closest continuer, closest predecessor and the quandary of overlap situations

robert nozick'in "en yakın takipçi" kuramını sunar: [ardından da düşüncenin tartışmasını içeren düşünce deneylerini özetledim efem]

personal identity through time, robert nozick; in personal identity; ed by raymond martin and john barresi, blackwell publishing, 2005 p92. (from: Robert Nozick, "Personal Identity through Time" pp.48,50-1,58-61, and 69. Cambridge, Mass.: The Belknap Press, imprint Of Harvard University Press, 1981.)

To be something later is to be its closest continuer.

The closest continuer view helps to sort out and structure the issues; it does not, by itself, answer the question. For it does not, by itself, tell which dimension or weighted sum of dimensions determines closeness rather, it is a schema into which such details can be filled.
The nature and contours of people's responses to the puzzle of the ship fits the closest continuer schema and supports it, if not as a metaphysical truth then at least as a component of a psychological explanation of these responses.

The closest continuer view presents a necessary condition for identity; something at t2 is not the same entity as x at t1 if it is not x's closest continuer. And "closest" means closer than all others; if two things at t2 lie in closeness to x at t1, then neither is the same entity as x. However, something may be the closest continuer of x without being close enough to it to be x. How close something must be to x to be x, it appears, depends on the kind of entity x is, as do the dimensions along which closeness is measured.

If persons conceivably can transfer from one body to another, still, bodily continuity can be an important component of identity, even (in some cases) its sole determinant. The dimension of bodily continuity can receive significant weight in the overall measure of closeness for persons.
To say that something is a continuer of x is not merely to say its properties are qualitatively the same as x's, or resemble them. Rather it is to say they grow out of x's properties, are causally produced by them, are to be explained by x's earlier having had its properties, and so forth.

[not sameness but a kind of continuity: ]

This causal dependence, however, need not involve temporal continuity. Imagine that each and every thing flickers in and out of existence every other instant, its history replete with temporal gaps. (Compare how messages are transmitted on telephone wires.) According to concepts developed later in this chapter, if every thing leads this mode of existence, then it is the best kind of continuity there actually is, so all such will count as continuing objects.

temporal gaps are plausible: what is important is rather which is the best situated in relation to the original

[continues along piaget’s experiments, an objects disappears behind a screen and another appears after a time interval, people tend to believe that this was the former one, but then when two objects appear? which one is the continuer?]

... quandary about temporal overlap is intrinsic, I believe, to any notion of identity applicable to more than atomic-point-instants. Any such notion trades off depth to gain breadth; in order to encompass larger entities, it sacrifices some similarity among what it groups together. Maximum similarity within the groupings would limit them to atomic-point-instants. The purpose of the identity notion is wider breadth, but a grouping that included everything would not convey specific information. The closest continuer theory is the best Parmenides can do in an almost Heraclitean world.

The notion of identity itself compromises between breadth and (exact) similarity (which similarity can include being part of the same causel process). Since spatial and temporal distances involve some dissimilarity any temporal or spatial breadth involves some sacrifice of (exact) similarity. For our cases, width and breadth are measured along spatiotemporal dimensions, closeness or similarity along other dimensions. The informativeness of a classification varies positively with the extent of its sub-classes, and with the degree of similarity exhibited within each subclass; similar norms apply to the clumping of entities from the flux.

The alternative to a closest continuer schema is Heraclitean flux, down through all levels, if it becomes legitimate, because necessary, to use the schema at some low level then why not simply begin with it?

[closest predecessor and mono-relatedness:]

In addition to the closest continuer, we also must focus on the closest predecessor, for similar reasons. Something y may be the closest continuer of another thing x even though x is not y's closest predecessor. Though nothing at t2 more closely continues x than y does, still, y more closely continues z at t1 than it does x at t2). For a later stage y to be part of the same continuing object as an earlier stage x, not only must y be the closest continuer of x, also x must be the closest predecessor of y. Let us say that two things or stages so related are mono-related. This mono relation need not be transitive, since neither closest continuer nor closest predecessor need be transitive.

