Philosophy
The Metaphysics of Possibility and the Transworld Identity Problem
Quick fact
David Lewis famously rejected the idea that the same individual exists in multiple possible worlds, instead proposing 'counterparts'—distinct but similar individuals in other worlds—to avoid the transworld identity problem.
Why this is interesting
You might think that you could have been a teacher instead of a programmer—but in what sense is that 'you' in that other scenario? What makes it the same person?