In Search of the Simple View
Eric T. Olson
In G. Gasser and M. Stefan, eds., Personal Identity: Complex or Simple?
Cambridge University Press 2012
abstract
Accounts of personal identity over time are supposed to fall into two broad
categories: complex views saying that our persistence consists in something else,
and simple views saying that it doesn t. But it is impossible to characterize this
distinction in any satisfactory way. The debate has been systematically
misdescribed. After arguing for this claim, the paper says something about how the
debate might be better characterized.
1. Simple and complex views
We tell our students that accounts of personal identity over time fall into two
broad categories. First there are complex views according to which personal
identity consists in something else: when there is a fact about our identity or
nonidentity, there is some other, deeper fact that underlies and is responsible for it.
There are familiar debates about what these deeper facts are--whether they have to
do entirely with brute physical continuity, for example, or with some sort of
psychological continuity, perhaps with a physical constraint. The second category,
the simple view, rejects all this, and denies that our persistence or identity over
time consists in anything. A certain past or future being is or isn t you, and that s all
there is to be said. Nothing further makes it you or not you. The identity or
nonidentity of an earlier person and a later one is already as deep as it gets. The
taxonomy looks like this:
Advocates of simple and complex views are supposed to disagree about
something more fundamental than those who differ over what personal identity
consists in, namely about whether it consists in anything at all. And because the
1
simple view just denies what complex views assert, the two categories must be
both exclusive and exhaustive: any account of personal identity over time must be
either simple or complex and not both.
If this is right, it ought to be possible to say what the two sides disagree about.
What proposition is it that friends of complex views accept and friends of the simple
view deny? What do you have to believe in order to accept a complex view, and
what belief (or lack of belief) characterizes the simple view? This question is
surprisingly hard to answer. The trouble is not merely that there are hard cases-views of personal identity that resist classification as either simple or complex--but
that no answer even gets all the easy cases right. And those proposals that best
approximate the traditional boundary between simple and complex lack the interest
and importance that the boundary is thought to have. If there is such a doctrine as
the simple view, it s certainly not what we thought it was. The personal-identity
debate has been systematically misdescribed. After explaining why I believe this, I
will say something about how the debate might be better characterized.
2. Preliminaries
First some brief points of clarification.
There are three assumptions commonly taken for granted in discussions of
personal identity that I am not going to make, rendering some of my formulations
unusual. One is that if the identity over time of any person consists in something,
then necessarily the identity of every person consists in something. A second is
that the identity of all people whose identity consists in anything must consist in the
same thing. I want to leave open the possibility that our own identity consists in
something but the identity of certain other rational, intelligent beings consists in
something else, or in nothing at all. (It may be, for instance, that we are biological
organisms that persist by virtue of some sort of brute physical continuity but there is
also an immaterial, personal god for whom this doesn t hold.) For this reason I will
speak of the identity of human people, not of people generally. Third, I will not
assume that a person must always persist as a person. I leave open the possibility
that each of us starts out as an unthinking embryo and may end up in a vegetative
state, and that we don t count as people at those times. So I will speak of the
identity or nonidentity of a human person existing at one time to a thing--person or
not--existing at another time.1 If these traditional assumptions turn out to be true,
my formulations will be equivalent to the usual ones and the difference will do no
harm.
A terminological note: although I have been speaking of the simple view , there
may be more than one view about personal identity that is not complex. In that
case we can take the simple view to name the proposition that some simple view
or other is true. Likewise for the complex view .
I take the simple view and its rivals to be views about personal identity over
1 For
further discussion of this point see Olson 1997a: 22-27.
2
time. There are other views about personal identity broadly speaking that have
certain affinities with this one. For instance Wiggins says that we cannot give a
complete account of what it is to be a person: personhood is, at least to some
extent, primitive and indefinable (1980: 171). Or someone might deny that there
are any nontrivial conditions for our transworld identity --that is, for how we could
have been. As these claims appear to be independent of the simple view of our
identity over time (they are answers to different questions), I will say nothing about
them.
There are also claims associated with the simple/complex debate that really are
about our identity over time, but not about whether it consists in something other
than itself. One is that our identity over time must always be determinate: there
could never be a being existing at another time that was neither definitely you nor
definitely not you. Another is that the facts of personal identity over time are
somehow up to us to decide rather than to discover. To my knowledge, all those
said to be advocates of the simple view deny both that our identity can be
indeterminate and that it can be up to us to decide--though some philosophers said
to hold complex views say the same.2 As I have been unable to discover any
important connection among these issues, I will set them aside.
