Phenomenal Self and Divided Brain

Abstract

Famous experiments on patients who underwent commissurotomy, such as those conducted by Roger Sperry, perplex philosophers. These patients, whom we consider single persons, seem to have two separate streams of consciousness due to a severed corpus callosum. Consequently, the patient appears to be a single biological organism inhabited by two distinct psychological beings. This paper aims to explore the causes of our uncertainty about the singularity of the commissurotomy patient. The starting point is Thomas Nagel’s description of what the paper refers to as the phenomenal self. It is argued that to imagine the self without any experience is inherently impossible. Additionally, an analysis of Derek Parfit’s physics exam thought experiment reveals that it is also impossible to simultaneously conceive of two separate streams of consciousness. Therefore, the reason we struggle to view the patient as a single person must stem from an assumption about the relationship between the self and the unity of consciousness. An analysis of Tim Bayne’s account suggests that this assumption frames the self as an entity that provides the unity of consciousness. The proposed revision inverts this relation: the unity of consciousness is a foundation that sustains the phenomenal self. This thesis leads to an epiphenomenalist view of the self. The result is used to interpret the commissurotomy patient as a single person. This interpretation is compared with Tim Bayne’s “switch model” of the case.