cold, and other affections, and it is then no longer a part of that
which is himself, any more than the remotest part of matter. Thus, we see the
substance whereof personal self consisted at one time may be varied at another,
without the change of personal identity; there being no question about the same
person, though the limbs which but now were a part of it, be cut off (139).
3.3.1 TWO SOULS AND ONE PERSON
The same holds for mental substance as well.
But yet, to return to the question before us, it must be allowed, that, if the same
consciousness (which, as has been shown, is quite a different thing from the same
numerical figure or motion in body) can be transferred from one thinking substance
to another, it will be possible that two thinking substances may make but one person.
For the same consciousness being preserved, whether in the same or different
substances, the personal identity is preserved (141).
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Imagine the soul as a kind of container for consciousness. In fact, recall from earlier that Locke
believes the soul is just a passive receptacle. Imagine also two people: person X and person Y.
Person X is conscious and person Y is in a coma (and of course unconscious). All of a sudden X’s
stream of consciousness is removed from X’s soul and placed into Y’s soul causing X to enter a
coma and Y to wake up from a coma. According to Locke, X and Y would have different souls, but
they would be the same person. What is important for personal identity is having psychological
connectedness through memory.
3.3.2 ONE SOUL AND TWO PERSONS
Locke also brings up a case where there could be a single soul but multiple people.
Suppose a Christian Platonist or a Pythagorean should, upon God's having ended all
his works of creation the seventh day, think his soul hath existed ever since; and
should imagine it has revolved in several human bodies […] would anyone say, that
he, being not conscious of any of Socrates's actions or thoughts, could be the same
person with Socrates? Let any one reflect upon himself, and conclude that he has in
himself an immaterial spirit, which is that which thinks in him, and, in the constant
change of his body keeps him the same: and is that which he calls himself: let him
also suppose it to be the same soul that was in Nestor or Thersites, at the siege of
Troy, (for souls being, as far as we know anything of them, in their nature indifferent
to any parcel of matter, the supposition has no apparent absurdity in it), which it may
have been, as well as it is now the soul of any other man: but he now having no
consciousness of any of the actions either of Nestor or Thersites, does or can he
conceive himself the same person with either of them? Can he be concerned in
either of their actions? attribute them to himself, or think them his own, more than
the actions of any other men that ever existed? […] For this would no more make
him the same person with Nestor, than if some of the particles of matter that were
once a part of Nestor were now a part of this man; the same immaterial substance,
without the same consciousness, no more making the same person, by being united
to anybody, than the same particle of matter, without consciousness, united to
anybody, makes the same person. But let him once find himself conscious of any of
the actions of Nestor, he then finds himself the same person with Nestor (141-142).
If in a past life, for instance, Ryan’s soul was in the body of Socrates, this does not mean that Ryan is
the same person as Socrates. This is because Ryan cannot remember anything about Socrates or
share any stream of consciousness with him.
We can imagine a similar case with someone who has Dissociative Identity Disorder (formerly
Multiple Personality Disorder). This is described in the Diagnostic and Statistical Manual of Mental
Disorders (4th edition) as the following.
Dissociative Identity Disorder reflects a failure to integrate various aspects of
identity, memory, and consciousness. Each personality state may be as if it has a
distinct personal history, self-image, and identity, including a separate name.1
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Diagnostic and Statistical Manual of Mental Disorders, 4th edition, 526.
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If this person has two streams of consciousness, each of which has no recollection of the other, then
there would be (for Locke) two persons sharing one mental substance. Thus, the soul is not primary
for Locke when determining personal identity.
We should already be familiar with this idea from Locke’s Castor and Pollux example in Part I. He
also provides a very similar example of the day man and the night man on pg. 146.
3.4 RESURRECTION AND THE BODY
Locke also believes that his account of personal identity can provide an explanation of certain
problems that arose at the time for thinking about life after death.2 According to the Bible in the
afterlife we will have the same body as we had when we were on Earth. One of Locke’s
contemporaries, Robert Boyle, noted that this brings up a number of problematic issues.
