 Third, counterpart theory might offer an answer to puzzles involving possible fission or time-travel. These might be analysed as scenarios in which an individual has multiple counterparts relative to the same counterpart relation. Lewis intuits that he “might have been twins” (Lewis 1973, 40–1), because the fetus from which he developed might have undergone fission. (See also Schwarz 2014, Karmo 1983.)