Who am I? What makes me, me? The theory of personal identity has been considered one of the most complicated questions that philosophy has taken a deeper look into. The theory of personal identity tries to “deal with the questions about how an individual at one time and place is the same individual at another time and place”. When we look at personal identity, we are trying to figure out what sets us apart from other pieces of matter, species and individuals. In this essay I will discuss John Locke’s criterion of sameness of consciousness for the theory of personal identity and why he does not think that other physical or psychological criteria fit, a challenge to Locke’s criterion posed by Thomas Reid using the logic of transitivity analogy, and lastly how the suggested idea of overlapping chains of memory that Derek Parfit poses to reform Locke’s view so that it may meet the challenge posed by Thomas Reid is a good solution to the challenge because it keeps Locke’s theory intact and also adds the transitivity property that Reid challenges Locke’s theory on.
When discussing personal identity, the criterion of identity will strongly depend on the object that you are talking about. There have been many viewpoints as to what the criterion of personal identity of the self or a person is. Some viewpoints suggest that the criterion for the self is organic; that our body is what identifies us over time. Locke states that this criterion is not applicable for personal identity of a person because of situations like body switch (Freaky Friday situation). If the consciousness of two people were to switch, everyone would think that you are the same person because you look like the same person. However, it is not actually you in your body and because there is a different consciousness in your body, and your body is no longer you; your body cannot define your personal identity. Other views describe the criterion as being substance that makes us the same over time. Substance includes both non-physical (soul) and physical substances. According to Locke, substance as a criterion is not applicable for personal identity of a person because of situations like death. When you die, you may be made of the same substance, but if you cease to think (thinking is connected to being a person) then you cease to exist and have no personal identity.
Locke looks towards a psychological criterion to define personal identity of a person. According to Locke, a person or the self is different than just matter and just a living thing. A person is “a thinking intelligent being that has reason and reflection and can consider itself as itself, the same thinking thing in different times and places; which it does only by that consciousness which is inseparable from thinking”. This describes what is known as sameness of consciousness. We are the same person to the point where we are conscious of our past and future memory or mental state in the same way that we are conscious of our current memory or mental state. This criterion can also be broken down into an analogy said by Locke: person x is the same as person y if person y is consciously connected to x in the sense that person y can remember the thoughts and actions of person x. According to Locke, the necessary criterion of personal identity is sameness of consciousness. This sameness of consciousness comes directly from memory and experience. Locke believes that the sameness of consciousness is the ideal criterion of personal identity for a person because since consciousness is always connected to thinking, and being able to think is what makes a person a person and allows that person to distinguish its own thoughts from another’s, as far back as our consciousness can be extended to any past thought, so far back will our identity extend. As far back as the person can repeat or reflect on a past thought or action with its current consciousness, so far back is the personal identity of the person.
Thomas Reid, as well as many other philosophers and critics who oppose the idea of sameness of consciousness criterion, otherwise known as memory theory, have a very hard time agreeing that sameness of consciousness is a necessary criterion for personal identity. They understand that the sufficient condition that the view of sameness of consciousness criterion is trying to state is achievable; if I remember eating a triple chocolate fudge bar, then I must have been the one that really ate the triple chocolate fudge bar. However, they don’t understand how sameness of consciousness is a necessary condition for personal identity; that if I cannot remember eating the triple chocolate fudge bar, then it is impossible that I was the one who ate the triple chocolate fudge bar. The fact that it is impossible for you to have the same personal identity if you cannot remember that past thought or action is where Reid’s challenge arises.
Reid’s challenge towards Locke’s theory is presented in the form of the logic of transitivity analogy that states that if x is related to y, and y is related to z, then x is related to z. Using a modern example, Reid’s theory follows that the little girl who played in the sand(x) is the same person who was a student at the University of Toronto(y) and the person who was a student at the University of Toronto(y) is the same as the woman who is CEO of a banking firm(z), and therefore using the logic of transitivity, the little girl who played in the sand(x) is therefore the same person as the woman who is CEO of a banking firm(z). Reid successfully shows that transitivity allows the little girl who played in the sand and the woman who is CEO of a banking firm to have the same personal identity despite the fact that the woman who is CEO of a banking firm may not remember ever being the little girl who played in the sand. Due to the fact that Reid’s challenge is successful in showing that the CEO and the little girl who played in the sand can be the same person and share the same personal identity, it shows that Locke’s theory denies the fact that the CEO and the little girl who played in the sand are the same person which ignores the logic of transitivity and is therefore false. Locke’s criterion does not take into consideration the transitivity property and Reid’s challenge points out this clear and big flaw.
Reid’s challenge explains that Locke’s criterion of personal identity completely ignores the logic of transitivity. His challenge proves that Locke’s criterion, without any changes applied, fails because it cannot just ignore the transivity property. However, Derek Parfit, a British philosopher who also explored the topic of personal identity, suggested a possible solution to slightly change Locke’s criterion to make it so that it meets this challenge. Parfit’s suggested solution is to make the criterion of personal identity overlapping chains of memory. Going back to the modern example of the little girl who played in the sand and the CEO, Parfit’s suggested solution would state that if the student at the University of Toronto could remember being the little girl who played in the sand, and the CEO remembered being the student at the University of Toronto, then this overlapping chain of memories would allow the CEO to be the same person as the little girl who played in the sand.
This solution helps Locke’s theory overcome Reid’s challenge while still defending the core parts of Locke’s theory. Parfit’s overlapping memory theory allows for the CEO and the little girl to be the same person, which covers the transitivity property. It allows x to be the same person as z. It also still allows for sameness of consciousness or memory theory to be the necessary criterion of personal identity. It fulfills the sufficient condition of the criterion: if I remember eating a triple chocolate fudge bar, then I must have been the one that really ate the triple chocolate fudge bar, and fulfills the necessary condition of the criterion: If I don’t remember eating a triple chocolate fudge bar, as long as I remember buying the chocolate fudge bar to eat than I am the same person who later ate the triple fudge chocolate bar because I have overlapping chains of memory that allow me to be the same person. The necessary condition is fulfilled because it shows that through the overlapping chains of memory I may not remember everything but as long as I remember enough to continue the chain of memories, I will be the same person.
Although this solution is a sound response to Reid’s challenge, it does not give a specific conclusion for what the criterion of identity truly is. It states that instead of the criterion being one specific definition, it is more like a group of experience, memories and thoughts that make us the same person at time one and time two. However, Parfit’s argument is a sound response to Reid’s challenge and therefore does successfully transform Locke’s view so that it will meet the transitivity property as well as the necessary condition of consciousness. Overall, Locke’s view on personal identity is just one of many and there will be many more to come on this complicated and deep topic.