Could a single human being ever have multiple conscious minds? Some human beings do. The corpus callosum is a large pathway connecting the two hemispheres of the brain. In the second half of the twentieth century a number of people had this pathway cut through as a treatment for epilepsy. They became colloquially known as split-brain subjects. After the two hemispheres of the brain are cortically separated in this way, they begin to operate unusually independently of each other in the realm of thought, action, and conscious experience, almost as if each hemisphere now had a mind of its own.
Philosophical discussion of the split-brain cases has overwhelmingly focused on questions of psychological identity in split-brain subjects, questions like: How many subjects of experience is a split-brain subject? How many intentional agents? How many persons? On the one hand, under experimental conditions, split-brain subjects often act in ways difficult to understand except in terms of each of them having two distinct streams or centers of consciousness. Split-brain subjects thus evoke the duality intuition: that a single split-brain human being is somehow composed of two thinking, experiencing, and acting things. On the other hand, a split-brain subject nonetheless seems like one of us, at the end of the day, rather than like two people sharing one body. In other words, split-brain subjects also evoke the unity intuition: that a split-brain subject is one person.
Elizabeth Schechter argues that there are in fact two minds, subjects of experience, and intentional agents inside each split-brain human being: right and left. On the other hand, each split-brain subject is nonetheless one of us. The key to reconciling these two claims is to understand the ways in which each of us is transformed by self-consciousness.
Industry Reviews
Schechter has written an exceptionally good book. Its particular virtues are the care and rigor with which arguments are developed. . . . Schechter makes use of a considerable amount of neurobiological detail, not all of which is made accessible to the non-expert -- this is as much a cognitive science book as a philosophy book . . . Schechter's writing is very appealing -- deft and stylish, in an understated way. This may help keep you going as you make your way through a lot of argument. The book seems to me an exemplary piece of naturalistic philosophy of mind . . . a detailed, careful attempt to get to the bottom of the way the human split-brain phenomenon actually is. The result is a very valuable book indeed. * Peter Godfrey-Smith, Notre Dame Philosophical Reviews *
Moving seamlessly between philosophy, psychology and neuroscience, Self-Consciousness and 'Split' Brains is a rich and wonderfully stimulating account of the commissurotomy syndrome. This is required reading for anyone who wishes to understand the self and the ties that unify consciousness, embodiment, and agency. * Tim Bayne, author of The Unity of Consciousness *
Schechter's book illustrates the best kind of philosophy of mind: careful philosophical analysis coupled to penetrating engagement with empirical work. Her discussion of the split-brain phenomenon illuminates the individuation of minds, the unity of consciousness, and the nature of agents and persons. The book will richly reward careful reading. * Wayne Wu, Center for the Neural Basis of Cognition, Carnegie Mellon University *
Split brains have puzzled psychologists and neuroscientists since the first operations. Schechter has mastered the massive literature and argued for profound lessons for the philosophy of mind and action. Inquiring minds will be enthralled. * Walter Sinnott-Armstrong, Department of Philosophy and the Kenan Institute for Ethics, Duke University *
