A natural first thought about how we might answer the question raised by The Return of Martin Guerre is this: The man who returns many years later is the same person as the one who left earlier just in case the returning man can remember things that happened to the earlier
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stage. This point requires an immediate clarification. We might seem to remember things that did not in fact happen to us. For instance, my daughter once was convinced that she and I had once seen a bear out-side of a doughnut shop, and she talked about the “memory” frequently.
However, I’m certain that I’ve never taken her to a doughnut shop, much less seen a bear outside of one. My guess is that she had a vivid dream in which this bear sighting happened, and then later she mistook it for a memory.These things are not uncommon. Cases of this kind I shall call apparent memory to distinguish them from genuine memory.This distinction allows us to clarify our earlier hypothesis as follows:
Diachronic personal identity theory 1: Person stage P1is a stage of the same person as person-stage P2 if and only if P2 can genuinely remember experiences had by P1.
As it turns out, the later person-stage only apparently remembers experiences had by the earlier person-stage of Martin Guerre. The man who returns to the village is an imposter who had befriended the real Martin abroad and learned so much about him that he decided to attempt to stand in for him back in Martin’s village. Unfortunately, the real Martin eventually shows up back in the village and unmasks the imposter, who is hanged for his impersonation. That series of events comports with our diachronic theory 1 above, for the imposter who comes to the village only seems to remember experiences had by the earlier person-stage, but does not genuinely remember them.
This theory also makes good sense of John Locke’s famous case of the prince and the cobbler.3Modifying the case for present purposes, imagine a prince whose brain and other parts of his central nervous sys-tem have been transplanted one night into the body of a cobbler; a sym-metrical operation has been performed on the cobbler. Here it seems very plausible that the prince wakes up with the body of a cobbler, and the cobbler with the body of the prince. One might explain that fact by noting that the later person-stage of the prince, waking up in the cob-bler’s bed, can remember experiences had by the earlier person-stage of the prince surrounded by courtesans. Likewise the later person-stage of the cobbler, waking up in the prince’s bed, can remember experiences had by the earlier person-stage of the cobbler surrounded by the tools of his humble trade. It seems that both the prince and the cobbler have had “body transplants” while retaining their central nervous systems.
3Locke, J. Essay Concerning Human Understanding, edited by P. Nidditch. Oxford:
Oxford University Press, 1975, p. 30.
This diachronic theory of personal identity over time is due to Locke and is sometimes referred to as a form of psychological continu-ity theory. It is not without its detractors. For instance, the Scottish philosopher Thomas Reid (1710–96), writing a century after Locke, challenged Locke’s very reliance on psychological continuity as the deciding factor. Reid first suggests that while psychological continu-ity might be evidence of personal identcontinu-ity over time, it is not what makes for such identity over time. Locke, I’m sure, would not be ter-ribly bothered by this challenge and would want some evidence for the claim. Reid gives just this, writing,
Although memory gives the most irresistible evidence of my being the identical person that did such a thing, at such a time, I may have other good evidence of things which befell me, and which I do not remem-ber: I know who bare me, and who suckled me, but I do not remember these events. (Essays on the Intellectual Powers of Man,Cambridge, MA: MIT Press)
I cannot remember being nursed by my mother at age six weeks, though she assures me that I did nurse at this age. Surely, though, I am the same person as the one who was nursed by her those many years ago. Further, even if you doubt that I was a person as an infant, the same point applies to any experiences, at a tender age or not, of which I have no memory for whatever reason.
Reid poses a good challenge to Locke’s psychological continuity theory, but that theory has the resources to respond to it, for we may weaken the theory while retaining its spirit. Perhaps I cannot remem-ber things that befell me when I was a young child. However, I can remember things that befell earlier person-stages, who could remem-ber things that befell earlier person-stages, who could rememremem-ber things that befell . . . all the way back to experiences had by the young child.Thus whereas Locke’s original diachronic personal identity the-ory 1 suggests a picture like this:
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Person-stage P1 Person-stage P2
Memory Links
Figure 4: An Illustration of Diachronic Personal Identity Theory 1
A revised version of that theory would suggest a picture like the following:
P1 P2 P3 PN-2 PN-1 PN
Figure 5: An Illustration of Diachronic Personal Identity Theory 2
where, as in Figure 4, all the arrows represent memory links. Here, so long as there are a finite number of person-stages between PNand P1, each of which can remember the preceding person-stage, then PNand P1are stages of the same person. Further, you can slice things as finely as you like, so that two adjacent person-stages are only a few moments apart from one another.
A little reflection shows that this modification is required to save Locke’s theory from inconsistency even leaving aside Reid’s objection.
For imagine an old general (OG) who recalls his bravery on the battle-field as a young captain (YC). The young captain in turn remembers stealing apples from a neighbor’s tree as a little boy (LB).4According to Locke’s theory, OG is one and the same person as YC, and YC is one and the same person as LB. Further, identity generally, and personal identity specifically, seem to be transitive; that is, if A is the same person as B, and B is the same person as C, then A is the same person as C. Hence it just follows on Locke’s theory that OG is the same person as LB. His origi-nal theory denies this (since OG does not remember experiences had by LB). Hence it requires a modification such as the following:
Diachronic personal identity theory 2: Person-stage P1is a stage of the same person as person-stage PN(where N is finite) if and only if PNcan gen-uinely remember experiences had by person-stage PN–1, which can remember experiences had by person-stage PN–2, which can remem-ber. . . which can remember experiences had by person-stage P1. Figure 5 above illustrates this theory, which accounts for the old gen-eral case, as well as permitting Locke a cogent reply to Reid. However, we are not yet out of the woods. For although diachronic personal
4This example is drawn from J. Perry, “Introduction,” in Perry, ed., Personal Identity. Berkeley: University of California Press, p. 17.
Memory Links
identity theory 2 improves upon the earlier theory it is still not ade-quate. First of all, consider Lenny from the movie, Memento. Lenny has had an accident resulting in a severe form of amnesia known as anterograde amnesia. Although he can recall things from before the accident, he literally can’t make new memories. In one chase scene in the movie, for instance, he can’t even remember whether he is chas-ing the other guy or the other guy is chaschas-ing him! In spite of havchas-ing tattooed various statements onto his skin, he cannot be sure whether the person-stage that tattooed those statements had his facts straight.
Consider two person-stages of Lenny existing after the accident.
Because of the severity of his amnesia, these two stages cannot be connected along the lines of diachronic personal identity theory 2.Yet it seems clear that they are two stages of the same person. Can you think of a way of changing the letter while retaining the spirit of diachronic personal identity theory 2, in order to deal with the puz-zling case of Lenny?