I argue that if minds supervene on the intrinsic physical properties of things like brains, then typical human brains host many minds at once. Support comes from science-nonfiction realities that, unlike split-brain cases, have received little direct attention from philosophers. One of these realities is that some patients are functioning (albeit impaired) and phenomenally conscious by all medical and commonsense accounts despite the fact that they have undergone a hemispherectomy: an entire brain hemisphere has been fully detached. Another is the (...) Wada test, in which a patient has each hemisphere anesthetized, one after the other, while the other hemisphere is awake and functioning—again, phenomenally conscious by any standard. I will argue that hemispherectomies, Wada tests, and related procedures each present cases in which the minds that exist after the detachment (or anesthetization) of a hemisphere are surviving minds which must be associated with the surviving (or un-anesthetized) hemisphere. I will argue that such surviving minds existed before the medical procedure, instantiated by the then-intact hemisphere that was due to survive the loss of its complementary hemisphere. If so, then the typical subject has at least three minds: a “left hemisphere mind”, a “right hemisphere mind”, and a “whole brain mind”. But the argument generalizes to cases in which smaller portions of the brain are lost, yielding a great number of additional minds, some overlapping. Some important ethical implications are raised and briefly examined. (shrink)

One might expect functionalism to imply that personal identity is preserved through various operations on the brain, including transplantation. I argue that this is not clearly so even where the whole brain is transplanted. It is definitely not so in cases where only the cerebrum is transplanted, a conceivable kind of hemispherectomy, and even certain cases in which the brain is "gradually" replaced by an inorganic substitute. These results distinguish functionalism from other accounts taking what Eric T. Olson calls the (...) "Psychological Approach" to personal identity, enabling it to avoid some of his objections to them. (shrink)

In "Consciousness Explained," Dennett (1991) denies that split-brain humans have double consciousness: he describes the experiments as "anecdotal." In attempting to replace the Cartesian Theatre of the Mind" with his own "Multiple Drafts" view of consciousness, Dennett rejects the notion of the mind as a countable thing in favour of its being a mere "abstraction." His criticisms of the standard interpretation of the split-brain data are analyzed here and each is found to be open to objections. There exist people who (...) have survived left ["dominant"] cerebral hemispherectomy; by Dennett's criteria, they would not have minds. (shrink)

Half a Brain is Enough is the extraordinary story of Nico, a three-year-old boy who was given a right hemispherectomy to control his severe intractable epilepsy...

When circumscribed brain regions are damaged in humans, highly specific iimpairments in language, memory, problem solving, and cognition are observed. Neurosurgery such as "split brain " or hemispherectomy, for example has shown that encompassing regions, the left and right cerebral hemispheres each control human behavior in unique ways. Observations stretching over 100 years of patients with unilateral focal brain damage have revealed, withouth the theoretical benefits of "cognitive neuroscience" or "cognitive psychology," that human behavior is indeed controlled by the brain (...) and its neurons. (shrink)

In the Arthur Stanley Eddington Memorial Lecture for 1965 Eccles uses his considerable knowledge to argue that neurophysiology can give clues to the physical requirements of the unity of conscious experience, but it cannot fully account for it. The way is thus left open to postulate or believe in the special creation of the soul as the principle of self-identity. Specifically, Eccles argues that self-identity is not reducible to gene identity. He does not, however, go into the problems surrounding the (...) origin of the employment of the notion of self-identity; and in this respect his analysis is uncritical from a philosophical point of view. Interestingly enough, some of the positive bits of neurophysiological theory that Eccles puts forth in this short lecture, in particular, the theory of hemispheric localization of the higher functions, have been shaken considerably in the past few months by the results of the Coe hemispherectomy.—E. A. R. (shrink)