When a man is once really dead, divers of the parts of his body will, according to the
course of nature, resolve themselves into multitudes of steams that wander to and
fro in the air; and the remaining parts, that are either liquid or soft, undergo so great
a corruption and change, that it is not possible so many scattered parts should be
again brought together, and reunited after the same manner, wherein the existed in a
human body whilst it was yet alive. And much more impossible it is to effect this
reunion, if the body have been, as it often happens, devoured by wild beasts or
fishes; since in this case, though the scattered parts of the cadaver might be
recovered as particles of matter, yet already having passed into the substance of other
animals, they are quite transmuted, as being informed by the new form of the beast
or fish that devoured them and of which they now make a substantial part.3
It is unclear how our body is supposed to be reassembled in the afterlife. The problem is even more
pressing when we think of those who die as a result of being eaten by cannibals.
And yet far more impossible will this reintegration be, if we put the case that the
dead man was devoured by cannibals; for then, the same flesh belonging successively
to two different persons, it is impossible that both should have it restored to them at
once, or that any footsteps should remain of the relation it had to the first
possessor.4
How can one’s body reappear in heaven when it has combined with the body of another person?
Locke believes that his theory can make sense of this issue by stressing that bodily continuity is not
the most important aspect of personal identity.
The body, as well as the soul, goes to the making of a man. And thus may we be
able, without any difficulty, to conceive the same person at the resurrection, though
in a body not exactly in make or parts the same which he had here,- the same
See Stanford Encyclopedia of Philosophy Entry, Personal Identity and the Immateriality of the Soul, Supplement to
John Locke, on this point (link).
3 Robert Boyle, Selected Philosophical Papers of Robert Boyle, ed. M.A. Stewart, Manchester University Press, New York, 1979.
198.
4 Ibid., 198.
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consciousness going along with the soul that inhabits it. But yet the soul alone, in the
change of bodies, would scarce to anyone but to him that makes the soul the man,
be enough to make the same man (142).
He argues for this with an example of a prince and a cobbler.
For should the soul of a prince, carrying with it the consciousness of the prince's
past life, enter and inform the body of a cobbler, as soon as deserted by his own
soul, everyone sees he would be the same person with the prince, accountable only
for the prince's actions: but who would say it was the same man? The body too goes
to the making the man, and would, I guess, to everybody determine the man in this
case, wherein the soul, with all its princely thoughts about it, would not make
another man: but he would be the same cobbler to everyone besides himself (142).
If the souls of the prince and the cobbler were switched, then according to Locke’s view the prince
would be waking up in the cobbler’s body and the cobbler would be waking up in the prince’s body.
However, because there has been such radical change in the composition of each entity, neither
would be the same “man” they were before. Thus, the fact that the being in heaven does not have
the same sort of bodily organization as the person who lived on earth does not mean that we cannot
survive our deaths. All that matters is that our stream of consciousness continues in the afterlife.
4: PERSONAL IDENTITY AND MORAL/LEGAL RESPONSIBILITY
One of advantages Locke thinks it has is that it explains our views about moral responsibility,
reward, and punishment.
In this personal identity is founded all the right and justice of reward and
punishment; happiness and misery being that for which everyone is concerned for
himself, and not mattering what becomes of any substance, not joined to, or affected
with that consciousness (144).
Recall the example we looked at earlier when discussing Leibniz. Imagine Bob1 committed a murder.
When the police eventually arrest someone for the crime they will not be arresting Bob1, but instead
will arrest Bob2. How is this fair? It only seems fair if Bob1 and Bob2 are the same person. Locke
thinks that when we accuse someone of a crime we only feel we are identifying the right person if
that person can remember doing the crime; namely, if Bob2 remembered committing the crime of
Bob1.
4.1 RESPONSIBILITY AND FORGETTING OUR WRONGS
Consider the following example.
This may show us wherein personal identity consists: not in the identity of substance,
but, as I have said, in the identity of consciousness, wherein if Socrates and the
present mayor of Quinborough agree, they are the same person: if the same Socrates
waking and sleeping do not partake of the same consciousness, Socrates waking and
sleeping is not the same person. And to punish Socrates waking for what sleeping
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Socrates thought, and waking Socrates was never conscious of, would be no more of
right, than to punish one twin for what his brother-twin did, whereof he knew
nothing, because their outsides were so like, that they could not be distinguished; for
such twins have been seen (144).
