In his article, "The Soul", Quinton invents the following scenario: Suppose he has two friends B and C, each with distinct physical and personal characteristics. One, B, is a "tall, thin, puritanical Scotsman" and the other, C is a "fair, short, plump, apolaustic Pole." We are asked to imagine that one day he sees both these people in a room together. However, all the non-physical traits of B have become C’s and vice versa. Thus, for example, the man who looks like B looked before the exchange has the memories, as well as the accent and temperament, of the man identified as "C" before the exchange. Moreover, each of them is surprised to see what they look like when they look in the mirror, expecting to see the other’s body.

Quinton says there are a number of ways of assessing the situation with regards to personal identity. First, we could say that B and C have exchanged character and memories, implying that the body that looks like B is still identifiable as B, just with a different personality. The same would go for C. This is the "consequence of a bodily crieterion" of personal identity, meaning that personal identity is determined solely by the continuing identity of the physical body. Second, we could say that it is not at all possible to establish identity in terms of the previous identities of the two friends. In other words, we cannot say that either of the two new individuals has the same numerical identity as either of the two individuals before the "exchange". The question of which of these is now B and which is now C would become unanswerable. Finally, there is the alternative for which Quinton argues, namely, that B and C have simply switched bodies. Such is the consequence of the "mental criterion", meaning that personal identity depends entirely on a "series of mental states connected by continuity of character and memory." (page 59 end of 1st paragraph)

Quinton’s arguments supporting this view rely primarily on intuitive notions of identity. He points out the "probable attitude" of people who would be most concerned with the identity of these two people, such as their friends and family members. These people, he argues, would be unlikely to subscribe to the two alternate views of personal identity. They would hesitate either to say either that the man with B’s body is just B with a new personality, or that B had simply ceased to exist. Instead, Quinton says that they would undoubtedly see this as a simple change of bodies. This is based on the idea that we value character and memory and consider particular bodies as relatively unimportant. That is, what makes people "unique" are these personality traits, not particular physical traits.

Quinton admits that we do place some importance on bodily aspects, but that these are unessential to personal identity. So it may upset us if someone whom we cared about "came to have a monstrous or repulsive physical appearance", but this would not affect our willingness to identify this new monster as the same person. In other words, physical traits may help form our opinions of a person, but they are not defining characteristics in the strict sense of the word. Moreover, physical traits may be necessary in picking out a particular person, and if a particular set of character traits and memories were to shift from body to body it might be difficult or even impossible to keep track of this person’s identity, but these would merely be practical inconveniences, and according to Quinton, would have no bearing on personal identity. In the end, our "concern and affection would follow the character and memory complex and not its original associate." (end of page 64) Finally, Quinton says that it is not only others who would continue to identify someone as the same person despite changing bodies, but the person himself would have a consistent view of his own personal identity as he "moved" from body to body.

This view of personal identity based on our intuitions is subject to certain objections. For example, Quinton acknowledges that unfortunately, not everyone considers personality the most important thing in a person. He cites the case of an entrepreneur who takes a lover based solely on her physical appearance. Her personality, one might object, is as secondary to the entrepeneur with regard to his companion as physical apperance is to a man with regard to his best friend.

Quinton gives two responses to this objection, both of which I think are inadequate. First, he says that the entrepeneur will at least take "some note of the character and memories of the companion of his later nights." (bottom of page 65) However, I don’t see why taking "some note" of character traits in this case is any more relevant than someone taking "some note" of physical traits in the previous examples, where Quinton argued that physical traits are entirely unessential to personal identity.

This leads to Quinton’s second response, which says that insofar as the physical traits are separate from the character traits, they only satisfy certain "type" requirements, and do not constitute unique enough characteristics to determine personal identity. In other words, Quinton argues that the aspects required in such phyisical identification could be met by an identical twin. This response is inadequate for a number of reasons. First, it may simply not be true that one is sexually attracted to a particular "type" (as in the case of the entreperneur) but that one is only excited by certain physical aspects that are entirely unique to a particular body. Just as Quinton argues for the necessary character differences in twins who have seen things from differing angles, one could point out very subtle physical differences in the same set of twins: the location of a particular freckle, or even one’s posture or other purely physical mannerism entirely unconnected to character traits.

Secondly, one might make the same observation of "type" requirements for cases where personal identity is based on character. One might say that a man chose a certain friend because he fits certain character "types": he may befriend someone because he fits the type "generous" or "outgoing" or "friendly". It is not inconceivable for someone to befriend someone based solely on these criteria which could manifest themselves in more than one individual.

Quinton says finally that "the relevant complexity of the memories of an individual person is of an altogether different order of mangnitude from that of the bodily properties of an entrepeneur’s lady friend." (Page 66 lines 27-31) However, this complexity seems entirely subjective. In our culture we may value character traits more than physical traits, and we may therefore investigate them more thoroughly, and this may make them seem more complex. But objectively speaking, physical traits are just as complex, and we can easily imagine someone being as scrupulous in characterizing a body as someone else analysing a personality.

In conclusion, Quinton’s arguments seem entirely unsatisfactory for saying definitively that B and C have simply changed bodies, for his arguments are based entirely on subective criteria and the unfounded assumption that character traits are necessarily more "important" than physical traits. In addition he never addresses head on the third alternative that there may be no answer to the question of which is B and which is C. To defend the two alternate view points, let us briefly take two alternate scenarios. First, let us imagine that B and C are two "lady friends" of mine (Chris, these examples may sound funny, but I mean them in all seriousness.) B is a tall, tan blond with large breasts, and I enjoy having sexual relations with her in the outdoors. C, on the other hand, is a more classical beauty, with dark hair, pale skin, and possesses more delicate features. I prefer sexual relations with her indoors. Let us further assume that both these women speak little and that their personality is of little consequence, both to me and to themselves. If one day their personalities were switched, it is not inconceivable for me to see it as a change in personality, not a change in body. A second scenario is even less implausible and provides a more concrete objection to Quinton. Suppose B is the same as in the previous example. C on the other hand, has a body of little consequence, but a wonderful, engaging personality. When I am with B I enjoy purely sexual relations, and I am not interested in any other woman sexually, even if she were to look almost exactly like B. When C and I get together, we spend hours together discussing philosophy and politics, two subjects I hate discussing with anyone else. Suppose that my sexual life and my intellectual life are of equal importance to me. Now suppose Quinton’s switch were to occur in this case: The question of which is B and which is C would become definitively unanswerable. For there would be one woman with the body of B and the personality of C. Hence, one woman would become both a perfect intellectual and sexual companion, who could not be identified as either B or C, but simply as both. There would be another woman, who would be of absolutely no interest to me, who likewise could not be identified as B or C. This woman would not, like the other woman be both B and C, but one could say, very reasonably, that she was neither !