Commissurotomy surgery has lately attracted considerable philosophical attention. It has seemed to some that the surgical scalpel that bisects the brain bisects consciousness and the mind as well; and that the ordinary concept of a person is thereby most seriously threatened. I shall assess the extent of the threat, arguing that it is overestimated. The argument begins with section III; section II, which describes the operation and its effects, should be omitted by those already familiar with these facts.

Commissurotomy surgery has lately attracted considerable philosophical attention. It has seemed to some that the surgical scalpel that bisects the brain bisects consciousness and the mind as well; and that the ordinary concept of a person is thereby most seriously threatened. I shall assess the extent of the threat, arguing that it is overestimated. The argument begins with section III; section II, which describes the operation and its effects, should be omitted by those already familiar with these facts.

Many have claimed that split-brain patients are actually two persons. I maintain that both the traditional separation argument and the more recent sophistication argument for the two persons interpretation are inadequate on conceptual grounds. An autonomy argument is inadequate on empirical grounds. Overall, theoretical and practical consequences weigh heavily in favor of adopting a one person interpretation.

To the extent that indeterminacy intervenes between our reasons for action and our decisions, intentions and actions, our freedom seems to be reduced, not enhanced. Free will becomes nothing more than the power to choose irrationally. In recognition of this problem, some recent libertarians have suggested that free will is paradigmatically manifested only in actions for which we have reasons for both or all the alternatives. In these circumstances, however we choose, we choose rationally. Against this kind of account, most (...) fully developed by Robert Kane, critics have pressed the demand for contrastive explanations. Kane has responded by arguing that the demand does not need to be met: responsibility for an action does not require that there be a contrastive explanation of that action. However, this response proves too much: it implies that agents are responsible not only for the actions they choose, but also for the counterfactual actions which were equally available to them. (shrink)

In this paper it is argued that the experimental data on commissurotomy patients provide no grounds for denying the singular personhood of commissurotomy patients. This is because, contrary to most philosophical accounts, there is no “unity of consciousness” discriminating condition for singular personhood that is violated in the case of commissurotomy patients, and because no contradictions arise when singular personhood is ascribed to commissurotomy patients.

In this paper it is argued that the experimental data on commissurotomy patients provide no grounds for denying the singular personhood of commissurotomy patients. This is because, contrary to most philosophical accounts, there is no “unity of consciousness” discriminating condition for singular personhood that is violated in the case of commissurotomy patients, and because no contradictions arise when singular personhood is ascribed to commissurotomy patients.

Biological foundations of the psychoneural identity hypothesis are explicated and their implications discussed. "Consciousness per se" and phenomenal contents of consciousness per se are seen to be identical with events in the (unobserved) brain in accordance with Leibniz's Law, but only informationally equivalent to neural events as observed. Phenomenal content potentially is recoverable by empirical means from observed neural events, but the converse is not possible. Consciousness per se is identical with events which do not represent anything distal to sensory (...) receptor-transducer systems. Thus, on the psychoneural identity hypothesis, consciousness per se comprises directly physical events-in-themselves rather than being a Euclidean representation of physical events as is the case for phenomenal content. After comparing consciousness per se to "onta," a paradox is suggested: rather than being irreducible to physical reality, consciousness per se is the only experience congruent with the ultimate nature of physical reality as conceived by contemporary physics. (shrink)