Derek Parfit makes the bold claim that we can separate the notion of survival from that of continued personal identity. In other words, he claims that in the case of a person dividing into two bodies with exactly similar character and memories, we can say that the person survives the experience without claiming that either of the two resulting bodies is numerically identical to the person who has undergone the division.

Parfit makes this distinction to illustrate that what matters in seemingly unsolvable problems of survival is not continued personal identity, but a form of psychological continuity that is actually the ground for speaking of identity, but whose scope in certain cases extends beyond what counts as continued personal identity. We should therefore abandon the notion in such cases.* This distinction is essential to his proposed solution to the puzzle he presents involving the case of a divided mind, since the notion of personal identity seems to break down when applied such problem cases.

As Parfit points out, normally we not only see survival as a result of continued identity but as equivalent to it (page 204, last par.). Instead, Parfit argues that all cases of continued identity might constitute survival, but not vice versa. In this paper, I will examine Parfit's reasons for denying the equivalence of these two notions and I will evaluate whether this actually provides us with a meaningful answer to the aforementioned case of division.

We may begin by first outlining the initial puzzle, attributed to David Wiggins. I will then define Parfit's key terms and explain first their relation to identity and then their relation to survival, and see if the two do in fact differ. Finally , I will examine whether separating the two solves the problem case.

Parfit proposes we imagine the following scenario: a man's brain is divided into two identical** parts (assuming this is possible). Each part is put into a new body. Parfit assumes that if an entire brain were to be transferred to another body, the person whose brain it was would survive as and be identical to the person with the new body (in such a case the distinction between these two is unnecessary). If we wish to be consistent with this assumption, the case of division has no coherent solution. This is Parfit’s argument for that claim: if we claim that the person does not survive, then it would not have made sense to say he survived the transplant into one body, since each of the resulting bodies would be exactly similar to the one, except in having half as much brain.

Similarly, we cannot say that the person survives as only one of the two, since, again, the two are exactly similar to each other, and there is therefore no reason for believing that the original person survives as one but not the other.

The only remaining solution is to say that the person survives as both, since all the aspects that we counted as important for survival in the case of one new body exist in each of the two new bodies. However, this is logically inconsistent with the notion of numerical identity, which cannot be applied to more than one object or person. For this reason, that is, since asking about personal identity seems to lead to a dead end, Parfit wishes to make survival distinct from continued identity.

Before outlining his arguments for this claim, let us define a few key terms. As already noted, one of Parfit's premises is that "psychological continuity" is essential both to survival and to personal identity. Parfit makes a distinction between this and what he calls "psychological connectedness". However, I will not make that distinction in this paper, since Parfit himself does not do so when dealing directly with the Wiggins case. Instead, we shall use psychological continuity as a blanket term referring to a type of transitive relation that exists between mental properties such as memories and character traits.

The most important distinction in prizing apart identity from survival is between "one-one" and "one-many" relations. Numerical identity is a perfect example of a one-one relation. A thing can only be numerically identical to itself at one time or another, but not to two separate things. On the other hand, one-many relations, as the term suggests, can hold between one thing and more than one other. For example, I can bear a relation of desire to more than one object.

With these terms in mind, we can begin to lay out Parfit's argument. I will show how Parfit defends the following claims about survival and identity, and at the same time show how each applies to the case of the divided mind. First, whereas identity is strictly a "one-one" relation, survival can be either "one-one" or "one-many"; second, although psychological continuity is essential to identity (one of the initial premises)*** and can be a criterion for identity, psychological continuity can exist in cases where there is no continued identity. In these cases, this psychological continuity is more important to our notion of survival than the notion of continued identity; third, although identity is "all or nothing", survival is a matter of degree. This third point is not manifest in the case of the divided mind, so I will not discuss it at great length, but for Parfit it is an essential difference between continued identity and survival.

Parfit thinks Wiggins’ case is proof that survival is not one-one. In fact, he thinks it obvious that the person who is divided survives as both people. He defends this claim by explaining the reasons we have for thinking mistakenly that survival has to be one-one: he points out that since most of the time both identity and survival are one-one, we do not hesitate in equating the two; and, most of the time, this is not a problem. We therefore assign the same properties to identity and survival. Again, this is usually fine, but where it leads us astray is when we begin to think that what matters is the one-one relation itself. Instead, we have to recognize what is behind the notion of identity, and that, Parfit argues, is not necessarily one-one.

This brings us to Parfit's second claim, tied to the notion of what matters to us when we think of survival, regarding the different relations first between identity and psychological continuity and second between survival and psychological continuity. One might argue that, as Wiggins' case shows, continuity cannot be a ground for identity since it is not logically one-one. Parfit responds by saying that when continuity is one-one, it is a perfect way of indicating continued personal identity. However, we again should not confuse what we really think matters with identity. In other words, just because we accept the idea that psychological continuity is a ground for identity, we should not make the jump to thinking it is equivalent to it. He says, "even if psychological continuity is neither logically nor always in fact, one-one, it can provide a criterion of identity...if psychological continuity took a branching form, we ought to speak in a new way, regarding what we describe as having the same significance as identity."(p.,208) In other words, when continuity does not map onto identity, we should remember that what we want is continuity, not identity. A case like Wiggins', therefore, is one of psychological continuity, but not one of continued identity. And since what matters in survival is psychological continuity, we must in this case abandon the notion of identity, as it no longer provides us with criteria that matters.

