The bodily criterion
Thomas (Janice L.)
Source: Thomas (Janice L.) - Mind and Person in the Philosophy of Religion
Paper - Abstract

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  1. Essential reading – 85
  2. Further reading – 85
  3. Introduction – 85
  4. Identity again — criteria of personal identity – 86
  5. Same body, same person – 87
  6. Necessary and sufficient conditions – 89
  7. What are the limits of 'same body'? – 90
  8. Learning outcomes – 91
  9. Sample examination questions – 91
  10. Tips for answering the sample questions – 91
Full Text
  1. Essential Reading
  2. Further reading
  3. Introduction
    • The first part of this guide covered topics concerned with the metaphysical status of minds. The principal question addressed there was, ‘Is an individual person one substance or two?' The answers considered were:
    • Each of us consists of two substances during this life, one material or physical; the other immaterial or spiritual. At death the physical substance perishes and the true self, the immaterial substance, persists (Section 1, on Substance Dualism, of Part I).
    • Each of us is a solely or exclusively physical being. The subject of experiences is either identical with (reducible to, nothing but) or is supervenient upon a material substance (Section 2, ‘Varieties of anti-dualism and materialism3').
    • A third possibility has been left completely untouched. This is the answer which a metaphysical idealist like Berkeley would give — that there are only spiritual/immaterial substances and that material substance does not exist. (An idealist is one who thinks that only things which are ‘of the nature of an idea' exist.) This has not proved a very widely held view and I do not myself find it at all persuasive so I have chosen — I hope not regrettably — not to give space to a consideration of the idealists' answer.
    • In this part we will look at two questions:
      … What is required for a mind or person to survive change and the passage of time?
      … Could the requirement be met even in a case where the subject suffers death?
    • A good place to start is with the thought that what it takes for a thing to continue in existence for any length of time is that it keep whatever it had to have in order that there be such a thing existing in the first place. So, in the case of persons, you should be able to use any conclusions you have already come to about the metaphysical nature of minds/persons in trying to answer the Part II questions.
    • If you have decided that material substances are the only ones there are, then you will think that a person has to meet whatever are the general conditions that a material thing has to meet in order to persist over time and remain itself.
    • If you believe that a person consists of a material substance somehow joined to an immaterial substance, then you will think that a person must keep the same immaterial substance in order to remain the same person through change and the passage of time.
    • This chapter and the two following will survey the different answers that philosophers have given to the question what it takes for a single person, mind or self to survive through change. Both materialist4 and dualist accounts will be examined critically so that, whatever you take to be the correct view of the metaphysical nature of minds/persons, you will have thought about the sort of persistence persons, so regarded, can possess. Of course, we ought to consider the possibility that a person is not a substance at all, but is rather some other sort of individual. (There will be time to return to this suggestion only very briefly in Chapter 12 of this guide.)
    • Although many would disagree, my view is that survival of death5 (persistence as a single individual person) is a genuine logical possibility (i.e. nothing in logic rules it out) whichever metaphysical account of the nature of persons is accepted.
  4. Identity again — criteria of personal identity
    • The notion of strict, numerical identity6 was introduced in Chapter 6. This is the identity a thing has with itself and can be contrasted with the sort of identity two things — say, two pins — have with one another. If there are two pins, then they are not numerically identical. But they may be so alike that, in common speech, we would call them ‘identical', meaning that they are qualitatively exactly similar: they are ‘as alike as two pins' as the English idiom says.
    • When philosophers write about personal identity it is numerical identity7, not qualitative identity, they mean. But whereas in Chapter 6 it was numerical identity8 at a single point in time that was important, the 'problem of personal identity (which we will be examining here) is the problem of finding what makes a person at one time the very same person as the person encountered at a different time. Sometimes this is described as the problem of discovering the criterion of personal identity.