3. Grounding and Criteria
Complex views are supposed to imply that if a person existing at one time is (or
is not) numerically identical with a being existing at another time, something must
make this the case--something beyond the mere fact that they are (or are not) the
same.
There seem to be two things that this might amount to. One has to do with how
our identity over time relates to other things: advocates of the complex view think it
consists in or depends on or holds by virtue of something other than itself. Not that
a future being s having inherited my mental states in a certain way (for example)
causes him to be me, in the way that stubbing my toe causes me pain. The
dependence is logical or metaphysical. So:
Whenever a human person existing at one time is identical (or nonidentical) to a
being existing at another time, this consists in something else.
Call this the grounding claim. Alternatively, personal identity might not consist in
anything else: it might be brute or primitive . An intermediate position is also
possible: that when a human person existing at one time is identical or
nonidentical to a being existing at another time, this sometimes consists in
2 Noonan
(2003: ch. 6) accepts that identity-statements can have an indeterminate
truth value, but denies that there can be indeterminacy of identity itself. Chisholm
(1976: 108-111), Olson (1997b), and Merricks (2001a) argue against identity
voluntarism .
3
something else and sometimes doesn t. There is no consensus about whether this
would count as simple or complex.
The second thought is that according to complex views there is a criterion of
identity for human people--not an evidential but a constitutive criterion, giving
conditions individually necessary and jointly sufficient for a human person to persist
from one time to another ( persistence conditions ). Consider this formula:
Necessarily, if x is a human person at time t and y exists at another time t*, x=y if
and only if...,
where = expresses numerical identity. The thought is that there a true completion
of the formula that is not trivial or otherwise degenerate. Call this criterialism.
Again, intermediate positions are possible. One is that there is a criterion of identity
for some kinds of people and none for others. Another is that there are certain
conditions necessary for a person to persist, and perhaps even certain sufficient
conditions, but no set of conditions individually necessary and jointly sufficient.3 In
fact every supposed advocate of the simple view that I know of accepts some
necessary conditions for personal identity: for instance that a thing existing at
another time can be me only if it is not then a stone. If there are any modal truths at
all, one of them is surely that it is impossible for something to be a human person at
one time and a piece of basalt at another time. (Or if one of us really could come to
be made entirely of stone, none of us could become abstract like the number
seven.) But this sort of thing does nothing to suggest any nontrivial sufficient
condition for our identity over time, or any way of completing the formula.
What is it for such a criterion to be nontrivial? Here are some that are trivial:
Necessarily, if x is a human person at t and y exists at t*, x=y iff x=y.
Necessarily, if x is a human person at t and y exists at t*, x=y iff an omniscient
being would believe that x=y.
Necessarily, if x is a human person at t and y exists at t*, x=y iff whatever is true
of x is true of y and whatever is true of y is true of x.
Necessarily, if x is a human person at t and y exists at t*, x=y iff x and y have the
same individual essence (where a thing s individual essence is a property that it
has essentially and that no other thing could possibly have).
The truth of these claims should not vindicate criterialism, and no friend of the
3 Merricks
2001b: 195f. Noonan (2003: 96f.) calls such views complex. If I am right
to say that everyone accepts some such necessary conditions, this implies that no
one holds a simple view.
4
simple view would deny them. They re not proper criteria of personal identity.
Why not? Well, they re entirely uncontroversial. And they are true not because
of the nature of personal identity, but because of the nature of omniscience or
individual essences or identity in general. Analogous principles apply to all
objects: the result of replacing the term human person with any other count noun
would be equally true and uncontentious. So the criteria tell us nothing about
personal identity as such. That seems to account for their triviality.
They are also uninformative, in that we could not know whether the conditions
were satisfied without already knowing whether identity holds. If Buggins suffers
severe and irreversible brain damage of a certain sort, we couldn t discover
whether the resulting being lying insensible on the hospital bed had Buggins
individual essence and use this to work out whether it was Buggins. Of course, an
informant might tell us whether it had Buggins individual essence; but the original
source of the information about essences could not have obtained it before
knowing who was who.
What s more, the examples fail to support the connection we expect to find
between a criterion of identity and an account of what grounds it. Obviously x
cannot be y because x is y. Nor can it be the case because an omniscient being
would believe it. The dependence is the other way round: whether an omniscient
being would believe something depends on whether it s the case. Likewise,
whether everything true of x is true of y depends on whether x is y, as one of the
things true of x is whether it is identical to y. Similar remarks go for the other
examples. These criteria cannot tell us what makes x and y identical or
nonidentical because they appeal to conditions that depend on whether this is so
(or , in the case of the first example, to the very fact to be accounted for).
