Am I Only One Person?

Personal identity has been one of the most commonly debated topics in the history of philosophical thought, the question of what it is that makes the `me` who existed when I was born and the `me` who exists now the same `me`. There have been numerous theories of identity formulated by the greatest intellects, all attempting to answer this crucial question. However all of these theories rely upon a basic assumption that was brought into a question by a series of experiments performed in the late 1950s by Myers and Sperry, experiments that are considered far too rarely when the question of personal identity is raised. The assumption is that of the unity of personhood, the intuition that each human mind is singular and indivisible. These experiments were performed upon people who had undergone what is known as a `split-brain` operation. The operation was originally put into use as a treatment for severe epilepsy, and essentially involves the severing of the higher connections between the left and right cerebral hemispheres of the brain. In everyday life, recipients of the treatment seemed to act completely normally, suggesting no unexpected side effects of the severing of communication between the two hemispheres, despite the fact that each hemisphere has specific tasks that it performs. However under certain experimental conditions, these people display extraordinary behaviour. The two brain hemispheres can be treated separately by partitioning the subject`s visual field, because a different half of the brain deals with the input from each eye. It is simpler to explain the rest with a hypothetical example, though it is equivalent to the real experiments: the subject`s right field of vision is shown a red stimulus, and the left field is shown a blue stimulus. When asked to say which colour was being seen the subject would reply by saying red, the left hand side of the brain being responsible for speech. The subject would also deny any experience of blue. However if asked to write which colour was being seen the subject would write the word blue. The right hand side of the brain is responsible for motor functions such as writing. There have been much stranger real examples, such as a man whose left hand repeatedly pushed his wife away whilst the other tried to hold it back. Essentially two different experiences are being had simultaneously, and the experience is completely separated by the split-brain. Two intuitive principles when considering the mind are ownership, the idea that every conscious experience must be an experience of someone, and awareness, the idea that if someone has a conscious experience then it must at least in principle be possible for him or her to be aware of that experience. With ownership, each of these two separate experiences must have an owner, and with awareness, it is clear that the subject is not connected to one of the experiences. This means that there are two separate minds at work here. One could respond by saying that this division of mind is simply a quirk of an odd experiment and strangely applied experimental conditions, with no bearing upon our usual conception of mind, and therefore no implications upon the way in which we think about personal identity. Either the second mind is created by the original surgery, or by the conditions in these specific cases. However such an opposition holds little weight. It seems absurd that merely by performing or reversing surgery, or by turning on blue or red stimuli that an entirely new person could be created and then destroyed. It is simply ad hoc speculation. Therefore what is clear is that the conventional conception of the unity of the single human mind has been brought into serious doubt, and that any theory of what makes `me` persist over time must attend to the fact that this singular `me` does not seem so certain anymore.