 But now suppose that both hemispheres are transplanted, each into a different empty head. (We needn’t pretend that the hemispheres are exactly alike.) The two recipients—call them Lefty and Righty—will each be psychologically continuous with you. The psychological-continuity view as we have stated it implies that any future being who is psychologically continuous with you must be you. It follows that you are Lefty and also that you are Righty. But that cannot be: if you and Lefty are one and you and Righty are one, Lefty and Righty cannot be two. And yet they are: there are indisputably two people after the operation. One thing cannot be numerically identical with two things that are distinct from each other. Suppose Lefty is hungry at a time when Righty isn’t. If you are Lefty, you are hungry at that time. If you are Righty, you aren’t. If you are Lefty and Righty, you are both hungry and not hungry at once: a straight contradiction.