There is more to be said about what makes a criterion of identity over time
substantive and nontrivial. Rather than exploring this further, I propose that a
proper criterion is one that completes this formula:
Necessarily, if x is a human person at t and y exists at t*, x=y iff and because...,
where the word because expresses the logical or metaphysical dependence of
the grounding claim. With any luck, this will avoid triviality and uninformativeness.
Criterialism, then, is the claim that some such criterion is true.
How the grounding claim and criterialism are related is a nice question.
Although criterialism as stated entails the grounding claim, the converse entailment
is less clear. You might think that if our identity consists in something else, it must
be possible to articulate that something else in the form of a proper criterion of
identity. But I don t know how to argue for this. Perhaps our identity over time could
consist in something that is not expressible in terms of necessary and sufficient
conditions. (Or perhaps there could be infinitely many such conditions, or even an
uncountable infinity. I leave open whether this would count as a criterion of
5
identity.)
4. Anticriterialism
Let us turn now to attempts to state the simple and complex views.
The most obvious proposal is that the complex view is criterialism and the
simple view is its negation, anticriterialism: that there is no proper criterion of
personal identity. Anticriterialism is probably the best candidate for being the
simple view. Yet it is such a strong claim that few if any supposed friends of the
simple view would accept it. Consider this thesis:
Necessarily, if x is a human person at t and y exists at t*, x=y iff and because the
thing that is x s soul at t is the thing that is y s soul at t*,
where a soul is an immaterial thinking substance, and a soul belongs to a particular
being at a time just if that being has its mental properties then by virtue of the soul s
having them. Call this Cartesianism. Some philosophers accept it, namely those
who think that we have souls as parts but are not ourselves souls--that a living
human person is composed of a soul and a body (Swinburne 1984: 21). In that
case, they say, a person existing now is identical to a being existing at another time
if and only if and because that being has the person s soul then. (If people are their
souls, by contrast, personal identity and soul identity are the same, and one cannot
depend on the other, contrary to Cartesianism.)
Cartesianism is far from trivial: it tells us something about human people in
particular, and is not true of concrete objects in general. It is also informative, in
that one needn t know whether x is y before knowing whether x has y s soul. There
may of course be practical obstacles to finding out whether we have the same soul
before finding out whether we have the same person, owing to the fact that we
cannot observe souls. But these obstacles appear to be only contingent.
So Cartesianism is a proper criterion of personal identity. It is a version of
criterialism, and thus, on the current proposal, a complex view. Yet it is considered
a paradigm case of a simple view (Swinburne himself calls it simple: 1984: 19).
Cartesianism also entails the grounding claim: it implies that personal identity
consists in something else, namely sameness of soul. (That is unsurprising, given
that criterialism entails the grounding claim.) This shows that both criterialism and
the grounding claim are too weak to capture what distinguishes complex from
simple views--assuming, at least, that the philosophical community is right about
where the boundary lies.
Accepting anticriterialism would mean rejecting all proper criteria of personal
identity. That would appear to rule out our being wholly material things, as in that
case there could hardly fail to be a criterion in terms of atoms or matter, even if not a
specific or satisfying one--something like the atomic criterion of 10.4 It would also
4 Zimmerman
1998. Merricks (1998) denies this, though I believe he would
6
rule out our being partly material and partly immaterial, as that would presumably
imply Cartesianism. It looks as if anticriterialists must say that we are wholly
immaterial souls.
They would also have to reject all nontrivial criteria for a soul existing at one
time to be identical to a soul existing at another time. For instance, there could be
no criterion in terms of causal relations, no matter how vague. Even the causaldependence criterion of 10 would be false. It would have to be metaphysically
possible that you are not the soul who read the previous sentence--that it ceased to
exist just now and you came into being in its place--even though all the causal
relations are exactly as they actually are (see Merricks 2001: 196). If we asked why
that soul perished, or why another appeared, there would be no answer. It would
not be because of the intervention of some deity, or a local disturbance in the
ectoplasmic field, or anything else. There would be possible situations that differed
only in the facts about our identity over time.
Well, someone could say that. But I don t know whether any real philosopher
ever has. It would be quite a surprise if this were the only possible simple view--if
some versions of substance dualism were simple and others, including those most
commonly held, were complex, and the difference turned on such arcane matters
as whether we are souls as opposed to soul-body compounds and whether any
sort of causal dependence is necessary and sufficient for a soul to persist. If that
were the simple view, it would hardly be worth including in the undergraduate
curriculum. Whether there are human souls is an important fact about our identity
over time, but whether there is any criterion of identity for them is at best a footnote.