    • The word ‘criterion' needs some comment. Philosophers sometimes use this word to mean ‘nature', so the criterion of personal identity in this case would be what personal identity consists in - whatever conditions are necessary and sufficient for this person to be the same person as (identical with) one encountered earlier.
    • Sometimes, however, the term ‘criterion of identity9' is used to mean a test that can be applied to discover whether this is a new person or some previously encountered one. A test of identity could be something like fingerprints, but no one thinks what makes you the same person you were is that you have kept the same finger prints. These may tell the world you are still the same person but they aren't what makes or keeps you the same person. You would still be you even if some horrendous accident with acid robbed you of your fingerprints. You should be careful, if writing an examination answer on personal identity, to keep distinct
      … when you are writing and thinking about the nature of personal identity
      … and when you have in mind the evidence or tests which can be used to establish someone's identity.
    • Our main concern here is the nature of personal identity.
  5. Same body, same person
  6. How much of the living body?
    • We live in an era of medical miracles and technological wizardry. Everyone has heard of people whose lives have been extended by kidney, liver, even heart and lung transplants10. It seems that if technology advanced just a bit further, even a brain transplant11 might become possible. Imagine that this has in fact happened — perhaps a pair of accident victims with horrific but complimentary injuries might furnish the first case. Someone called Robinson with irreparable head injuries might receive into his skull the brain of Brown whose torso has been irreparably damaged although his head was unscathed.
    • Suppose someone woke up after this operation, who would he be? Which person would the living survivor of a full brain transplant12 be? Many would answer that the survivor would be the brain donor, Brown. This might appear to go against what we ordinarily say in heart and other organ transplant13 cases where the recipient, not the donor, is held to survive.
    • If you are inclined to agree that in such a science fiction case the brain recipient would not survive, this is probably because you believe that the brain has an overwhelmingly important role in the personal, mental, experiential life of a person. When our survivor woke up, we would expect him to recognise Brown's family and friends and to have Brown's memories, interests, projects and so forth. He would speak Brown's language not Robinson's (if these were different). We would be very surprised if he had any of the memories possessed by Robinson (whom he had never met nor known anything about).
    • After thinking about such a thought experiment14 for a short while, a common response is for a reader or student to conclude that ‘the person goes where his brain goes'. The bodily criterion is really (or should be amended to be) the brain criterion15. (see "Shoemaker (Sydney) - Self-Knowledge and Self-Identity" and "Parfit (Derek) - Reasons and Persons" for more detailed discussions.)
    • But is an entire brain necessary for personal survival? Even when thinking of ordinary cases — not science fiction — we are unlikely to think so. People who have had quite severe damage to one side or the other of the brain (through stroke or accident) can sometimes recover lost functions because the surviving uninjured hemisphere is able to take over roles no longer being performed by the damaged side. And even where a person has severe and unrecoverable deficits of mental function, arguably it is still the original person (not some new one) who survives thus diminished.
  7. Objection to the brain criterion16
    • What if a human brain were to split like an amoeba? Of course, no one imagines that this is about to begin happening in the ordinary course of things. But philosophers have put two ideas mentioned in recent paragraphs together to challenge the brain criterion17 of personal identity.
    • Suppose (what the last-but-one paragraph envisages as true) that a person can survive massive damage to one hemisphere of the brain. Suppose also that transplantation18 of one sound brain hemisphere became medically possible. Then, in principle, it would be possible for two Robinsons (people injured in such a way as to need a new brain to stay alive) to receive help from one Brown (brain donor). If each were given one of the donor's brain hemispheres, each would have a chance of continued life. But who would these two survivors be?
    • The line of thought which said that a brain donor would survive in a single Robinson seems to suggest that the donor would survive twice in the two Robinsons case. The trouble is that such a suggestion flies in the face of a very firmly entrenched principle, the principle of the transitivity of identity. This principle is easy to understand and very difficult to disagree with. It says that things identical with the same thing are identical with each other. If A is B and also B is C then it follows that A is C.
