(intro music)
Okay, this is part two
of our discussion of personal identity over time,
and I'm still Michael Della Rocca,
identical to the person who gave
the part one of this lecture.
So let's continue now.
We started by discussing the general problem
of personal identity over time
and how it's related to some more
general metaphysical problems.
Now I want to begin to look at particular solutions,
or attempted solutions, to this problem
of personal identity over time.
Traditionally, two answers to this problem
have been very popular.
One might think that the sameness
of persons over time consists in
what might be called "the sameness of soul over time."
On this view, and perhaps this view
is attributable to the philosopher Descartes,
the soul is a non-physical thinking thing,
or thinking substance,
and the soul is distinct from the body,
though it is, perhaps, associated with the body
in important ways.
On this quasi-Cartesian view of personal identity,
for an earlier person A to be identical
to a later person B, it is both necessary
and sufficient for the earlier person A
and for the later person B to have the same soul.
On this view, sameness of body
is not relevant to personal identity.
The only thing that's relevant to personal identity
on this view, this Cartesian view,
is the sameness of soul,
the sameness of thinking substance.
On an alternative answer to this problem,
an answer often associated with materialists,
sameness of person consists in sameness of body,
sameness of the human body.
For A to be identical to B,
it is both necessary and sufficient
that A and B have the same body.
On this view, sameness of soul,
if indeed we have a soul,
is irrelevant to personal identity.
Now these are deep and competing accounts
of personal identity.
On the first view, we are fundamentally souls,
or thinking substances.
On the second view, we are fundamentally our bodies,
our human body.
Now, it's a deep insight of Locke
to envisage a completely different
kind of account of personal identity.
His account cuts across each of the two
previous accounts in important ways.
On Locke's account, sameness of person
consists not in sameness of soul
nor in sameness of body,
but in sameness of what he calls "consciousness."
This is the philosophical progress
that Locke has given us:
to give a completely new account of personal identity
in terms of sameness of consciousness.
But what exactly does he mean
by "sameness of consciousness?"
This is a complicated matter,
and to answer this question,
I want to turn to a completely different
kind of case, involving not persons, but plants.
This will provide a helpful analogy
with Locke's account of persons,
if we consider Locke's account
of what might be called "plant identity over time."
We may never have thought about
plant identity over time,
but it is important, because it can help us
to see the nature of Locke's account
of personal identity over time.
So let's turn to Locke's account of plant identity,
or of organic creatures in general.
To answer the question of plant identity over time,
let's draw a distinction between the plant itself
and the molecules or atoms that make up the plant
at any one time.
Following Locke himself, let's call the collection
of atoms that makes up a plant a "mass of matter."
Such a collection of atoms is, for Locke,
a physical or corporeal substance.
Now, the mass of matter that makes up
a particular plant - let's say a rhododendron -
let's call her "Rhoda" - okay, Rhoda the rhododendron -
now, the mass of matter that makes up
a particular plant at a certain time,
a time T1 let's say,
that mass of matter is different from
the mass of matter that makes up Rhoda,
that same rhododendron, at T2.
That's the beautiful thing about organic creatures:
they gain and lose matter all the time.
That's just the kind of thing that they do.
Now, it's natural to think that Rhoda, the plant itself,
persists through this change in masses of matter.
It's gaining and exchanging matter
with the environment all the time.
So there's a change in physical substance.
So the mass of matter that constitutes Rhoda at T1
is different from, completely non-identical to,
the mass of matter that constitutes Rhoda at T2.
And it may well be the case that through
some kind of great coincidence,
Rhoda loses all of the bits of matter
that make Rhoda up at time T1.
And so the mass of matter, let's call this mass of matter "one,"
that constitutes Rhoda at T1,
does not constitute Rhoda at time T2.
In fact, and this is the coincidence,
it could turn out that the mass of matter
that constituted Rhoda at time T1
comes to constitute a completely different plant,
let's call it "Phyllis," at T2.
And at time T2, there's a mass of matter "two,"
that constitutes Rhoda.
So Rhoda's now constituted by mass of matter two,
and at time T2, a different plant, Phyllis,
is constituted by mass of matter one,
the mass of matter that originally constituted Rhoda.
We can see from this that we have different
masses of matter constituting the same plant
at different times, and we have the same mass of matter
constituting different plants at different times.
Thus, the sameness of mass of matter is neither
necessary nor sufficient for sameness of plant.
What, then, is necessary and sufficient
for the sameness of plant?
Locke's answer is clear:
for a plant at T1 to be identical to a plant at T2,
the earlier plant and the later plant
must have the same, or roughly the same, organization,
the same way in which matter is structured,
and there must be a certain continuity
between the organization of the plant at T1,
at the earlier time, and the organization
of the plant at T2.