5. Analyzability
Can we do better? The simple view is often said to assert that personal identity
is unanalyzable , and the question of what it consists in is sometimes put by asking
for an analysis of the concept of personal identity.5 This suggests that the issue at
stake is whether any proper criterion of personal identity could count as an
analysis. Analytic criterialism, then, would be the view that some such criterion is
analytic--that is, true by virtue of the concepts that figure in it, and the negation of
which can be transformed into an explicit contradiction by a process of analysis.
Analytic anticriterialism would be the view that no such criterion is analytic. Might
these be the complex and simple views?
Swinburne s main objection to complex views is in fact an objection to analytic
criterialism (1984: 18-20). It is a version of Moore s open-question argument .
Consider any criterion of the form: necessarily, if x is a human person at t and y
exists at t*, x=y iff and because x bears R at t to y as it is at t*, where R might be
some sort of psychological or brute physical continuity. Now imagine that some
accept the atomic criterion.
5 Noonan, for instance, says that according to the simple view personal identity is
an ultimate unanalysable fact, which resists definition in other terms (2003: 95).
7
future being really does bear R to you. Given this fact, Swinburne says, mere
logic --or logic together with the meanings of the relevant expressions--cannot
determine whether that being would be you. Neither those who say yes nor those
who say no would thereby contradict themselves or commit any other logical or
conceptual error. It is, as Moore would say, an open question. Thus, Swinburne
concludes, the proposed criterion cannot be an analytic truth. And this holds for
any proper criterion.
Whatever the merits of this argument may be, it does not rule out such a
criterion s being true, but at most its being analytic. So if this is an argument for the
simple view, the simple view must be analytic anticriterialism. And maybe
Cartesianism, if true, would not be analytic. That is certainly what the openquestion argument suggests: given that each of us is a compound of a soul and a
body, is it not an open question whether a being who has my soul at some other
time would have to be me? (Locke famously said no.) Suppose my soul had its
mental contents erased but was otherwise unharmed, and those contents were
then replicated in another soul. No amount of conceptual analysis can determine
whether I should then be the person with my original soul, the person with the new
soul and my replicated mental contents, or neither.6
But whereas ordinary anticriterialism was too strict to be the simple view,
analytic anticriterialism is too lenient: it is consistent with many views considered
paradigms of complexity. Consider this one:
Necessarily, if x is a human person at t and y exists at t*, x=y iff and because x s
biological life at t = y s biological life at t*,
where a biological life is a self-sustaining chemical event that always coincides
with a living organism (van Inwagen 1990: 83-90). If this were true, our identity
over time would consist in something other than itself, namely in the continuation of
a biological life--a sort of brute physical continuity (unless we are ourselves lives-but no philosopher I know of believes that). This is a complex view if anything is.
But it can hardly be analytic. Reflecting on the relevant concepts will never enable
us to work out that we persist just as long as our biological lives continue. If nothing
else, analytic truths are knowable a priori, and we cannot know a priori that human
people even have biological lives, never mind whether they must always go where
their lives go. So the life criterion is perfectly consistent with analytic anticriterialism
(and immune to Swinburne s open-question argument). Many other proposed
criteria that are considered complex are no more analytic: Unger s physically
based approach , for example (Unger 1990, ch. 5).
6 In
fact Swinburne takes Cartesianism to be analytic (personal communication). If
the simple view is analytic anticriterialism, that would make Cartesianism a
complex view.
8
6. Advocates of Analytic Criterialism
Would any view of personal identity count as complex if the simple view were
analytic anticriterialism? Does anyone think that what it takes for us to persist is
analytic? This would apparently mean that the concept of a human person had the
persistence conditions of human people built into it: that you could work out a
complete set of necessary and sufficient conditions for a human person to persist
just by analyzing the concept of a human person. You might suppose that it is not
the concept of a person, but the concept of personal identity over time that has the
criterion of personal identity built into it. But what is the concept of personal identity,
if not the concept of identity applied to people? And the concept of identity (or of
identity over time) by itself provides no substantive criterion of identity. So if the
criterion of personal identity is analytic, it must derive from the concept of a person.
I know of two views that may have this consequence.7 One is Shoemaker s
theory that mental properties, by their very nature, give their bearers causal powers
that fix their persistence conditions (Shoemaker 1999). It is a familiar thought that
mental states are by nature disposed to combine in certain ways with other mental
states to produce certain effects: this is the core of the functionalist theory of mind.
Shoemaker adds to this the further claim that a mental state must be disposed to
combine in this way only with states of the same subject, and to produce the
relevant effects in that subject alone. Your being hungry, for instance, must tend to
cause you to eat if you believe there is food before you, unless you have some
competing goal--you and only you. Thus, any being that was caused, in this way, to
eat by your state of hunger must be you. It follows that some sort of psychological
continuity suffices for you or any other psychological being to persist.8 If a person
is by definition a sort of psychological being, and if Shoemaker s theory of mental
properties is analytic , then this account of personal identity will be analytic, and
presumably a version of analytic criterialism.
