The First-Person Pronoun (2): Split Brains

Abstract This chapter examines the philosophical and psychological implications of split-brain cases for the use of the first-person pronoun. It begins by contrasting commonsense assumptions about personal identity with the abnormal situation of patients whose hemispheres act independently, raising the dilemma of whether such individuals contain one subject, two, or a composite of three. Through R. W. Sperry’s experiments, Thomas Nagel’s challenge, and subsequent analyses, the chapter argues that while hemispheres exhibit I-thoughts, they are “I-blind” because their utterances of “I” refer only to the whole patient rather than to themselves. The chapter critiques alternative views of ambiguity and explores extensions through Parfit’s thought experiment, Korsgaard’s analogy, and further cases such as Sphero, Subo, and Pairstein, highlighting distinctions between reversible and irreversible forms of I-blindness as well as the conditions of first-personal unity. Finally, it concludes that the irreducible capacity for self-reference underlies personal identity, but in split-brain and related scenarios, spheres and sub-units lack this capacity, thereby illuminating the limits of agency, rationality, and unity in abnormal or hypothetical cases.