What is "personal
identity"? We know from intuitive self-awareness that personal
identity exists. It's a fact of conscious life, as common as the word,
"I." But how to define it?
the ancient world provide little guidance, and modern philosophers have only
framed definitions in the form of a problem. Harold Noonan, in
his survey of the subject, states this problem in terms of "logically
necessary and sufficient conditions":
The problem of personal identity over
time is the problem of giving an account of the logically necessary and
sufficient conditions for a person identified at one time being the same
person as a person identified at another.
That's one definition. Noonan's use
of the adverb "logically" may exaggerate the logician's limited role.
The Oxford Companion to Philosophy
states the problem a bit more generally:
The problem is to say in an informative way
what the necessary and sufficient conditions are....
Everyone maintains personal identity;
it persists irrespective of our individual traits. Personal identity is the "common denominator" of soul: where
personal identity persists, a soul will surely be found. So if we are to improve our
knowledge of the soul's overall function and nature, it's very likely we'll need to tackle the problem of personal identity first.
The implication of "problem definitions" is that our best definition of personal identity
would be one which captures its necessary and sufficient conditions, and in a manner
which is most "informative." This suggests a
plan for the chapter. We'll focus on each of the conditions which modern
philosophers consider necessary for the maintenance of personal identity. Once we've narrowed each condition down to some
more distinct criterion, we'll follow the example of Chapter 6 and hunt for that
criterion's corresponding corporeal function. Wherever a corporeal
function can be found, that function strengthens the argument for complete mortality
developed in Chapter 7. And more than that — it also unearths the second metaphysical key, which shall remain nameless for now.
We might expect
this study of personal identity to be a lengthy task. But as it turns out, only three
"Great Criteria" of personal identity are actually known; so we're
working down a short list. Moreover the critique of Proclus' Elements, finished in Chapter 7,
has given us a time-saving shortcut; as we'll see below.
First Criterion: Memory
In the previous chapter we considered the
memory to the conscious mind. It
is "the cabinet of imagination, the treasury of reason, the registry of
conscience, and the council chamber of thought," to use St. Basil's
to the thinking mind has never been controversial. What has at times been controversial is the value of memory with respect to
personal identity. John Locke started this argument all by himself, back in
1694. Here's his groundbreaking assertion, from An
Essay Concerning Human Understanding:
For since consciousness always
accompanies thinking, and 'tis that, that makes every one to be, what he
; 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
John Perry clarifies the final sentence of
Locke must mean something like this:
"Any experience I can remember being reflectively aware of, is mine,
i.e., one that happened to me." Thus the distinction between
knowing of present experiences by our five external senses and knowing of
them by our sixth inner sense is carried over into memory; all and only
experiences I can remember having been aware of in this latter way were
Taken literally, Locke's statement demands
too much. It requires that our minds remember everything that has ever
happened to us, forgetting nothing along the way. Of course, we cannot
. Acknowledging this fact,
and H. Paul
have modified Locke's
theory to accommodate forgetfulness. More recently, Perry
has worked to remove circularity from
Grice's version of the theory. Otherwise this line of reasoning hasn't
changed much since Locke's day.
Shoemaker, a prominent critic of this "memory theory":
It is, I should like to say, part of the
concept of a person that persons are capable of making memory statements
about their own pasts. Since it is a conceptual truth that memory
statements are generally true, it is a conceptual truth that persons are
capable of knowing their own pasts in a special way, a way that does not
involve the use of criteria of personal identity, and it is a conceptual
truth (or a logical fact) that the memory claims that a person makes can be
used by others as grounds for statements about the past history of that
person. This, I think, is the kernel of truth that is embodied in the
view that personal identity can be defined in terms of memory.
Locke's memory theory has withstood three
hundred years of criticism pretty well. Memory would seem to be a
necessary condition of personal identity.