A view that pretty clearly makes the conditions of personal identity analytic is the
ontology of temporal parts or four-dimensionalism . It implies that for every
candidate for being the career or history of a human person, and every part of such
a candidate, there is a conscious, intelligent being whose history it is. So there is
now a being sitting here that is just like me, both physically and mentally, except
that it came into being at midnight last night and will cease to exist at midnight
tonight. Another such being came into existence when my biological life began,
some sixteen days after I was conceived, and will cease to exist when my life ends.
Yet another came into being at conception, and will persist after my death as a
corpse until my remains become dust. Many more such beings share my current
7 Another
possible candidate is Parfitian reductionism , but I don t understand it
well enough to know for sure. Shoemaker 1985 and Noonan 2003: 97-100 are
good discussions. Merricks (1998: 111-116) argues against analytic criterialism.
8 Though whether psychological continuity would be necessary for a person to
persist is less clear; see Olson 2002.
9
stage. But according to most four-dimensionalists, only one of these beings
(vagueness aside) is a person. Being rational and self-conscious is therefore
insufficient for personhood. In fact the vast majority of beings psychologically like
ourselves are not people, but merely share temporal parts with a person.
To say what it is to be a person, on this view, we have to say what it takes for a
person to persist. Thus Lewis (1976), for example, says that a person is a maximal
aggregate of psychologically interconnected person-stages. A person-stage is a
more-or-less momentary being with the mental properties that characterize people:
rationality and self-consciousness, perhaps. Two person-stages are
psychologically connected when one inherits its psychological properties from the
other in a special direct way: when one has a memory of an experience of the
other s, for instance. An aggregate of psychologically interconnected personstages is a being composed of person-stages, each of which is psychologically
connected with every other, and it is maximal when it is not a part of any other such
aggregate. This gives the conditions necessary and sufficient for a person to
persist. And because it is part of the definition of person , it is analytic if anything is.
But this can hardly be the frontier between simple and complex, with views like
Lewis s and Shoemaker s on the complex side and all the rest, including those of
Unger and van Inwagen, counting as simple.
7. Empiricist Theories
Another issue sometimes discussed in connection with the simple/complex
debate is whether personal identity consists in any of the conditions we use as
evidence for judgments about it. Swinburne complains that some philosophers fail
to distinguish between evidential and constitutive criteria: their account of the
logically necessary and sufficient conditions of personal identity [is] in terms of the
evidence of observation and experience which would establish or oppose claims of
personal identity (1984: 3; for similar remarks see Chisholm 1976: 111-113). He
calls these empiricist theories of personal identity.
Might complex views be empiricist theories? Is this the issue at stake in the
simple/complex debate--whether there are conditions individually necessary and
jointly sufficient for personal identity that we use as evidence for claims about who
is who? Well, what do we use as evidence for these claims? What is the basis for
my belief that the man emerging from the office next door is my colleague Nils,
rather than another colleague or a complete stranger? Well, he looks like Nils did
when I last saw him. And he acts like Nils: he greets me rather than staring
blankly, and responds as Nils has in the past when engaged in discussion about
departmental matters. And I take it to be rare for someone to look and act so much
like someone else as to fool his colleagues. Our primary evidence for claims about
personal identity seems to be physical and behavioural similarity.
If an empiricist theory is one according to which there is a criterion of personal
identity in terms of our primary evidence for such claims, then empiricists are those
10
who hold that our identity over time consists in physical and behavioural similarity.
But no one thinks that. Even if we could specify the respect of similarity generously
enough to allow for the fact that people s appearance and behaviour change
radically between infancy and old age, no one thinks that mere similarity of any sort
is sufficient for identity: there could be someone other than Nils whose appearance
and behaviour were as similar to his as you like.
This cannot be what Swinburne meant by an empiricist theory. What did he
mean? Well, we take physical similarity to be evidence for some sort of physical
continuity--causal dependence of later physical states on earlier ones--and we take
behavioural similarity to be evidence for psychological continuity, which is also a
sort of causal dependence. And many philosophers think that physical or
psychological continuity is not merely evidence of personal identity, but what it
consists in. So perhaps empiricist views are those according to which there is
some condition that we use as evidence--not necessarily as primary evidence--for
judgments about personal identity, which figures in a proper criterion of personal
identity.