If Socrates committed a crime while he was sleep walking, it would be wrong (in Locke’s view) to
punish Awake Socrates for that crime if Awake Socrates had no recollection of doing it. Locke notes
that some will object that even if we forget what we did in the past, we were still the one’s who
performed those actions. Locke again appeals to the distinction between man and person.
But yet possibly it will still be objected, Suppose I wholly lose the memory of some
parts of my life, beyond a possibility of retrieving them, so that perhaps I shall never
be conscious of them again; yet am I not the same person that did those actions, had
those thoughts that I once was conscious of, though I have now forgot them? To
which I answer, that we must here take notice what the word I is applied to; which,
in this case, is the man only. And the same man being presumed to be the same
person, I is easily here supposed to stand also for the same person. But if it be
possible for the same man to have distinct incommunicable consciousness at
different times, it is past doubt the same man would at different times make different
persons; which, we see, is the sense of mankind in the solemnest declaration of their
opinions, human laws not punishing the mad man for the sober man's actions, nor
the sober man for what the mad man did, thereby making them two persons: which
is somewhat explained by our way of speaking in English when we say such an one is
"not himself," or is "beside himself"; in which phrases it is insinuated, as if those
who now, or at least first used them, thought that self was changed; the selfsame
person was no longer in that man (144-145).
Imagine someone who committed a crime while blacked out drunk, and then had no recollection of
it the next morning. Locke admits it was the same “man” who did the crime; however, it is not the
same person. Therefore, the sober person is not technically responsible for the crime. Dissociative
Personal Disorder is again relevant here.
4.2 PRACTICAL REASONS FOR LEGAL PUNISHMENT
The sober man is not genuinely responsible for the madman’s actions because the sober man and
the madman are not the same person (even if they are the same man). However, Locke admits that
we might still have some practical reasons to punish the sober man for the madman’s misdeeds.
Human laws punish both, with a justice suitable to their way of knowledge;- because,
in these cases, they cannot distinguish certainly what is real, what counterfeit: and so
the ignorance in drunkenness or sleep is not admitted as a plea. For, though
punishment be annexed to personality, and personality to consciousness, and the
drunkard perhaps be not conscious of what he did, yet human judicatures justly
punish him; because the fact is proved against him, but want of consciousness
cannot be proved for him. But in the Great Day, wherein the secrets of all hearts
shall be laid open, it may be reasonable to think, no one shall be made to answer for
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what he knows nothing of, but shall receive his doom, his conscience accusing or
excusing him (146).
We are still justified in punishing the sober man, because our knowledge is limited. As a practical
matter, it would be impossible to determine in every case whether someone really committed a crime
or not. If this seems wrong, Locke tries to comfort us by appealing to divine justice. God would
only punish the madman’s stream of consciousness, but not the sober man’s stream of
consciousness.
4.3 “PERSON” IS A FORENSIC TERM
From this Locke draws a conclusion about the purpose of denominating someone a person.
"Person" a forensic term. Person, as I take it, is the name for this self. Wherever a
man finds what he calls himself, there, I think, another may say is the same person. 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. This personality
extends itself beyond present existence to what is past, only by consciousness,whereby it becomes concerned and accountable; owns and imputes to itself past
actions, just upon the same ground and for the same reason as it does the present.
All which is founded in a concern for happiness, the unavoidable concomitant of
consciousness; that which is conscious of pleasure and pain, desiring that that self
that is conscious should be happy. And therefore whatever past actions it cannot
reconcile or appropriate to that present self by consciousness, it can be no more
concerned in than if they had never been done: and to receive pleasure or pain, i.e.
reward or punishment, on the account of any such action, is all one as to be made
happy or miserable in its first being, without any demerit at all (148).
Person is a forensic term, meaning its entire purpose is to allow us to denominate people as
responsible for what they have done and worthy of praise, blame, reward, and punishment.
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