Lewis's counterparts theory

Lewis's counterparts theory addresses how we identify the same person across different possible worlds (alternative scenarios). Instead of assuming there is one fixed individual everywhere, the theory suggests that a person in one world has various "counterparts" in other worlds—similar but not identical individuals. These counterparts share essential qualities and relationships, allowing us to say that a person in one world is the same as their counterpart in another, based on similarity. This approach helps clarify debates about identity and change by focusing on how individuals relate across different circumstances rather than assuming absolute sameness across all possible worlds.