But this would make Cartesianism an empiricist theory. If it were true (and we
knew it), physical and behavioural similarity would be evidence for sameness of
soul: I should be warranted in believing that the man next door has Nils soul
because he looks and acts like Nils. At any rate this is consistent with
Cartesianism. (It would be bad news for Cartesians if it were not true: it would
seem to deprive us of any evidence for claims about who is who.) Yet having the
same soul would not only be evidence of personal identity, but what it consists in.
You might suppose that Cartesianism is not an empiricist theory because the
condition that it takes personal identity to consist in is not observable: which
human being has which soul is not evidence of observation and experience . But
psychological continuity is not observable either. Both have to be inferred (in
others, if not in oneself) from behavioural similarity.
So it looks as if Cartesianism is an empiricist theory if psychological-continuity
views are. This is not the right boundary either.
8. Bruteness
What could make Cartesianism, but not physical- or psychological-continuity
accounts, a simple view? Perhaps this: even if personal identity consists in identity
of soul, identity of soul consists in nothing. Nor is there any criterion of identity for
souls. Though personal identity may depend metaphysically on something else,
that something else does not itself depend on anything further. So this might be the
simple view: personal identity either consists in nothing (that was anticriterialism,
or near enough), or consists in the identity of something else which consists in
nothing. Alternatively, if there is any proper criterion of identity over time for human
people, it appeals to the identity of something for which there is no such criterion.
(For present purposes we can ignore the difference between these two variants.)
11
Call this proposal bruteness.
But some Cartesians deny bruteness. Swinburne, for instance, used to say that
souls, like all substances, persist by virtue of sameness of form and continuity of
stuff, so that their identity is not brute (1984: 27; 1997: 153f.).9 To make
Cartesianism compatible with bruteness, you would have to combine it with
bruteness about souls (a view briefly explored in 4). It would be pretty surprising if
this were the frontier between simple and complex views. There are also views
everyone would classify as complex that are consistent with bruteness. Someone
who endorsed the life criterion of 5, but believed that identity of lives was brute,
would accept bruteness. Or imagine a Humean who believed that people are, as
the great man said, nothing but bundles of impressions , and who endorsed the
following criterion: if x is a human person at t and y exists at t*, x=y iff and because
y is composed of impressions at t* and a certain proportion of those impressions
are also parts of x at t. Combined with the view that there is no criterion of identity
for individual impressions, this would entail bruteness.
9. Noonan s Proposal
Harold Noonan (2011) has recently proposed a subtle refinement of bruteness.
The simple view, he says, is that the only necessary conditions on personal identity
belong to a certain special sort. A condition will belong to this sort if it follows from
what it is to be a person (or a human person) at a moment. For instance, you can t
be a person at a moment if you re made entirely of stone then. Supposing, as
Noonan does, that whatever is a person at some time must be a person whenever it
exists (which we can grant for the sake of argument), it follows that no past or future
being can be you if it is made entirely of stone at that time. But as everyone accepts
this, it ought to be consistent with the simple view. Noonan calls such conditions
synchronic . Conditions that are trivial in something like the sense discussed in 3
are also compatible with the simple view. And so are conditions that are identityinvolving : those that require the identity over time of something other than the
person in question. For instance, Cartesianism implies that a past or future being
can be you only if it then has the same soul as you have now, where a soul is not a
person. This is compatible with the simple view. The simple view, then, is that the
only necessary conditions for personal identity are either synchronic, trivial, or
identity-involving. Complex views assert further conditions.
Like the previous proposal, Noonan s implies that at least some versions of
Cartesianism are complex, depending on what conditions they impose on the
identity of souls. If the only conditions for soul identity are synchronic (if they follow
from what is necessary for a thing to be a soul at an instant), trivial, or identityinvolving, then Cartesianism may be a simple view. But if there are other
9 He
has since revealed in personal communication that he no longer holds this.
But he does not say that he once held a complex view and now holds a simple
view.
12
necessary conditions for a soul to persist--for instance, if it requires a soul s later
states to depend causally in some way on its earlier ones--then these will also be
conditions for personal identity, and the Cartesian view will count as complex.
Likewise, it appears to count some versions of the life criterion and the Humean
view as simple.
If I have understood it, Noonan s proposal makes the simple view so strong that
no one actually holds it. No philosopher I know of would accept that a person could
be wholly material at one time and wholly immaterial at another. If you are now
made up entirely of matter, then no being that is not made up even partly of matter
at some other time can be you. Likewise, if you are wholly immaterial now--if you
are a Cartesian soul, say--then you could not come to be made up entirely of
matter. This is not a synchronic condition for personal identity: it doesn t follow
from what it is to be a person, or even a human person, at a moment. From the
mere proposition that x is a human person at t, it doesn t follow either that x is
material at t or that x is immaterial at t, never mind that x is material or immaterial at
any other time. So it seems, anyway. Nor is the condition trivial or identityinvolving. If so, Noonan s proposal implies that you hold a simple view only if you
reject this condition: only if you think it is possible for one of us to change from
being wholly material to being wholly immaterial or vice versa. But every supposed
advocate of the simple view accepts the condition.
