The Organism View Defended

McMahan cites the case of the conjoined twins, Abigail and Brittany Hensel, each having 'her own private mental life and her own character, each [feeling] sensations only on her own side of the body, and each [having] exclusive control over the limbs on her side. It has been found in experiments on hemispheric commissurotomy that when different sensory stimuli are presented to each of the hemispheres, one hemisphere could be unaware of what was presented to the other hemisphere.6 The upshot of such studies is that they seem to suggest that one's consciousness could be divided.7 On this basis, McMahan hypothesizes that if a commissurotomy was performed at birth and each hemisphere was then for many years presented with different stimuli, while the other was anaesthetized, such a procedure could produce two different minds, each with a different set of experiences, dispositions, beliefs, and memories.8 McMahan argues that if this happens, then there would be two people coexisting, but there would only be one organism.