system
Given the following post, respond as if you're commenting on Reddit:
human
There is no possible world in which the world does not exist. Does that mean that the world necessarily exists?
gpt
If we follow Lewis' conception of necessity and possiblity, then something similar to what you are talking about does follow.

According to Lewis, we analyze "Necessarily x" as "In all possible worlds, x". That means we would have to understand "The world necessarily exists" as "In all possible worlds, the world (that world?) exists", which would obviously come out as true.

But let's not get carried away with the result, which does not establish anything very interesting by itself. It does not, for example, establish that *this* world necessarily exists, or (generalized) that any particular world existst necessarily. Likewise, it does not establish that there are no empty worlds. Since in Lewis' framework, worlds are described in terms of sets, they don't "disappear" if they are empty.

But Metaphysics has moved on quite a bit since Lewis. While his account is still a useful way to analyze necessity and possibility, philosophers have become more sceptical that it's all there is to say about modality. Kit Fine, for example, introduced the notion of a non-worldly necessity in his paper "Necessity and Non-Existence" (2004). According to Fine, there are certain facts that are true regardless of the world at which they are evaluated, like your statement of "The world existst.", but there are also statements that do not need a world context to be meaningfully evaluated, like "2+2=4". You can see that, while "The world existst" is true in all world contexts, and thus necessarily true, it is not true regardless of there being a world context, and thus not (what Fine calls) transcendentally true.

There is good reason to think that there is more to modality than possible worlds, and you should not therefor put too much weight on your result. But it is a correct result, given Lewis' account.