 For another, it allows us a kind of inconstancy in our modal predications. Could Malloy have been brought by a stork, or must he have had the parents he actually had? In some moods we think one, in other moods we think another. Lewis thinks that counterpart theory can reflect our indecision. There is a world with someone brought by a stork who has a life much like Malloy’s. Is he one of Malloy’s counterparts? Well, he is according to some counterpart relations, and not according to others. When one of the former relations is contextually salient, it’s true to say that Malloy could have been brought by a stork. When more demanding counterpart relations are salient, he isn’t one of Malloy’s counterparts, and indeed all of Malloy’s counterparts share his parents. (More precisely, all of his counterparts have parents who are counterparts of Malloy’s actual parents.) In those contexts, it is true to say that one’s parentage is essential. Throughout his career, Lewis uses this inconstancy of the counterpart relation to resolve all manner of metaphysical puzzles, from puzzles about personal identity (1971c) to puzzles about truthmakers (2003b). The final section of Plurality is Lewis’s most extended argument that this variability of the counterpart relation is a strength, not a weakness, of the theory.