“Conscious experience is at once the most familiar thing in the world and the most mysterious. There is nothing we know about more directly than consciousness, but it is far from clear how to reconcile it with everything else we know.”
– David J. Chalmers
WE ARE ALL intimately familiar with that voice in our heads, nagging as we reach for a second helping of chocolate eggs in the wake of Easter, and judging as we have to settle for a looser belt hole a week later. We are all also accustomed to the different masks we wear in various social situations. I would be ruthlessly mocked could my close friends see the way I behave around my girlfriend, snuggled on the couch on a Sunday night, and my parents would be hard pressed to recognize me. But this apparent discontinuity is a perfectly normal aspect of human existence – psychologists have long known that situation exerts a significant influence on personality – and I have never experienced anything which would seem to indicate that there was more than one self calling the inside of my skull home. As a matter of conscious experience, I am just as much me whilst goofing around with my girlfriend as I am typing this essay and sipping green tea. But am I really? As a result of a fascinating avenue of inquiry involving patients who have had the hemispheres of their brain surgically separated, psychologists, cognitive scientists, and philosophers have begun to argue that there is every reason to believe in the divisibility of consciousness – the existence of a separate centre of consciousness in each of the divided hemispheres – and you and I might not be as different to these patients as we think.