Because when we are talking about the modality of the proposition -- its being necessary, possible or impossible -- and not just talking about its truth, then we are also talking about the world as it could or couldn't possibly be, and not just about the world as it is. — Pierre-Normand
For me this is the exact problem. If we were talking about Paris in our world, then we talking about what
it is, not what it might have been or some other world entirely. To talk about our Paris is to exclude all other possibilities and worlds. Modality is what we don't want to talk about if we wish to understand the meaning of our Paris-- I don't want to know if Paris is the capital in some alternate history. I don't want to know if Paris can be a capital or not in some other place. I don't even want to know if Paris can be the capital of France in our world.
Modality doesn't tell me anything. Sure we can talk about it. Paris could be the capital of France in our world, but it leaves out all relevant information. If I say Paris might (or might not) be the capital (which is true), I don't have any information on whether I should treat it as a such. If someone says to me, "Go pick up the delivery in the capital of France," I'm stuck guessing. Paris might be the capital. It might not be the capital. Whether I can make the pick-up is down to a toss up. Is the Paris the capital of France? I have no idea. I'll only be able to tell with the addition of "Paris is the capital of France."
There is an ideality at play within the mainstream understanding of modality. Supposedly, if we can say "Paris being the capital" is a necessary true (in all possible worlds), then we have what we need to know Paris is the capital, otherwise it all still up in the air.
But this analysis ignores how Paris is of our world.
Our Paris cannot be true in all possible worlds. By identity, any other Paris, whether a concept in modal analysis or an alternate world, is a different city. For Paris to the capital in all possible worlds is impossible. Not merely because there might be different states, but rather because our Paris in necessarily tied to our world. To say "Paris is (not) the capital in all possible worlds" or "Paris might be the capital" gets us nowhere. We can't draw what is true about the world from modality-- is the proposition "Paris is the capital of France" true? We don't still know. We won't until we learn whether Paris is the capital.
'Possible worlds' aren't other worlds. It's just a fancy name for ways the world either is (actually) or could have been (counterfactually). It's a device for formalizing semantic theories of modal statements. — Pierre-Normand
Yes. They're all a logical construction-- even the possibility of our own world. In our world, it is true the Paris may or may not be the Capital of France. This possible world is not actual. It's only a logical concept which indicates which states might be actual.
Mainstream modal analysis fails so often because it treats actuality like this possibility. People get caught in the trap of thinking knowing the possible world gives knowledge of the actual world. Everyone starts tripping up over how Paris could (or could not) be the capital of France rather than paying attention whether it is.
Everything necessarily is, in the actual world, as it is in the actual world. This tautology says nothing about something being necessary or contingent simpliciter. Something isn't necessarily true if the world could have been such that it is false. This is what is meant when we say that there is a possible world in which (or at which, as it is usually expressed in the technical literature) it is false. — Pierre-Normand
I know, but that's sort of the point. What use is knowing necessary or contingent simpliciter if our subject is the actual world? Since modality is only a logical construction, it can't help us if we want to know something about the actual world. All it can do is tell us about the possible one-- e.g. no short, tall, fire snowmen who are made of only sand. We can use it to disregard the existence of contradictory or incoherent states, but that's it. If is's not necessary by logic, the possible world can't make comment. So why exactly are we trying to use it to tell whether or not Paris is the capital of France in the actual world?
That's not very philosophically interesting. — Pierre-Normand
I think it's the most philosophically interesting relation to modality. It represents the logic a describing the world. For us to say,
logically, the capital of France is Paris, we need to now about Paris in our world. If I am to know where to pick-up the delivery, what I need to know is that Paris is the capital of France in the actual world. Far from being trivial, it points out
the most important thing about knowledge: if it's of the actual world, then it must be knowledge of the actual world. We can't get there with modality. Possible worlds won't tell us anything about the actual world.