by Neusa Facenda
April 2010

Perry’s A Dialogue on Personal Identity and Immortality gives an example of logical thinking and argumentation. More than theorizing, this text expresses ways of defending ideas and proving them to be true or more-likely-to-be-true than other ideas. The four theories of personal identity—body theory, soul theory, memory theory, brain theory—expressed in Perry’s book are well discussed. In a general sense, it seems that the body theory wins the round of dialogs for having more pros and fewer cons than the soul, memory, and brain theories. It follows then that survival after death would not be possible, because when the body dies the person’s identity ceases to exist. Let it be noted that none of the theories was definitely proven flawless. Although a lot of arguments exist against the memory theory, I believe personal identity is directly related to a person’s memories, which helps to shape a person’s psychological personality. In order to prove my position, I will argue in favor of the memory theory by introducing a new argument, and later by comparing it to the other theories.

Despite arguments against the memory theory, it is still the strongest single characteristic of a person’s identity. Memories are not comprised only of “who did I have dinner with yesterday?” or “I remember to have had red wine last week.” Memories are the major mechanism for our behavior, mannerisms, feelings, and attitudes regarding particular situations. The formation of one’s psychological behavior involves memories. The shy smile of somebody recognizing a neighbor, the warm smile of somebody greeting a good friend, and the sadness of somebody that misses someone special are all reactions that are brought about by memories. One person recognizes another not only by physical characteristics, but also by the combination of accumulated memories, which provides common things to share and talk about.

Now let us consider memory loss. If I lose my memories, do I stop being me? No. There are conscious and subconscious memories. Conscious memories lead us to the type of interaction expressed by statements like, “Let us go to that restaurant where we went last week, because the food was great.” This type of memory allows people to identify themselves to one another by common interests and shared experiences. However, if somebody loses (partially or completely) those conscious memories, there are still subconscious fragments that will make one laugh in the same old way, walk in a certain way, or hold the fork and knife in certain position; these behavioral characteristics are integral parts of one’s personal identity. My father laughs very loudly and in a particular way when he is happy, especially after a glass of good wine, which he appreciates. I could recognize his laughter without looking at him; if I just listened I could tell, “This is definitely my dad laughing!” The major evidence for subconscious memory comes from the fact that the great majority of individuals still know how to hold a fork, how to speak, how to write, and so on, after experiencing memory loss. People perform these tasks without thinking about them. However, speaking, eating, and writing are not inherited traits; they were all learned at some point, and therefore, they are part of memory. I have never heard of somebody who had their penmanship completely modified after memory loss—people tend to draw the letters in a certain way regardless.

Every individual presents a unique combination of what I call “subconscious memory-related qualities” that makes up their personal identity. In the case of certain conditions, such as Alzheimer’s, personal identity disappears with the progression of the disease, and therefore, the individual that was there before ceases to exist. The resulting individual is someone with no capability of retaining any memories of any kind, and is therefore a person without identity.

If we compare the memory theory as I have just described it and the body theory, according to which “I am my physical body” (Perry 1978: 36), we can see that now the body theory does not make much sense anymore. The physical body may be one of the means by which we can recognize a person; nevertheless, it is not sufficient to characterize each person’s unique identity. A blind person can recognize friends and family. This recognition is not only based on physical factors such as voice, but also on the way a person uses voice to express thoughts, feelings, and so on. A blind person may be able to recognize when a close friend is excited, worried, or lying. This recognition does not come from a particular way the body moves, but by the unique behavior that is expressed and repeated to a point that the memory can identify it. For example, plastic surgery is very advanced nowadays—let us consider that a person can be modified as to be exactly like me, having the same facial characteristics, body type, even the same voice, but not the memories that make up my personality. That person is not me, and ultimately will not even sound like me because she will not use the same accented intonation or word choice that I would. Therefore, body is not sufficient to define one’s personal identity.

Regarding the soul theory, in which an immaterial soul defines personal identity, the argument is sufficient to discard this theory as determinant of personal identity. In A Dialogue on Personal Identity and Immortality, Weirob argues that souls cannot be seen, or touched, or smelled (Perry 1978: 8); nevertheless, we cannot know when a soul is present or not. Unless there is a way of confirming the existence of a soul by any sort of technology or study, I do not see how this theory could be proven. Therefore, the memory theory is better to define personal identity than the soul theory.

The brain theory is more difficult to argue because the memories of a person are linked to that person’s brain. In other words, the brain harbors the memories that are responsible for the psychological qualities that define one’s personal identity. The brain theory is a modified argument that is intended to replace the memory theory; moreover, we can raise some good arguments against the memory theory by using brain theory principles. However, I refuse to believe the identity of a person can be described as “I am my brain, and where my brain goes I go with it” as in the case of the Julia North thought experiment (Perry 1978: 38). Therefore, I’ll try to defend the memory theory from it the best I can. For example, let us say that a brain copy is possible, and that my brain is exactly copied with all the memories it contains. One can say that a body from another individual combined with my brain and all my conscious and subconscious memories would be me. It seems logical that if I defend the memory theory I should agree with this statement. Nevertheless, a physical brain may contain one’s psychological behaviors and thoughts within it, but the body that this brain will be transferred to may contain different synapses. In other words, the way the brain communicates with or sends signals to the body is different from person to person. Therefore, all the mannerisms, voice articulations, and other signs of subconscious memory-related qualities would be gone, and the resulting person would not be me. The resulting person may remember having had red wine last week and liking the tagliatelle al ragu, but this person would only seem to be me. The body would not respond to stimuli the way my own would, therefore it would not be me. The resulting person may not like pasta because of differences in taste buds. Also, this person may never be able to talk, walk, laugh, or express emotions the same way as I would. Therefore, the memory theory alone is still better than the brain theory to define personal identity. And after this discussion, we may add that the memory theory has to be related to the same physical connection that translates ones memories into reactions.

Unfortunately, the memory theory is not compatible with the idea of human immortality. The only way the memory theory would work in terms of giving hope for survival after death is if it was combined with the soul theory. We could say that if the memories were linked to an invisible force capable of leaving our body after death and continuing living in a parallel world (or heaven), than survival would be possible. On the other hand, this invisible soul would have to be linked at all times with the same physical connections coming from the same physical body that sustains the memories; but we cannot know if the soul is there because we cannot see it. It does not work. Memory theory does not give hopes for survival after the death of the body.

Overall, none of the theories are flawless. We could argue against the four theories by using all sorts of hypothetical scenarios. However, I believe the memory theory, as I have described earlier, is the best way to define personal identity.


Perry, John. A Dialogue on Personal Identity and Immortality. Indianapolis: Hackett, 1978. Print.

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