Thomas Nagel, in “Brain Bisection and the Unity of Consciousness,” presents a thesis in favor of the nonexistence of selves in human beings. Selves, in the case of Nagel's argument, are the physiological bases of the mind that constitute the subject of experience. A self can be thought of as the fundamental person, or “personal identity”. There has been substantial difficulty in identifying the number of people present in a human being, and the initial and apparently apparent answer of “one” becomes less convincing upon examination of further evidence. (Nagel, 1971, p. 396) In particular, medical patients who have undergone partial or complete body callosotomy exhibit strange behavior under specific conditions that cast doubt on the conclusion that every human being has a self. The corpus callosum, the cerebral commissure between the two hemispheres of the brain, serves as a communication route for messages between the hemispheres. Typically, information from the sensory organs is duplicated or communicated throughout the brain regardless of the origin of the sensation and the hemisphere to which it is directly connected via the corpus callosum. (Nagel, 1971, pp. 396-400; Sperry, 1968, pp. 723-725; Sperry, 1984, pp. 661-663) When the corpus callosum is severed, it is often a surgical procedure of last resort to resolve certain medical problems as with epilepsy, not all information can be transmitted between the disconnected hemispheres, and the resulting effects provide interesting evidence that has given rise to many theories regarding selves and their accounting. These effects have been demonstrated in monkeys, humans and cats through carefully designed studies and experiments. For human patients, a special apparatus is used to stimulate each hemisphere separately....... middle of paper ...... sphere dominance to understand the intentions of others: Evidence from a split-brain patient. BMJ case reports [doi:10.1136/bcr.07.2008.0593].Puccetti, R. (1973), “Brain Bisection and Personal Identity”, British Journal for thePhilosophy of Science 24, 339-55.Puccetti, R. (1989 ). Two brains, two minds? Wigan's theory of mental duality. The British Journal for the Philosophy of Science, 40:137-144. Sperry, R. (1968). Hemispheric disconnection and unity in conscious awareness. American Psychologist, 23, 723-733. Sperry, R. (1984). Consciousness, personal identity and the split brain. Neuropsychology. 22, 661-673.Vining, E., Freeman, J., Pillas, D., Uematsu, S., Carson, B., Brandt, J., Boatman, D., Pulsifier, M., Zuckerberg, A. (1997). Why would you remove half your brain? The outcome of 58 children after hemispherectomy. Pediatrics, 100, pp. 163-171.