Does personal identity over time consist in some form of psychological continuity?
Submitted for PH144 (Mind and Reality) Summer Exam
![](/img/missing-image.png)
I shall argue that personal identity over time does consist in some form of psychological continuity. I shall consider the possibility that it consists instead in physical continuity, presenting Williams’ argument in, “The Self and the Future” as the strongest version of this case. However, I shall argue that it is misleading because it fails to account for the flow of consciousness, and that transplant cases as made by Locke and Williams himself validate the psychological approach.
The problem of personal identity over time is the philosophical question of specifying necessary and sufficient conditions for person P1 existing at time t1 to be one and the same person as person P2 at time t2. That is, we want some conditions such that in all instances that they are satisfied in respect of two people, those people are numerically identical; and whenever the conditions fail to hold, they are not numerically identical. That is, we want to make explicit the conditions by virtue of which our intuitive grasp that I am the same person I was ten years ago is justified.
One view, held for example by theists, holds that it is by virtue of an immaterial soul which exists in all persons that personal identity over time is defined: I am the same person at these three times because I have the same soul. Others contend that physical continuity is the salient variable, so P1 at t1 is one and the same person as P2 at t2 iff P1 is one and the same human being as P2. The distinction here between a ‘person’ on the one hand, and a ‘human being’ on the other is that the latter is the physical, biological organism, whilst the former is, as John Locke put it, “a thinking, intelligent Being, that has reason and reflection”.
Locke’s own view of personal identity over time is that P2 at a (later) time t2 is the same person as P1 at t1 iff P2 can remember an experience or action of P1’s “from the inside”. He thus holds that it is in virtue of some psychological property that personal identity over time is maintained; in particular, he sees this “memory connectedness” as being the important variable. The view that personal identity consists in psychological continuity is a more general statement of this view, that holds that not only this event memory (remembering events from the inside), but other psychological facts, such as continuity of beliefs, desires, and so on, are what matters.
I shall discard immediately the “soul” view of personal identity, on the basis that there is no evidence that souls exist. Locke further points out that even if they did, this view fails because even if my soul existed before I was born in a different person, there is no sense in which I and the other person are one and the same person. The fundamental contrast therefore is between views (such as the aforementioned “human being” account) that claim that personal identity consists in some physical continuity, and those such as Locke’s that it consists in some psychological continuity.
The intuition for this latter view rests on thought experiments involving transplants, where two people’s minds are swapped; in these cases, our intuition typically favours the primacy of psychological rather than physical facts. These presuppose the distinction between persons and human beings, but I shall not contest this. For instance, Locke imagines the mind of a prince inhabiting the body of a cobbler, so that the person who looks like a cobbler has all the thoughts, inclinations, memories, and so forth, of the prince. He argues that we are minded to feel that this person thereby is the prince, demonstrating that it is some psychological feature by which we make this determination.
As stated, Locke identifies it in particular with the fact that the person in the cobbler’s body has all the prince’s memories, from childhood onwards, that explains that he is the prince. However, since this is subject to numerous, apparently fatal criticisms, such as the problem of absolute forgetting (that I am the same person as I was when I did some action even if I don’t remember it) and the problem of transitivity (that memory is transitive, but identity isn’t), I shall henceforth consider only the more general claim that some form of psychological continuity takes primacy over physical continuity, and set aside the question of if there is a particular psychological feature that is especially salient.
Williams, in a 1973 paper titled, “The Self and the Future”, considers a transplant case more carefully, arguing that it can paradoxically be used to support either the psychological approach or the physical approach. He imagines two men, A and B, who undertake a procedure so that the information in their brains is swapped: so afterwards, the A-body-person has the brain, memories, dispositions, of B and vice-versa. Prior to the procedure, if B were given a choice between, on the one hand, a monetary reward for the A-body-person and torture for the B-body-person, and on the other, torture for the A-body-person and money for the B-body-person, it seems rational for B to choose the former. After the procedure, B, now in A’s body, would be pleased; they receive money, whilst A (now in B’s former body), is being tortured. This suggests, as does Locke’s example, that the psychological approach is correct.
But suppose you, A, had no say in the procedure: your captor simply informed you that he would torture you the next day, but that prior to the torture, total amnesia will be induced in you. Williams holds, reasonably, that it is still rational to fear the torture. But suppose in addition to the amnesia, other mental changes would be induced: your character (beliefs, dispositions, etc.) would alter; you would have false memories. Fear still seems an appropriate response. Now, if we further have that these character traits and memories are appropriate to B, and moreover the process that induces these psychological changes is to copy information from B’s brain to yours, it still seems reasonable to fear torture, because it is you being tortured; this seems to suggest personal identity consists in some form of physical continuity.
This is the strongest argument in favour of physical continuity, but it is misleading. Although the ‘information’ in one’s brain is an important component of what comprises psychological continuity, it fails to account for the actual continuous ‘flow’ of consciousness; although at every stage, A can follow his torturer’s claims, if in fact his consciousness was transported elsewhere – to B’s body – then his fear would abate considerably, knowing that he would never experience the torture. Williams also considers the possibility that the torturer meddled with A, and left B as he is; in fact (assuming still that one is essentially a person, and persons are conceptually distinct from human beings) this scenario corresponds to cloning B, and “killing A”, in the sense that although the biological human being continues, the person is no more; all his memories are gone, anything recognisable by people who knew him is gone, and an ersatz B is instead in his body.
I have considered the possibilities that personal identity over time consists in psychological continuity versus physical continuity, and shown that transplant intuitions as explicated by Locke and Williams demonstrate that (on the assumption that there is in fact a distinction between persons and human beings) the continued existence of a person depends on some appropriate psychological relationship holding between the person at two times. Williams’ later qualification in his thought experiment is flawed because it supposes that copying information from one brain to another is a “mere” psychological alteration, rather than a replacement of one person with habits, beliefs, memories and so forth with another. Hence, it is correct to state that personal identity over time consists in some sort of psychological continuity, though I have discarded as irrelevant for present purposes what particular psychological facts are relevant.