    • So the donor in this case of brain fission we are considering cannot be numerically identical with both of the survivors because his identity with each would mean that each was numerically identical with the other. And of course they cannot be numerically identical with each other because, according to the hypothesis, there are two of them! Something would seem to have gone wrong with the brain criterion19 of personal identity or anyway, our thinking about it. As Derek Parfit20 says, ‘how could a double success be a failure?' ("Glover (Jonathan), Ed. - The Philosophy of Mind", p. 144).
  8. Activity
    • How much of your present living human body do you think you would have to retain, intact, in order to survive as the very person you now are? Could you survive the loss of a limb? More than one? Any internal organs? Of course, if you lost certain organs (your liver, heart, brain) you would die. The question is, could you, the essential person, conceivably survive even loss of life?
    • If it takes the existence of a certain sort of living body in order for there to be a person, perhaps it takes the survival of that very individual body for that individual particular person to survive. So, the question asked by philosophers who think that keeping the same living body is both necessary and sufficient for preserving the personal identity of a particular individual person is ‘what is required in order to remain the self-same living human body?'.
  9. Necessary and sufficient conditions
    • Before exploring a number of possible answers to the last question, it would be a good idea to consider the meaning of the phrase ‘necessary and sufficient conditions'
      which philosophers use such a great deal.
    • A necessary condition of X is one which X could not exist without. Sometimes writers describe such a condition with the Latin phrase sine qua non ('without which not'). There could be no X (whatever it is) if this (necessary) condition did not hold.
    • A sufficient condition (as the phrase implies) is one which is enough to ensure X. If the sufficient condition holds, then X exists.
    • The important thing to realise is that the two sorts of condition are different: a sufficient condition guarantees the obtaining of whatever it is sufficient for, but another alternative sufficient condition could ensure X's existence if the first sufficient condition were absent. For example, if you have to get the votes of a majority out of 99 voters in order to win some election, any 50 voters voting for you will do. There are many possible different combinations of 50 to be found in a crowd of 99. Any 50 are sufficient for your victory. But you do have to get a majority. That is a necessary condition, which has to be met. Even if you do get the majority of the votes, however, you may fail to win if further necessary conditions still need to be met — perhaps there is an age, or nationality, or some other requirement for candidates.
    • Some thinkers believe that keeping the same living body is a necessary condition for personal identity and is also sufficient. Others, who think retaining the same living body is important might think it necessary for personal identity but not sufficient. Still others might think it sufficient but not necessary — for them, there are a number of different ways to preserve personal identity: in the absence of sameness of body; something else (like the psychological continuity21 to be discussed in Chapter 11) might suffice. Yet other thinkers believe it is neither necessary nor sufficient to keep the same body in order to stay one and the same person.
  10. Activity
    • Think about the four possible viewpoints on personal identity just listed. Do you think bodily persistence or continuity is necessary for personal identity over time? Do you think it is sufficient? Both? Neither?
  11. What are the limits of ‘same body'?
    • Imagine that a coin falls under a steam roller and is squashed so that it no longer has the dimensions, or other properties, of a coin. It cannot be used in a shop or vending machine. Now suppose that the lump of metal alloy it has become is taken to the mint and restruck (if this could be done). What should we say about the newly minted coin? Is it the same coin we had before? Or a new coin made from the material which earlier constituted the first coin? (You could look at "Wiggins (David) - Identity & Spatio-temporal Continuity" or "Wiggins (David) - Sameness and Substance", listed in Chapter 11's readings.)
    • Contrast the squashed coin case with the case of a grandfather clock inherited by a grandson who wants to have it refurbished and restored to its former glory. He takes the case to a cabinet maker who disassembles it and, after cleaning and repairing the pieces, restores it ready to be reunited with the works. Meanwhile, a jeweller disassembles, cleans and repairs the clock workings, replaces worn parts and restores the whole to working order.
