Philosophy
Modal Logic and the Metaphysics of Possible Worlds
Quick fact
The question of what possible worlds are—whether they are concrete realities, abstract constructions, or merely linguistic fictions—changes which sentences of modal logic are true, such as whether a statement like 'possibly a talking donkey exists' is true.
Why this is interesting
You probably think some things could have been different: you might have been an astronaut, or the sky might be green. But what does that 'could' actually mean?