As Locke indicates, the earlier plant
and the later plant must partake of the same life,
which is communicated in a continuous fashion
to different particles of matter at different times.
For a plant to exist at a time
is for matter to have a certain organization at that time.
And for a plant to persist from one time
to another is for there to be a continuously
maintained organization of matter,
despite the fact that this organization
is realized in different molecules,
or different bits of matter, at different times.
I have touched on this topic of plants
not just because I love to talk about plants,
but also because the account of the persistence
of plants is analogous to Locke's revolutionary
account of the persistence of persons.
So let's return to persons.
For Locke, just as what it is for a plant to exist at a time
is for matter to be organized in a certain way,
for a person to exist at a certain time
is for there to be a thinking, intelligent being,
that is, reason and reflection.
And more generally, for there to be a person
at a give time is for there to be something
that has consciousness at a given time.
Plant identity requires that there be a substance
with a certain organization of matter.
Personal identity requires that there be
some kind of substance with a certain consciousness
and the ability to reflect on itself.
And just as it is necessary for plant identity over time
that this organization be maintained,
even if the physical substances that exhibit
this organization change,
so, too, it is necessary and sufficient
for personal identity over time
that this consciousness be maintained
even if the substance that exhibits
this consciousness changes.
So personal identity consists in continuity
of consciousness, just as plant identity
consists in continuity of organization of matter.
For Locke, the substance that exhibits
the consciousness at a time is probably a soul
or a purely mental, immaterial substance.
But Locke does think that it's conceivable
that the substance that exhibits consciousness
be material, or a body.
He's agnostic on that point, actually.
But the key point for the account of personal identity
is that for Locke, the sameness of soul
is neither necessary nor sufficient
for the sameness of person.
Similarly for Locke, the sameness of body
is neither necessary nor sufficient
for the sameness of person.
Instead, for Locke, sameness of consciousness
is both necessary and sufficient
for the sameness of person.
This is Locke's radically new answer
to the question of personal identity.
Persons are not fundamentally souls
and they're not fundamentally bodies.
Rather, persons are, in a way,
fundamentally their consciousnesses.
To illustrate this point, we need to see
what Locke means by sameness of consciousness.
Roughly, Locke's account of sameness
of consciousness is this:
a later person, B, exhibits the same consciousness
as an earlier person, A, if and only if
the later person can remember
the earlier person's thoughts and actions.
More slowly, there are two claims here that are relevant.
The first claim is this (this is the claim of sufficiency):
if B, the later person, can remember A's thoughts
and actions, then A is the same person as B.
That's the claim of sufficiency.
Now here's the claim of necessity:
if A is identical to B, then B can remember
A's thoughts and actions.
In other words, if B doesn't remember A's
thoughts and actions, then A is not identical to B.
So on this view, sameness of consciousness
consists in the ability to have memory connections
between the later person, B, and the earlier person, A.
Locke exhibits this kind of view with a number of examples.
Let me give one of my own.
If the consciousness of Barack Obama
should start informing my body or my soul,
such that in my body or soul there are somehow
now the memories of all the things that Obama has done,
if this body starts talking like Barack Obama,
starts getting an incredible urge to veto legislation,
then that would be a case in which
the conscious of Barack Obama
has come to inform this body or this soul,
my body or my soul.
If that's the case, that would mean,
according to Locke, that the person Obama
now inhabits my body.
At the same time, let's say that, fortunately
or unfortunately for Obama's body,
my consciousness begins to inform
Barack Obama's body or soul,
such that in Obama's body or soul, somehow,
are the memories of my life,
of all the things that I have done.
My consciousness, or memories, have migrated,
it seems, from my body to Obama's body or soul.
So that's a case in which Obama is,
in some sense - the person Obama
is in some sense now in my body,
and the person, Michael Della Rocca,
that person, MDR, is now in Obama's body.
We've switched bodies in a way.
On Locke's account, personal identity
goes where the consciousness or memory goes,
regardless of what soul or body is in question.
That's what makes possible this person
switching bodies, or person switching souls.
Persons go where their consciousness goes.
In the same way, as you saw with the plants,
the plants Rhoda and Phyllis can, as it were,
switch bodies or masses of matter.
There can be body switching there.
Similarly, just as plant identity goes
with sameness of organization
and not sameness of material substance,
so, too, personal identity goes with
sameness of consciousness
and not sameness of substance.
This account, whereby sameness of consciousness
or memory is both necessary and sufficient
for sameness of persons, is actually quite plausible.
I'm sure you've seen movies where there have been
body switching, where persons have switched bodies.
Freaky Friday was an example of such a movie.
There's a kind of plausibility there.
If some body begins exhibiting my memories
and my thoughts and my intentions, et cetera,
that's where I am.
I go where my consciousness goes.
That's Locke's account of personal identity
in terms of consciousness.
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