Sydney Shoemaker attempts to reconcile the notion of personal identity with a materialist account of the mind. However, when faced with admittedly unusual yet still conceptually possible scenarios, the theory of psychological continuity leads to confusion and fails to provide us with satisfactory answers.
In Personal Identity,Sydney Shoemaker attempts to reconcile the notion of personal identity with a materialist account of the mind. To this end, he introduces the concept of psychological continuity: namely, that a person's identity consists of the direct connection of successive person-stages through psychological phenomena such as memory impressions and personality traits. Where other materialist accounts of identity seem strained at best and inconceivable at worst, this account retains a certain plausibility when applied to everyday experience. However, when faced with admittedly unusual yet still conceptually possible scenarios, the theory of psychological continuity leads to confusion and fails to provide us with satisfactory answers.
Shoemaker introduces the theory of psychological continuity as an improvement upon the theory of memory continuity, which he deems insufficient to account for personal identity. Both theories require comprehension of what is meant by the term "person-stages", which may be understood as specific instances of a particular person at a particular time, such as, for example, Neville Chamberlain at the time of the British declaration of war against Germany, or you, the reader, at the time of reading this sentence. The theory of memory continuity posits that personal identity consists of first-person memory relations of different person-stages, PN, at different times, TN. By this account, P2 at T2 may be said to be the same person as P1 at T1 if the memory of the former includes that of the latter.
Further, at time T2, P2 need not retain any memory of T0, as long as she retains memory of T1, and P1 retains memory of T0. For example, let us assume that, as a highly frazzled and absent-minded philosophy student, I have lost much of my capacity for memory. In fact, while eating dinner tonight, I do not remember what I ate for breakfast this morning. However, I do remember what I had for lunch today, and at the time that I was eating this lunch I in fact remembered what I had eaten for breakfast. By the theory of memory continuity, then, I have retained my personal identity, at least since breakfast this morning. This type of analysis may be extrapolated backwards in time for as long as my memory has served me, with increments between person-stages as small as necessary, and thus the theory of memory continuity allows me to retain personal identity throughout my life.
Shoemaker invokes the theory of psychological continuity as a response to criticism that personal identity consists of more than simple memory of events. By this objection, propositional memory, practical memory, qualitative memory, and perhaps other forms of memory combine to create the habits, tendencies, and preferences that are just as crucial to my identity as my memory of this morning's breakfast.
Psychological continuity theory simply widens the range of experiences that may be used to explain continuous personal identity, including not only event memory but also all of these additional psychological traits. Yet again, Shoemaker explains the theory in terms of person-stages, such that identity survives if “each member of the series [of person stages] is directly connected, psychologically, to the immediately preceding member”. Thus, psychological continuity theory tells me that I am the sum total of a host of temporally linked experiences.
The value of psychological continuity theory becomes evident when it is compared with other materialist accounts of identity. Roderick Chisolm's insistence that “I am [a physically unchanging] proper part of this gross macroscopic body,” seems counter-intuitive in light of Shoemaker's analysis. Myriad problems associated with Chisolm's view - such as where this entity is located, how it can possibly interact with the brain and yet not experience any physical change, or what happens to it after the death of the body - simply do not arise in Shoemaker's view, because the psychologically grounded account is not based on the continuation of any one physical substance. David Chalmers, on the other hand, comes dangerously close to a dualistic theory of the mind when he posits a metaphysical distinction between mental and physical states.
Psychological continuity theory, in contrast, adheres to a strictly materialistic account of conscious experience. Any supposed gap between mental and physical states is, to the psychological continuity theorist, strictly an epistemological concern. Though we may eventually know every fact about canine hearing abilities, for example, and yet still be unable to experience Stairway to Heaven through a dog's ears, we nonetheless cannot infer that these are not the same. Thus, Shoemaker's exposition of psychological continuity theory avoids the traditional materialist pitfalls suffered by Chisolm's account, and yet does not surrender to a pseudo-dualist point of view like Chalmers'. Its strength as a materialist position is evident.
Despite its clear strengths, though, psychological continuity theory is vulnerable to substantial criticism. Let us examine the case of severe amnesia. Jackie Kennedy, after a terrible plane crash, loses all of her character traits and all of her memory with the one bizarre exception of a recipe for her not-so-famous turkey stuffing. By strict interpretation of the theory of psychological continuity, she would continue to be Jackie Kennedy, despite the fact that anyone who engaged in conversation with her would be unable to discover this, and, having lost all other memory, she would be quite unable to convey her identity to them. It seems rather tenuous to have to pin someone's identity - her entire existence - upon the ability to recall a particular recipe for turkey stuffing!
