Each cerebral hemisphere in Patient O.S., a callosum-sectioned patient, appears to possess mental properties deserving of conscious status. The observations seem to answer many questions concerning the issue of whether the mechanisms of consciousness can be split and doubled by split-brain surgery. As P.S. is the first split-brain patient clearly to possess double conscious processes as well as the first with extensive bilateral linguistic skills, the observations suggest that the special nature of human conscious experience is closely tied to linguistic processes.