In Chapter 36, there is a quick and confusing mention of placing each half of a person’s brain in a different body and then asking which body is the real person. This question, somehow, was to help us understand why the current Chidi is not the same as the Chidi in the reboots. If you did not understand why this is the case, you are not alone. The entire discussion of split-brains is inaccurate and does not support the point Chdi is trying to make.
For those that do not remember, let me back up. In this episode, we find Chidi, in the form of a Janet, trying to explain why the Chidi he is now is not the same Chidi that Eleanor has memories of from all of the reboots. In making his case, he gives the quick standard explanation of John Locke’s account of personal identity. A person is the same person over time if there is continuity of memory. To which, Jason gives the standard student response of, “Just because you don’t remember doing something does not mean you didn’t do it.” This comment then leads Chidi to discussing Derek Parfit and split-brains. You should be thoroughly confused both with Chidi’s explanation of split-brains and why Jason’s good question led to Parfit.
There is no connection between Jason’s question and Parfit. In fact, Parfit’s theory in no way helps Chidi’s position. I cannot explain this other than either the writer did not understand Parfit or the writer was trying to shoehorn in philosophical material where it should not be. What I can explain is Parfit’s split-brain case, what it has to do with personal identity, and why split-brains do not help Chidi’s position.
Parfit, like David Hume, is a bundle theorist. They deny there is personal identity; or as Parfit terms it, the ego theory. According to bundle theory, there is no person; but instead, a series of different mental states unified by a causal relation between them. Split-brains are used as an argument in favor of the bundle theory; however, not in the manner Chidi explains. In the episode, Chidi says if we split a brain in two that has the same memory and put it in two different bodies, then ask which one is the real Chidi? Presumably the idea is that since both brains have the same memory it would be two Chidi’s. This is a fair point and perhaps a point that Parfit or another bundle theorist could make. However, this is not what Parfit is discussing with split-brains.
The brain has two hemispheres connected by neural tissue called the corpus callosum. In some people with a certain type of epilepsy, the only treatment that stops the seizures is to cut the corpus callosum. When this happens, the two hemispheres fail to communicate. In general, people function normally. This is because sensory information is duplicated in each half of the brain. However, what happens when it is not?
Suppose you put a headset on a person and showed one eye blue and another eye red. You put a pencil in each hand. Then you ask the person to write down what color is seen. One hand will write blue and the other hand red. Now, the person is asked to write down how many colors are seen. The person will write one. However, it seems clear that the person is seeing two, so how can the person honestly believe she is only seeing one color?
The answer is that the person now has two streams of consciousness where there was once one. Each hemisphere now only has its own experience. Given that, how many people are in the same body? Is it just one or is it now two? Most of the memories are with both sides, so maybe there is only one person. However, the memories differ, so maybe it is two people in one body. Yet, the person will still think it is just one person in one body.
It is because of these issues that Parfit thinks we need to reject the ego theory. Instead, if we stick to reducing everything to simply a description of processes there is no problem. Where once there was one stream of consciousness from a unified brain there are now two. That is all that needs to be said. This is because in reality, there never was a person to begin with. It has always just been a series of mental states in a brain. That has not changed. It is the ego theory that leads to problems with split-brains. This is a strong reason to reject the ego theory in favor of the bundle theory.
In case it is not clear, such a view does not help Chidi. Chidi wants to maintain that it was not him in those reboots, but rather a different Chidi. Therefore, it was some other Chidi that was in love with Eleanor, not the current or “real” Chidi. However, such a view supports personal identity. If all that exists is a series of processes, then there was never a Chidi to begin with.
