About Identity and Diversity

In John Locke’s “Of Identity and Diversity,” Locke makes the following claim: person X at time t2 is identical to person Y at time t1 if and only if person X at time t2 remembers what person Y at time t1 saw and did. In this paper, I will explain this claim and show how Locke uses it to develop his theory of personal identity. Then, I will show that Locke’s theory does not work because of 1) its failure to preserve the transitivity of identity and 2) its circularity. Finally, I will rework Locke’s claim so as to address these objections by including the notion of psychological continuity as a way to define identity.

I will start by explaining Locke’s claim. He claims that “for as far as any intelligent being CAN repeat the idea of any past action with the same consciousness it had of it at first, and with the same consciousness it has of any present action; so far it is the same personal self” (10). This claim can be simplified as follows: person X at time t2 is identical to person Y at time t1 if and only if person X at time t2 remembers what person Y at time t1 saw and did. This means that for someone to be identical to the person that they were at some time in the past, it is both necessary and sufficient for them to remember and have a memory connection to what their past self saw and did at that given time in the past. For example, if 23 year old Linda gets into a car crash and loses her memory as a result, then, according to Locke, she is no longer identical to who she was before the car crash. The ability to connect memories is an essential aspect of consciousness and is necessary for personal identity.

I will now explain how Locke uses the aforementioned claim to develop his theory of personal identity. Locke says that a person is a thinking thing that has consciousness and, as a result, possesses the ability to recognize itself as a thinking thing even at different times or places. This ability to think of oneself as a self is what constitutes personal identity. One’s

personal identity reaches as far as consciousness can extend backwards into one’s past. The sameness of memory is both necessary and sufficient for the sameness of identity. Your consciousness must be extended overtime and you must have memories of your past actions and experiences in order for your identity to be considered the same. In other words, you must be conscious of past experiences (memories) as much as you are conscious of present experiences.

The first problem with Locke’s theory of personal identity that I will examine is its failure to preserve the transitivity of identity. In the paragraph that follows, I will use my own variation of Thomas Reid’s “brave officer” paradox to show how Locke’s theory contradicts itself. Suppose a now retired lawyer remembers failing an exam in law school. At the time that she failed the exam, she remembers getting food poisoning in 8th grade. However, as a retired lawyer, she no longer remembers getting food poisoning in 8th grade. According to Locke’s theory of identity, the retired lawyer, A, is the same person as the law school student who failed an exam, B, who is the same person as the 8th grader who got food poisoning, C. However, the retired lawyer is not the same person as the 8th grader. The retired lawyer remembers what the law school student saw and did, and has a direct memory connection with the law school student, so they are identical persons. The retired lawyer does not, however, remember what the 8th grader saw and did, so they are not the same person. But how can it be that A=B and B=C, but A?C? This objection identifies a contradiction in Locke’s theory of identity: person A must be the same as person C, but person A can not be the same as person C. It suggests that either identity is not transitive, or Locke’s theory of identity is wrong. Therefore Locke must be wrong. Identity is transitive, but memory is not, so memory can not constitute identity like Locke suggests.

I will now explain a second objection which deals with the circularity of Locke’s theory of identity. Locke defines identity in terms of memory, and then defines memory in terms of identity. He says that in order for person X at time t2 to be identical to person Y at time t1, person X must remember what person Y saw and did. What Locke fails to recognize in his argument is that memory presupposes identity, therefore identity can not be constituted by memory. To remember failing an exam, you must remember yourself failing. For a present mental state (memory) to represent a past mental state seems to rely on both mental states belonging to the same person. But to be the same person you were at some time in the past you must have a present mental state (memory) of that past mental state. This is how Locke’s theory is circular.

Locke’s central idea can be reworked to save his theory from these objections. Instead of reducing identity to one thing like memory, we can account for personal identity through a combination of quasi-memory and psychological continuity.

A person quasi-remembers an experience if 1) the person remembers having the experience, 2) someone really did have the experience at that time, and 3) the causal connection between someone having the experience and that person remembering having the experience is the same as it is in genuine memory. This solves the circularity problem in Locke’s theory of identity because quasi-memory does not presuppose identity. The person experiencing the event does not have to be identical to the person remembering the event.

Psychological continuity allows identity to be defined not by strict memory connections, but by memory chains. This modified account of Locke’s theory of personal identity does not face the problem of transitivity. The retired lawyer can be psychologically continuous with the 8th grader, despite not being able to remember getting food poisoning. This is because the retired lawyer remembers the experiences of the person who failed an exam in law school, and that person remembers the experiences of the person who got food poisoning in 8th grade. This forms a memory chain through which things like personality traits, habits, beliefs, desires, etc. can all connect. It is now possible for A=B, B=C, and A=C, without A directly remembering the experiences of C. A direct memory connection is not required for identity, but rather an overlap of psychological connections.

Locke develops his theory of identity through the claim that memory constitutes identity. I have used the transitivity objection and circularity objection to show why his theory is insufficient as is. I have also proposed the notion of psychological continuity along with quasi-memory to save Locke’s theory against these objections.

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