How shall a view of identity over time cope with these nontransitivities of mono-related, closest continuer, and closest predecessor? Let X refer to the entity over time that continues x at t1. I see the following four possibilities.

1. Entity X follows the path of closest continuation.... Entity X is constituted from moment to moment by the closest (and close enough) continuer of the immediately preceding component of X....
2. Entity X follows the path of closest continuation, unless it is a short path. If a tn+1 is reached when there is no continuer of the component at tn of X, then backtracking occurs to the nearest component C of X for which there exists at tn+1 something z which continues C closely enough to be (identical with) it. The component at tn+i of X is then z, and X continues from z on the path of closest continuation. At tn+i, there is a "jump" to the segment of the path that z begins.
3. This alternative is like the preceding one, except that between the lime of C and tn+1, the components constituting X are some continuation path of C that leads to z, without jumps. (Each succeeding step from C will be to a continuer, but not all will be to an adjacent closest continuer.)
4. Entity X originates with x at t1 and each later component of X is the j closest continuer existing at that time of the original x at t1. Since everything harks back to x at t1 there may be considerable hopping, either around or back and forth.

[thought experiments:]

[application of closest continuer to theseus' ship problem:]
The planks of a ship are removed one by one over intervals of time, and as each plank is removed it is replaced by a new plank. The removal of one plank and its replacement by another does not make the ship a different ship than before; it is the same ship with one plank different.
Over time, each and every plank might be removed and replaced, but if this occurs gradually, the ship still will be the same ship.

It is an interesting result, but upon reflection not so very surprising, that the identity of something over time does not require it to keep all the very same parts. It turns out that the planks removed had not been destroyed but were stored carefully; now they are brought together again into their original shiplike configuration. Two ships float on the waters, side by side side. Which one, wondered the Greeks, is the original?

In the case of the ships, there are two relevant properties: spatiotemporal continuity with continuity of parts, and being composed of the very same parts (in the same configuration).
If these have equal weight, there is a tie in closeness of continuation.

Neither, then, is the closest continuer, so neither is the original ship. However, even when the two properties receive equal weight, if there actually had been one ship existing without the other, then it, as the closest continuer, would be the original ship. Perhaps the situation is not one of a clear tie, but one of an unclear weighting.

[so he goes on to the defects of our powers of understanding..] 0ur concepts may not be sharp enough to order all possible combinations of properties according to closeness of continuation. For complicated cases we may feel that which is closest is a matter to decide, that we must sharpen our concept to settle which is (identical with) the original entity. It is different, though, with persons, and especially with ourselves; we are not willing to think that whether something is us can be a matter of (somewhat arbitrary) decision or stipulation.
yet the problem on a closer look seems to appear only after the second ship’s appearance

[questions about beaming:]

[nozick transfers from williams:]
We are prone, otherwise, to think that a person could enter a machine, disappear there, and appear in another machine ten feet to the left, without ever having occupied any intervening space. Williams asks us to imagine that there also had been an additional machine ten feet to the right, and at this one too had appeared simultaneously another (qualitatively) identical being. Neither of the two then would be that original person who entered the machine in the middle. Furthermore, if in that situation of double materialization, the person on the left is not the original person, then neither is he in the different situation where only one person appears on the left. The mere possibility of someone also emerging (discontinuously) on the right is enough, according to Williams, to show that anyone who emerges (discontinuously) on the left, even if all alone, is not the original person.

[beaming:]
Consider the mode of long distance travel described in science fiction stories, wherein a person is "beamed" from one place to another. However, the person's body does not occupy intermediate places. Either the molecules of the decomposed body are beamed or (truer to the intent of the stories) a fully informative description of the body is beamed to another place, where the body then is reconstituted (from numerically distinct molecules) according to the received information. Yet the readers of such stories, and the many viewers of such television programs, calmly accept this as a mode of travel. They do not view it as a killing of one person with the production of another very similar person elsewhere. (We may suppose that those few who do view it that way, and refuse so to "travel", despite the fact that it is faster, cheaper, and avoids the intervening asteroid belts, are laughed at by the others.) The taking and transmission of the informative description might not involve the de-materialization of the person here, who remains also. In that case, the newly constituted person there presumably would be viewed as a similar duplicate.