To sum up these two claims: Identity is always one-one. Wiggins case, since it does not represent a one-one relation, cannot be a case of continued personal identity. However, survival need not be one-one, and the man in Wiggins' situation survives as the two people even though he is identical to neither. This is the first step in making a distinction between identity and survival. Next, what matters in identity is psychological continuity. What matters in survival is psychological continuity. When psychological continuity is one-one, it provides a perfect criterion for identity. When it isn't, it still provides a criterion for survival. So survival covers cases of psychological continuity that are not covered by the notion of personal identity.

To me, Parfit’s arguments for separating identity from survival are so reasonable that I have trouble thinking of sound objections to them. In other words, I think that they provide such a simple, obvious, and intuitive answer to the Wiggins case. For the remainder of this paper, I would like to discuss then why I think they are intuitive, since Parfit does not specifically address that issue.

Suppose I were unversed in the problems of personal identity. Suppose I had never thought about the issues above, including identity and psychological continuity, and I was told that what Wiggins’ operation was going to be performed on me. Suppose further, for the sake of simplicity, that I was told each half of my brain was exactly similar to the other. Moreover, I was told that each half contained all my character and memories. I was told, and believed, that each half of my brain did the same things and that I never realized this because they worked in complete unison.

A philosopher then asked me which of the resulting two people would be me. My immediate reaction would be one of utter confusion, since I had never heard of such a thing happening. Next, I might panic, thinking I was going to die. Finally, though, I would stop worrying, since each body would awaken with the feeling of having survived, and each would remember going into the operation, feeling worried, but now feeling relieved to still be able to think and act as before. Moreover, I would be realize that I felt concern for the future of each of the two resulting people--the same type of concern I feel for myself in the future in normal situations. Thus, the fact that I will have memories of my entire life up the point of the operation in each of the resulting people, the fact that I hope that all goes well for each of the two people in the same way I hope all goes well for me if I don’t have the operation, in addition to the fact that neither of the resulting people is "more" me than the other, would all lead me to the conclusion that I would be both the resulting people.

The philosopher would then say that this is impossible. They would argue that numerical identity, as opposed to qualitative identity, is a relation that cannot hold between an object at time T1 and more than one object at time T2. They would explain that to say I would be both those people is logically incoherent, since the occurrence of "to be" in such a case refers to identity.

My response would then be one of pity for this poor philosopher who defines relations that have no bearing in cases of real life. I would say to him, "You can have your notion of identity, but it makes no difference to me. What I care about is survival, and I know I would survive this operation" In other words, what matters to me are not abstract logical relations, but being able to wake up and take care of my business with the same care and concern I had before the operation.

What would concern me more than the abstract problem of numerical identity would be the practical problems that would arise after the operation. In other words, which of the two "me’s" would live in my house, go to bed with my wife, have to go work, etc. But not only are these practical, not theoretical, problems, but they have an easy solution. I would just think to myself before the operation, "remember, when I wake up, there will be another person around who will lay claim to all my possessions. I must be tolerant of this other person, for he will also be me." This mental note would then exist in both of the resulting individuals, each of whom would understand very well his relation to the other person.

I admit this sounds complicated, and it might require an unusual "intuition," but this is in fact my intuition. My primary point, though, which I think extends to anyone, is that survival is an intuitive notion, one that can, with some effort and stretch of the imagination, extend to such bizarre cases as divided brains. Numerical identity is not intuitive, and cannot be manipulated in any way to solve such problems. In other words, it is an abstract, philosophical term which, moreover, does not work. So when it fails, we should not cling to it to the point of finding ourselves in meaningless paradoxes, but we should instead focus on whatever concrete notions of survival we may have: be they mental, physical, or even spiritual.

In conclusion, any of these three notions of survival will give an answer to Wiggins’ problem that the notion of numerical identity does not. I personally hold a mental view of survival, one that is based solely on memories and intentions, and it is that intuition which I referred to in the imagined dialogue with the philosopher. However, either of the other two would do as well. If one believes that one needs the same physical body over time in order to survive, then Wiggins’ case is death. If, on the other hand, one believes that there is an immaterial "soul" that exists regardless of any mental or physical changes, then the Wiggins’ case has two possible solutions. Either the soul only goes to one body and I survive as that one (how you would figure out which, I don’t know), or the soul would leave the body during the operation, and the person survives in some other realm. My point is that Parfit is absolutely right in separating the notion of survival from that of numerical identity, regardless of what notion of survival one might hold.