Most of us have a sense of who we are. Yet identity is a tricky business. If, for example, a person’s memories could be erased and substituted with another person’s memories, would he or she still be the same person? These are the types of metaphysical questions that have philosophers looking at their feet. Pondering what constitutes identity has its practical applications too. In order to be accused of identity fraud, or determine whether an infant is a person, requires constructing a picture of identity that we can view these questions through.
There are many competing theories of identity. One theory is the body theory of identity. If, for example, a body has been violated, then the violator has disrespected the identity of the person. This reasoning has its merits but quickly falls apart upon further reflection. For example, the cells that make up a body are continuously destroyed and renewed. The body is not a fixed object but continuously changes with the flow of time. Therefore, according to this reasoning, a person cannot have a fixed identity because the body is constantly changing.
Another theory of identity is the brain theory. Rather than being a body, an identity is found in a person’s brain. This solves many practical medical dilemmas. Alzheimer’s, for example, seems to gradually deteriorate a person’s identity due to its effects on the brain. In other cases, a person’s identity “splits” into two different stream of consciousness that exhibit control over the body at different times. This is known as multiple personality disorder.
Yet this picture of identity is not without its own short comings. If, for example, an evil surgeon could gradually pick a way a patient’s neurons while simultaneously substituting them with silicon neurons, the artificial brain at the end of the procedure would not be the same as the organic brain at the beginning of the procedure. At what point during the surgery is the person’s identity lost?
In an effort to salvage the brain identity hypothesis, some philosophers have proposed that it is not the organic tissue that makes up the brain that matters in regards to identity, but the information stored in the material. This is known as the psychological view of identity. In particular, what connects an adult to their childhood self is the psychological chain between them.
Yet the psychological view of identity is not without its own shortcomings. For example, suppose a person were transferred from Earth to Mars via teleportation machine instantaneously. Upon stepping into the teleportation machine, the person’s entire body is destroyed. The information is preserved and instantaneously transferred to a copy on Mars. Does the person survive the transfer? According to the psychological continuity view the person does survive the transfer because the psychological continuity was preserved.
Here is where the thought experiment pulls a fast one. Suppose that a malfunction occurs upon entering the teleportation machine. The machine makes an exact copy of the original person but fails to annihilate the original. Our intuitions suggest that the identity of the original person is preserved on Earth and a copy of the person is on Mars. According the psychological continuity view, however, neither person is the original! In particular, the moment the teleportation machine malfunctions, the psychological continuity of the original person splits into two separate streams, thus annihilating the original stream of consciousness.
The highlighted theories of identity all contain their fair share of strengths and weaknesses. Some philosophers have even gone so far to argue that identity is an illusion. Philosophers of language argue that identity is not a description but a reference used to point to a particular object in every possible world state. Using identity has a reference point rather than a description seems to be on the right track, however, mysteries still remain.
By Nathan Cranford