10. Specific and Unspecific
I can offer no better account of what makes a view simple or complex. As far as I
can see, no principle divides views about personal identity in the right place, or has
the importance that the simple/complex distinction is traditionally ascribed. Let me
finish by trying to say something positive. Suppose the traditional taxonomy of
simple and complex views really is hopelessly wrongheaded. What ought to
replace it? How should views of personal identity be categorized? What are we to
tell our students?
Well, we can still divide views into those that appeal only to brute physical
conditions, those that appeal to some sort of psychological continuity, and those
that appeal to neither. This is an important three-way distinction.
Someone might suggest that simple views are precisely those appealing neither
to brute physical nor to psychological conditions--thus making the simple/complex
distinction irreducibly disjunctive. That would make most versions of Cartesianism
simple--the exception being those that give psychological persistence conditions
for souls (Foster 1991: 240-261). But this would be to abandon all our original
starting points. It would do away with the thought that complex views take our
identity over time to consist in something while simple views deny this. There are
views according to which personal identity over time consists in something other
than brute-physical or psychological continuity--or, for that matter, identity of soul.
Kantians, for instance, might say that it consists in something noumenal that we can
13
form no conception of. The disjunctive proposal would count these as simple
views. But shouldn t they count as complex? It would also give up the conviction
that simple views differ from complex ones over something more fundamental than
what personal identity consists in, instead putting their difference on a par with that
between physical and psychological views.
Here is something else we can tell our students. Criteria of personal identity
differ enormously in how much information they provide. This one tells us rather
little:
Necessarily, if x is a human person at t and y exists at t*, x=y iff and because the
total state of x at t depends causally in an appropriate way on the total state of y
at t* or vice versa.
It says only that personal identity consists in some sort of causal dependence.
That s not trivial. If it s true, it is because of the metaphysical nature of human
people. It may not hold for all objects, or even all concrete objects. It is not true of
shadows and sunbeams, if there are such things: their earlier states don t cause
their later ones. It has controversial implications: it rules out our surviving without
any sort of causal dependence on our earlier states, contrary to some views about
life after death (e.g. Baker 2005, Hick 1990: 123f.). But beyond that it s useless. It
says nothing about what sort of causal dependence our identity consists in. Think
of cases where it s hard to know who is who, even if we know everything else.
Suppose we ask whether reincarnation is possible, or what would happen to
someone whose brain was transplanted into a different head. The causaldependence criterion is consistent with any answer to these questions.
Or consider this atomic criterion (adapted from Zimmerman 1998):
Necessarily, if x is a human person at t and y exists at t*, x=y iff and because the
arrangement of x s atoms at t and the arrangement of y s atoms at t* both belong
to an atomic history of the sort that necessarily any human person has, and
which is necessarily the history of a human person,
where the arrangement of x s atoms includes both the intrinsic nature of the atoms
composing x and their spatiotemporal and causal relations to one another and to
other atoms, and someone s atomic history is a complete description of her atoms
throughout her existence. This is not trivial either. If it s true, it is because of how it
is with human people and not merely because of the nature of atomic histories and
arrangements. It has controversial implications, ruling out our surviving without
being composed of any atoms at all. But it tells us no more about what happens in
most of the puzzle cases than the causal-dependence criterion does.10
10 It
may be that these are somehow not proper criteria of identity, and thus ought
to be consistent with anticriterialism, supporting the claim that anticriterialism is the
14
These accounts are enormously unspecific about what it takes for us to persist.
The life account, that a past or future being is you just if it then has your current
biological life, is far more specific. It tells us who would be who in most of the
puzzle cases. The same goes for familiar psychological-continuity views.
Yet even these views are less specific than they might be. The precise sort of
causal dependence that psychological continuity consists in is elusive. No matter
how much detail an account provides, there will be possible cases where a being
existing at another time has mental states that depend causally on yours now (or
vice versa) in such a devious way as to leave it unclear whether he or she is
psychologically continuous with you. And even if we could specify the sort of
causal dependence, psychological continuity will be a matter of degree, and it is
hard, if not impossible, to say precisely what degree is needed. I have never seen
a psychological-continuity account specific enough to tell us, in conjunction with the
relevant underlying facts, in every case whether the resulting being would be you,
or not you, or whether it would be indeterminate whether it was you.
