The essence of the question at hand is, can I be said to exist over time? This question can be approached in two ways: the metaphysical approach concerns the truth of the statement ‘the me that exists now is the same me that existed in the past’, and the epistemological approach concerns how I can know that the me that exists now is the same me that existed in the past.

This distinction is important because knowledge is not necessarily knowledge of the truth, depending on whether one employs a strong or weak definition of knowledge. A weak definition is the one that we tend to operate with on a daily basis, namely that one has good evidence for a conclusion and none against. A strong definition however, after Descartes, is that it is inconceivable that one could be wrong. This discussion will proceed on the basis that questions of how I exist are too important to operate with a weak sense of knowledge, and that therefore it is the metaphysical question to which I require an answer.

In attempting to reach a conclusion I will consider the theory that my identity consists in my body, that it consists in my psychological states (memories, intentions etc.), and that it consists in a combination of the two. However, as much of the discussion of personal identity takes place around a myriad of thought experiments, I will first consider one that demonstrates the problems inherent in such procedures.

Williams (1973) poses a case in which two people, A and B, are told that a machine is going to effectively swap their bodies; that is, after the procedure, A will find themselves in the body of B, and B in the body of A. They are also told that after the procedure, one will be tortured and the other financially rewarded, and asked which body they would want to be tortured. He surmises, and assumes that we would reach the same conclusion, that A would wish the A-body to be tortured, and B the B-body, which ’seems to show that to care about what happens to me in the future is not necessarily to care about what happens to this body (the one I now have)’. He therefore argues that ‘the only rational thing to do, confronted with such an experiment, would be to identify myself with one’s memories, and so forth, and not with one’s body’.

He then goes on to describe another experiment, in which I am told that I am going to be tortured, but that before this happens my psychological states will be replaced by those of another. In this case, he argues, I will feel afraid at the prospect of the torture, but this is strange as it is merely a one-sided presentation of the previous experiment, so asks, ‘can we really convince ourselves that the second presentation is wrong or misleading, thus leaving the road open to the first version, which at the time seemed so convincing? Surely not.’

It is quite clear, however, that the second presentation is indeed misleading. In the first it is quite simple for me to imagine my psychological states being transferred from one body to another, that someone else’s psychological states are placed in what I had, until that moment, called my body, and that they experience the torture to which it is then subject. In the second presentation, however, I am told that I am to be tortured after undergoing some psychological alteration. If this were restated as “your psychological states will be removed from the body you currently call yours and replaced with those of another” I would have no reason to be afraid of the torture (but would quite possibly wish to inquire as to where my psychological states would then be).

Therefore, one must be cautious in employing thought experiments to determine the nature of one’s identity as they are necessarily cast in language, and language can be misleading. Williams argues that it is not obvious that the ‘use of the second person [has] a rhetorical effect on me, making me afraid when further reflection would have shown that I have no reason to be’; however, just a little further reflection does make it quite obvious.

What, then, of Williams’ conclusion that I should identify myself with my psychological states? The problem with thought experiments does not mean that any conclusion reached through them is therefore invalid, just that it should be cautiously considered. In this case, as I have said, it is quite easy for me to imagine my psychological states being placed in a different body. It is also true that, given advances in medical technology, I can already quite easily conceive of the case in which I have had every part of my body except my brain replaced with that of someone else, but I would still be, as far as I was concerned, ‘me’. It therefore seems quite reasonable to say that my identity does not consist in my body. This does not mean, however, that I should then identify myself with my psychological states; there could be alternatives.

Swinburne’s approach is to argue that one simply cannot pose the metaphysical question (Swinburne 1973), due to the very fact that the main answers to it are those of psychological and bodily continuity. He argues that if it were true that my identity consists in my psychological continuity, it would be logically impossible for me to lose my memory, and that if it were true that my identity consists in my bodily continuity, it would be logically impossible for me to travel from here to there without passing through intervening space (such as by way of a Star Trek-style transporter), neither of which we would wish to concede. That is, these theories rule out the possibility of, respectively, a ‘gap’ in my psychological or bodily ’stream’ of existence.

