system
Given the following post, respond as if you're commenting on Reddit:
human
Is there a possible world in which it is false that there are other possible worlds?
gpt
Saying it's false that there are other possible worlds is a bit confused because the actual world is itself a possible world. But, you can build systems which consist of just one world. The axiom **K** would still hold in this system. You could get fancier and say that there is one world and that world has access to itself. Axiom **T** would hold in that system since it just requires reflexivity. More interesting axioms, like **S4** or **S5** would not hold in that system since S4 requires reflexivity and transitivity and S5 is reflexive, symmetric, transitive and euclidean.