Having found a necessary condition, we
should like to narrow that condition down to some more distinct corporeal criterion, if
possible. But philosophers have not always been clear in stating just
of memory is necessary for personal
identity, and this makes the task a bit more involved. There are, actually,
several known types.
If we work down the hierarchy of
these memory types, we can find the one most clearly essential to personal
identity. This will be our criterial candidate for "Lockean
memory" — that type of memory essential to personal identity.
So, starting at
the top of the hierarchy:
At the highest
level, memories divide into short-term and long-term types. The memory
required by personal identity must be retained over the span of a
lifetime. Hence Lockean memory is long-term.
memories can be either implicit or explicit. Implicit memories are skills
and habits: memories with no "truth value." Explicit memories
have truth value, and can be proved true or false. When we recall an
experience from life, our recall may be accurate or not. By comparing our
recall with factual history we can determine the memory's truthfulness. So Lockean memory is not just long-term, but
explicit memories are of two types: facts and events. Memories of facts
are unrelated to one another. For example: I may recall a
photographic image of a deer, and also an unrelated photo of a tree with a patch
of stripped bark. The two factual memories are disconnected, separate.
Memories of events "associate" such isolated data.
Continuing the example: While walking through the forest, I see a buck
deer rubbing his antlers against a tree in order to remove the antlers' itchy velvet. In
future I will associate the two prior images, those of a deer and a stripped tree, together in
this novel event. Presentation of either image will bring the associated
event to mind.
autobiographical memory — a memory of a unique, personal experience —
associates sensations together in the record of that
experience. That record constitutes a remembered event. Therefore Lockean memory is not just
long-term explicit, but specifically it is the memory of
long-term explicit events.
A taxonomy of
memory types is highlighted so as to trace this deduction:
A taxonomy of
The colored junctures trace the
deduction of long-term explicit event memory.
have narrowed Lockean memory down to one specific type: that of long-term explicit events.
(Truth be told, it's a deduction now common, even popular.)
And this is where our critique of
Proclus' Elements provides
We saw in
Chapter 6 that memories of events (episodic memories) are stored in the neocortex, and retrieved
from the neocortex, through the autoassociative function of the
hippocampus. Autoassociation binds recursion to the living,
Now we can make
use of this knowledge again. We simply note that the function which binds
recursion to the body also binds Lockean memory to the body.
care of the memory criterion.
Conclusion: The memory criterion of personal identity has a
next Section 2 of 4
Chapter 8, Section 1 Endnotes
Harold W. Noonan, Personal Identity
(London: Routledge, 1989) 2.
Paul F. Snowdon, "Personal Identity," Oxford Companion to Philosophy
(Oxford: Oxford University Press, 1995)
654-55. Related texts online.
An Essay Concerning Human
, ed. Peter H. Nidditch (Oxford: Clarendon Press, 1979) 335,
Chapter 27, Section 9. This quotation is taken from the chapter entitled "Of Identity and Diversity."
That chapter was an addition to the second edition of the essay, published in 1694.
John Perry, "The Problem of Personal Identity," Personal Identity
, ed. John Perry (Berkeley: University
of California Press, 1975) 14-15. Related texts online.
Anthony Quinton, "The Soul," Personal Identity
H. Paul Grice, "Personal Identity," Personal Identity
John Perry, "Personal Identity, Memory, and the Problem of
Circularity," Personal Identity
Sydney Shoemaker, "Personal Identity and Memory," Personal Identity
A good historical review of the study of mammalian memory can be
found in Milner, Squire, and Kandel 445-68.
Milner, Squire, and Kandel 451.
See, for example, Rocco Gennaro's recent (1996)
version of the "episodic memory argument" in Rocco Gennaro, Consciousness and self-consciousness
(Amsterdam: John Benjamins Publishing Company, 1996)
182-200. Gennaro builds an interdisciplinary argument wherein
he equates consciousness quite explicitly with the ability to fashion episodic memories (long-term
explicit event memories).