It is perfectly acceptable to Swinburne that psychological and bodily continuity be taken as evidence of identity (an answer to the epistemological question), however, but he argues that philosophers have attempted to say that they rather constitute identity (an answer to the metaphysical question); that is, bodily and psychological continuity are sufficient for identity. Such a theory he calls empiricist, and argues that it may lead to one of three conclusions about two people: that they are the same, such as me yesterday and me today; that they are different, such as me today and you today; or that there is no clear verdict, such as if a brain was divided and each half placed in a different body.

The consequence of the last conclusion is that empiricist theories will allow for unacceptable situations, such as cases of ‘duplication’, in which two people exist simultaneously who are both the same as an earlier person – such as in the case of a brain divided between two bodies – and this is not a logical possibility. Swinburne correctly argues that a concept of personal identity that can have such a consequence ‘is not recognisably ours’.

The conclusion that Swinburne draws from this is that ‘identity does not consist in the continuity of one or more observable characteristics’. Rather, ‘while evidence of continuity of body, memory and character is evidence of personal identity, personal identity is not constituted by continuity of body, memory and character’. What, then, is personal identity? For Swinburne, it is ’something ultimate’ that ‘cannot be observed apart from observations of continuity of body, memory and character’. He illustrates this by pointing out that, on an empiricist theory, ‘for me to hope for my resurrection is for me to hope for the future existence of a man with my memories and character’, but what we usually mean by this is that I hope that I exist in the future.

Whilst Swinburne is correct that what I am cannot be observed by him, he is not correct that the metaphysical question cannot be asked, for the very fact that I am aware of myself as an “I”, the future existence of which I am concerned for; I can observe myself. Indeed, how could it be the case that I could not ask what it is that I am? It may not be easy to provide an answer, or even possible, but this does not invalidate the question.

Perhaps it would be pertinent, as many of the philosophers considering the question of personal identity fail to do, to consider what my actual experience of being me is like. For example, when I am asleep, sometimes I dream, and sometimes I do not. I would suggest that even this latter case constitutes a ‘gap’ in my psychological continuity, but when I wake I am indeed convinced that I am the same person that went to sleep.

How then, if I perceive the possibility of a gap in my psychological existence, can I know I exist over time? What I am here concerned with is my direct experience; I do not have to try to experience, I simply do. When Swinburne says that personal identity is ’something ultimate’ that cannot be observed other than when it manifests something of itself in bodily and psychological states, he is talking about the observation of personal identity in others, not himself. When it comes to observing myself, I am very aware of my personal identity at that moment; that is, I am me, the same me that I hope will exist in the future when I hope for resurrection.

In his consideration of personal identity, Parfit (1971) introduces the concept of q-memory, in which I have a belief about a past experience that seems to be a memory, such an experience was had by someone, and my belief is dependent on that experience in the same way a memory is dependent upon an experience; that is, a q-memory is something that appears to me to be a memory. He then points out that ‘on our definition every memory is also a q-memory’, so we can ‘drop the concept of memory’.

However, why does a q-memory require that the experience ‘remembered’ was actually had by anyone? Or rather, how would I be able to determine that such an experience was had by anyone? The fact is, I have no reference point to check in what way a memory took place, if at all. A good example are dream memories; if I remember speaking to someone, can I be sure that it took place when I was awake and not asleep? And if I was asleep, could it be said that I did not have the experience, even though it seems very clear to me that I did? The fact is, we do not need to drop the concept of memory, but rather alter its definition to the appearance that I had an experience in the past.

Because, indeed, all I ever have access to are appearances. I experience the world – my body included – only by way of my senses, and this information is available only to me. Further, returning to dreams, it is possible for my senses to be fooled, and so it is conceivable that I am wrong about any, or all, of the “information” they furnish me with. Therefore, even though I can ask it, I cannot answer the metaphysical question: I cannot know, in the strong sense, that I existed yesterday, or that I will exist tomorrow, but only that I appear to exist at this very moment, in some way.

Bibliography

Parfit, D., 1971. The Philosophical Review, LXXX, pp. 3-27

Swinburne, R.G., 1973. The Proceedings of the Aristotelian Society, LXXXIV, pp. 231-47

Williams, B., 1973. The problems of the self: philosophical papers 1956-1972, Cambridge, Cambridge University Press, pp. 46-63