You might think this is only because no has taken the trouble to write out a
completely specific psychological-continuity view, or because no one knows
enough to do it. More generally, it may be that if some less specific account of
personal identity is true, it must be because it follows from some more specific
account--perhaps even a maximally specific account that would entail, in
conjunction with the underlying conditions, all the facts about personal identity over
time. I have no idea whether this is the case. There is certainly reason for doubt.
Shoemaker, who has thought about these matters as deeply as anyone, confesses
that it seems impossible to specify the sort of appropriateness that figures in the
causal-dependence criterion without already knowing the precise conditions under
which human people persist (1979: 337). You might think it is impossible only for
finite minds: God must be able to do it. But who knows? It s worth noting that
Merricks, who presumably accepts the atomic criterion, explicitly denies that there
is any more specific criterion of personal identity (1998).
So here is an important difference among criteria of personal identity: some
give us quite specific information about what our identity over time consists in, while
others say little. This bears some affinity to the traditional simple/complex
distinction: those views called complex often appear more specific than those
called simple.
But the simple/complex distinction is not that between unspecific and specific
views. For one thing, the difference between more and less specific is a matter of
degree, while the simple/complex distinction is supposed to be absolute: we tell
our students that some views of personal identity are simple and others aren t, not
that some are more simple than others.
And the two distinctions divide the territory in different ways. The causalsimple view. Those with this suspicion will want to think about what makes them
improper.
15
dependence criterion is normally taken to be a complex view: Shoemaker explicitly
contrasts it with that of Butler, Reid, and Chisholm that the cross-temporal identity
of genuine continuants [cannot] be said to consist in the holding of any relations
other than the relation of identity itself (1979: 323). Yet it is consistent with the
absence of any more specific criterion. Nor is it clear whether the soul criterion is
any less specific, even though it is supposed to be a simple view. Think of
reincarnation again. Could someone born after my death be me? The causaldependence criterion gives an ambivalent answer: only if that being s state then
depended causally in the appropriate way on mine before my death. But it says
nothing about what way is appropriate, or whether it could be appropriate in this
case. The atomic criterion tells us even less. The soul criterion gives what sounds
like a more specific answer: such a being would be me if and only if it had my
immaterial soul. If you were a deity wanting to reincarnate human people, this (if
true) would be far more useful information. Thus, some views traditionally taken to
be complex appear, if anything, to be less specific than views considered simple.
And the distinction between less and more specific may be not only a matter of
degree, but context-relative. The soul criterion might be less specific than the
causal-dependence criterion relative to some contexts and more specific relative to
others--as in the case of our imaginary deity. But I doubt whether anyone ever took
the simple/complex distinction to be context-relative.
11. Explanatory Demands
The distinction between specific and unspecific criteria of identity is closely
related to a difference in expectations. Philosophers discussing personal identity
often make explanatory demands. Suppose once again that we are considering
the possibility of reincarnation. Here is an almost irresistible question: What could
make it the case that some infant born after I am dead was me? Out of all those
future newborns--many billions of them--what could make this one me, rather than
some other one? To put it the other way round, what could make it the case that a
certain infant born after my death was me rather than someone else--you, say, or
Socrates, or someone who had never existed before? Or if reincarnation is
impossible, we shall want to know what makes it impossible. What is it about the
way someone born after my death would have to relate to me that would
necessarily rule out its being me?
Philosophers disagree about when such explanatory demands are legitimate:
about what must have an explanation in matters of personal identity, and where
explanation comes to an end and we face brute facts. They disagree about which
questions must have answers. They also disagree about what sort of answers we
can expect. At one extreme, someone might say that an infant born after my death
could be me but nothing would have to make it me. It would not have to be me
because it had my soul, or because its bore any psychological relation to me, or
because its states then depended causally in a certain way on mine now, or
16
because God willed that it be so. It could simply be me, and that would be that.11
At the other extreme, someone might say that such an infant could not possibly be
me because its total state then would not bear to my total state now the sort of
causal dependence that is both necessary and sufficient for personal identity; and
she might be able to describe this relation precisely. (Certain versions of the life
criterion might be like this.) Nearly all the answers actually proposed--both those
considered simple and those considered complex--fall between these extremes.
When it comes to personal identity, some philosophers expect more facts to be
explained than others do, and there is probably some correlation between this and
whether one holds a view classified as complex or one classified as simple. But
the correlation is far from perfect. Nor can I see any way of transforming this
difference of expectations into a difference of doctrine.
The simple view remains elusive.12
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