[beaming overlap:]
Do we need to stipulate that the process of transporting by beaming by its nature, must involve the dematerialization of the original here? In the case of people, at least, a merely accidental ending of the person here may seem inadequate for continuation there; consider the case where as the information is beamed to create what is intended to be only a duplicate the original person is shot, so that (to speak neutrally) the life in that body ends. Yet, imagine a beamer which can work either way - dematerializing here or not - depending upon which way a switch is thrown. If the process with dematerialization is far more expensive, might not those who wished to travel there choose the less expensive method combined with an alternative ending (accidental with respect to the transporting process) of their existence here? I shall leave these issues unresolved now.

[cases with duplication and (half)-brain transplantation:]

[Case 1] duplicating: After precise measurements of you are taken, your body including the brain, is precisely duplicated. In all physical proper ties this other body is the same as yours; it also acts as you do, has the same goals, "remembers" what you do, and so on.
Intuitively, we want to say that you (continue to) exist in this case, and also that a duplicate has been made of you, but this duplicate is not you. According to the closest continuer theory, too, that other entity is not you, since it is not your closest continuer.

[Case 2] brain transplant: You are dying after a heart attack, and your healthy brain is transplanted into another body, perhaps one cloned from yours and so very similar though healthier. After the operation, the "old body" expires and the new body-person continues on with all your previous plans, activities, and personal relationships.
Intuitively we want to say, or at least I do, that you have continued to exist in another body. (We can imagine this becoming a standard medical technique to prolong life.) The closest continuer theory can yield this result. The new body-person certainly is your closest continue With psychological continuity and some bodily continuity (the brain is the same), is it a close enough continuer to still be you? I would say it is.

[Case 3] mind pattern transfer: As you are dying, your brain patterns are transferred to another (blank) brain in another body, perhaps one cloned from yours. The patterns in the new brain are produced by some analogue process that simultaneously removes these patterns from the old one. (There is a greater continuity - or impression of it - with an analogue process as compared to the transmission of digitally coded data.) Upon the completion of the transfer, the old body expires.
[he still believes that that could be me, although there need be no physical continuity at all]

[Case 4] half brain transplant: Suppose medical technology permitted only half a brain to be transplanted in another body, but this brought along full psychological similarity.
If your old half-brain and body ceased to function during such a trans plant, the new body-person would be you. This case is like case 2, except that here half a brain is transplanted instead of a full one; we are imagining the half-brain to carry with it the full psychology of the person.

[Case 5] half brain dead: Suppose that after an accident damages a portion of your brain, half of it is surgically removed and ceases to function apart from the body. The remaining half continues to function in the body, maintaining full psychological continuity.
Although half of your brain has been removed, you remain alive and remain you.

[Case 6 (4+5)] half brain transplant with overlap: Let us now suppose the fourth and fifth cases are combined: half of a person's brain is removed, and while the remaining half-brain plus body function on with no noticeable difference, the removed half is transplanted into another body to yield full psychological continuity there. The old body plus half-brain is exactly like the continuing person of case 5, the new body plus transplanted half-brain is exactly like the continuing person of case 4. But now both are around. Are both the original person, or neither, or is one of them but not the other?
It appears that the closer continuer in case 6 is (the person of) the original body plus remaining half-brain. Both resultant persons have full, psychological continuity with the original one, both also have some bodily continuity, though in one case only half a brain's worth.
If this one is closer, as appears, then he is the original person and the other is not. True, it feels to the other as if he is the original person, but so did it for the duplicate in the very first case. Still, I am hesitant about this result. Perhaps we should hold that despite appearances there is a tie for closeness, so neither is the original person; or that though one is closer to the original person, close enough to him to constitute him when there is no competitor (as shown by case 5), that closer one is not enough closer than the competitor to constitute the original person. On this last view, a continuer must be not only closest and close enough, but also enough closer than any other continuer; it must decisively beat out the competition.

