Chisholm’s Peircean argument has considerable intuitive force. It surely seems to many of us that our persistence through time is not simply a matter of convention. No matter what the courts decide, either the person undergoing the painful surgery will be you, or he won’t be you. If this intuition is right, then materialism of the imagined kind is false. For materialism implies that you are an ens per alio, a logical construction. Yet each of us takes himself or herself to be an ens per se.