    • In the coin's history there was certainly a time when there was nothing that looked like or could be used as a coin. In the clock's history there was certainly a time when there was nothing that could have been consulted to discover the time. Should we judge that either, both or neither preserved its identity and stayed a single thing throughout each history I have related?
    • Some writers would say that temporal gaps extinguish identity. The fact that there was a time in the history of the lump of alloy when there was no coin is sufficient to show that two coins are involved — an earlier and a later — with no single coin preserving its identity throughout. On the other hand, it may seem less plausible to say that there is not a single grandfather clock in the story of clock and case disassembly and repair. There may have been a time when there was no clock to be used as a clock, but there seems not to have been a time which could be described as a gap in the clock's existence. It might be held that it survived (disassembled) the time when it was being restored. Indeed, the grandson would be angry if he thought he was being given a new clock after the restoration. His hope and intent were to have the old one (that very clock) restored.
    • Now, consider the view that keeping the same body (bodily continuity)22 is essential to personal identity — that it is both necessary and sufficient for personal identity. Consider also the question whether a human body could survive a temporal gap — a time when that body did not exist. Could a living body be genuinely one and the same person as an earlier person if that body had suffered death in between the earlier and later times?
    • Some thinkers would say that death constitutes a temporal gap, a time during which the body ceases to be the same (living) body as before. Such writers would invoke the analogy of the squashed coin and say that, however similar any later living body might be to some earlier one whatever agency (even God) was responsible for reassembling and injecting life into the constituents of that body; however swiftly after death the recreation of the body took place; nevertheless, temporal gaps extinguish identity. Once something has gone out of existence, however briefly, any later thing, however similar, is a replica of (and numerically distinct from) the earlier thing, not a continuation of it.
  12. Activity
    • Reconsider the four possible positions on the importance of bodily continuity23 to personal identity. Is death more like disassembly, or destruction? Another way to put this question might be, ‘is death, in principle, a reversible process or an irreversible one?' If you melt, and then refreeze, some frozen water, do you finish up with the same ice cube or a new one?
  13. Learning outcomes: After studying the material in this chapter you should be able to:
    • Explain the nature of the philosophical problem of personal identity over time.
    • Discuss the difference between two senses of the phrase ‘criteria of personal identity'.
    • Outline what the principle of the transitivity of identity says and how the notion of transitivity can be used in an argument against the view that personal identity is just brain identity.
    • Use correctly the phrases ‘necessary condition' and ‘sufficient condition'.
    • Present, explain and criticise the support that a defender of the bodily criterion would give for the view that keeping the same body is either necessary or at least sufficient for personal identity.
  14. Sample examination questions
    • If I am, after resurrection, to be the same person as my pre-mortem self, must I get my old body back? Is it possible to do so: even if I were given a body made of just the same matter, arranged in exactly the same way, would that be the same body?
    • Do temporal gaps extinguish identity? For persons as well as simple material objects?
  15. Tips for answering the sample questions
    • These two questions are really asking essentially the same thing. The second asks you, very directly, to consider whether persons are simply and straightforwardly material objects. It would be advisable to give some time to this question in an answer to the first sample question as well. You should also discuss the suggestion that death creates at least a temporal gap in the identity of a living body and that temporal gaps extinguish identity.


Part 2 (Personal identity and survival of death)24; Chapter 10. Hard Copy in "Various - Papers on Religion Boxes (Heythrop)".

In-Page Footnotes

Footnote 1: The Guide actually suggests Defending the Soul, 1992. In "Ward (Keith) - The Battle for the Soul", Chapter 7 is “The Soul and the Brain”, which is probably substantially the same as Chapter 8 in the recommended book. Both are probably superseded by "Ward (Keith) - More Than Matter: Is Matter All We Really Are?".

Text Colour Conventions (see disclaimer)

  1. Blue: Text by me; © Theo Todman, 2021
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