mbd_map 19: A Dedication homepage homepage forum lectures 1: A Word of Encouragement 2: Dar al-Hikma 3: Proclus' Elements 4: Reversion in the Corporeal 5: Mathematical Recursion 6: Episodic Memory 7: Mortality 7 Supplement: Classical Mortality Arguments 8: Personal Identity 9: Existential Passage 10: Precedent at Dar al-Hikma 10 Supplement: Images of Dar al-Hikma 11: Passage Types 12: A Metaphysical Grammar 13: Merger Probability 14: Ex Nihilo Probability 15: Noetic Reduction 16: Summary of Mathematical Results 17: Application to Other Species 18: Potential Benefits 19: A Dedication appendices works cited

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A Word of Encouragement


Dar al-Hikma


Proclus' Elements


Reversion in the Corporeal


Mathematical Recursion


Episodic Memory




Classical Mortality Arguments


Personal Identity
1   2   3   4  


Existential Passage
1   2   3  


Precedent at Dar al-Hikma


Images of Dar al-Hikma


Passage Types


A Metaphysical Grammar


Merger Probability


Ex Nihilo Probability


Noetic Reduction


Summary of Mathematical Results


Application to Other Species
1   2   3   4  


Potential Benefits


A Dedication


Works Cited

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Chapter 8
Personal Identity

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?
       Philosophers of 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.[1]
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....[2]
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 importance of 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 metaphors.
       Memory's value 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 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....[3]
John Perry clarifies the final sentence of Locke's assertion:

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 mine.[4]
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 remember everything.  Acknowledging this fact, Anthony Quinton[5] and H. Paul Grice[6] have modified Locke's theory to accommodate forgetfulness.  More recently, Perry[7] 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.
       Quoting Sydney 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.[8]
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 which type of memory is necessary for personal identity, and this makes the task a bit more involved.  There are, actually, several known types.[9]  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.
       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 long-term explicit.
       Finally, 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.
       An 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:

Figure 8.1 Fig. 8.1
A taxonomy of memory types[10]

The colored junctures trace the deduction of long-term explicit event memory.

Here we 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.)[11]  And this is where our critique of Proclus' Elements provides a shortcut:
       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, corporeal body.
       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.
       This takes care of the memory criterion.

First Conclusion:   The memory criterion of personal identity has a corporeal basis.

next    Section 2 of 4

Chapter 8, Section 1 Endnotes

[1] Harold W. Noonan, Personal Identity (London: Routledge, 1989) 2.
[2] Paul F. Snowdon, "Personal Identity," Oxford Companion to Philosophy (Oxford: Oxford University Press, 1995) 654-55.  Related texts online.
[3] John Locke, An Essay Concerning Human Understanding, 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.
[4] John Perry, "The Problem of Personal Identity," Personal Identity, ed. John Perry (Berkeley: University of California Press, 1975) 14-15.  Related texts online.
[5] Anthony Quinton, "The Soul," Personal Identity 53-72.
[6] H. Paul Grice, "Personal Identity," Personal Identity 73-95.
[7] John Perry, "Personal Identity, Memory, and the Problem of Circularity," Personal Identity 135-55.
[8] Sydney Shoemaker, "Personal Identity and Memory," Personal Identity 133-34.
[9] A good historical review of the study of mammalian memory can be found in Milner, Squire, and Kandel 445-68.
[10] Milner, Squire, and Kandel 451.
[11] 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). . .
Copyright © 1999

Wayne Stewart
Last update 4/19/11