The central concepts concerning consciousness that I shall try to defend have already been presented in some detail (Sperry, 1952, 1964, 1965). Accordingly, I shall review them only in brief outline, devoting the bulk of the discussion to various peripheral aspects and implications that previously have had less emphasis. At the outset let me make it clear that when I refer to consciousness I mean that kind of experience that is lost when one faints or sinks into a coma. It is the subjective experience that is lacking during dreamless sleep, that may be obliterated by a blow on the head, by anoxia, or by pressure on the inner walls of the third ventricle during brain surgery. On the positive side we can include as conscious events the various sensations elicitable by a local electric current applied to the unanesthetized brain, or the pain of a phantom amputated limb, as well as most of our waking subjective experience, including self-consciousness.