 David Lewis (in “Counterparts of Persons and their Bodies”, 1971) suggests that the identity of a person with his body (assuming the person and the body, like Goliath and Lumpl, are at all times coincident) is contingent, since bodily interchange is a possibility. He appeals to counterpart theory, modified to allow a variety of counterpart relations, to explain this. Contingent identity then makes sense, since “I and my body might not have been identical” now translates into counterpart theory as “There is a possible world, w, a unique personal counterpart x in w of me and a unique bodily counterpart y in w of my body, such that x and y are not identical”.