[Case 7] Improbable random event (note that this is different from re-creation or beaming): As you die, a very improbable random event occurs elsewhere in the universe: molecules come together precisely in the configuration of your brain and a very similar (but healthier) body, exhibiting complete psychological similarity to you.
This is not you; though it resembles you, by hypothesis, it does not arise out of you. It is not any continuer of you. In the earlier cases, by psychological continuity I meant "stemming from" and "similar to". Of course, we can have the first without the second, as when drastic changes in psychology are brought on by physical injury or emotional trauma; case 7 shows the second without the first.

[Case 8] half brain transplant and temporary overlap: Half of an ill person's brain is removed and transplanted into another body, but the original body plus half-brain does not expire when this is being done; it lingers on for one hour, or two days, or two weeks. Had this died immediately, the original person would survive in the new body, via the transplanted half-brain which carries with it psychological similarity and continuity. However, in the intervening hour or days or weeks, the old body lives on, perhaps unconscious or perhaps in full consciousness, alongside the newly implanted body.
Does the person then die along with it (as in option 1 above)? Can its lingering on during the smallest overlapping time interval, when the lingerer is the closest continuer, mean the end of the person, while if there was no such lingerer, no temporal overlap, the person would live on? It seems so unfair for a person to be doomed by an echo of his former self. Or, does the person move to the new body upon the expiration of the old one (as in option 2 above)? But then, who was it in the new body for the hour or two days or two weeks preceding his arrival there, and what happened to that person?
...the closest successor of A is B, and the closest successor of A + B is D. However, the closest predecessor of D is C, and the closest predecessor of C + D is A. Neither A + B + D nor A + C + D is a mono-related entity. Taking a longer view, though, A and D are mono-related: D is the closest successor of A plus A's closest successor; also A is the closest predecessor of D plus D's closest predecessor.

A.............B
................C......................D

long-short overlap: If the old body plus half-brain linger on for long enough, three years say, then surely that is the person, and the person dies when that body expires - the duplicate does not suddenly become the person after three years. A one-minute period of lingering is compatible with the new body-person being the original person, a three-year period is not.
[this may be explained by mono-relatedness, but the overlap situations will remain problematic:]
When B and C are small in comparison, the mono-relation of A and D would seem to constitute them as part of the same entity. Thereby, is marked off an extensive entity. Are we mono-related entities that need not be temporally continuous? On this view, there could be a person with temporal parts A and D during times 1 and 3, yet that person does not exist during the intervening time 2. Something related does exist then, so this discontinuous person does depend upon some continuities during time 2, but these are not continuities through which he continues to exist then. (A watch repairer takes a watch completely apart and puts it together again; the customer later picks up his watch, the same one he had brought in, though there was an intervening time when it did not exist.)
[problems concerning law and ethics:]
This view encounters difficulties, however. C might think to himself, "Since it is unjust for someone to be punished for a crime he did not do, D may not be punished for a crime planned and executed during time 2, when D does not exist. No one will be apprehended until time 3, so it is safe for me to commit the crime without fear of punishment." Surely we may punish D for what C does. Is it B or C we punish for the acts of A? Or do we wait until time 3 and punish D? (Yet, if D certainly will escape punishment if we wait, do we punish B or C?) It would appear that D may not be punished for acts of B (unless C does not exist). However, B might assassinate a rival political candidate to bring about the election of D. If this continued a calculated plan put into effect by A, then D may be punished; but suppose B first thinks of this act during time 2, or that A planned it thinking his life would end with B, in order to ensure that the later person D who claimed to be A - falsely on A's view -would be punished for usurping A's identity. It is clear that a morass of difficulties faces the position that one continuing entity includes A and D as parts but not the overlapping segments B and C.