 And Lewis used counterpart theory throughout his career to resolve metaphysical puzzles in fields stretching from  personal identity  (“Counterparts of Persons and Their Bodies” (1971c)) to  truthmaker theory  (“Things qua Truthmakers” (2003b)). Indeed, Lewis’s original statement of counterpart theory is in one of his first published metaphysics papers (“Counterpart Theory and Quantified Modal Logic” (1968)).