Abstract

Important conceptual and metaphysical issues arise when we try to understand the mental lives of “split-brain” subjects. How many distinct streams of consciousness do they have? According to Elizabeth Schechter’s partial unity model, the answer is one. A related question is whether co-consciouness, in general, is transitive. That is, if α and β are co-conscious experiences, and β and γ are co-conscious experiences, must α and γ be co-conscious? According to Schechter, the answer is no. The partial unity model faces some serious objections. Its underpinnings are suspect, and ways of working out the model fall into trouble of various sorts: incoherence, emptiness, or unacceptable indeterminacy about the identity of (token) conscious states. One apparent lesson is that a subject can host two distinct conscious experiences of the same sort. Another is that the co-consciousness relation is transitive after all.