Re: Fitch's paradox and OWA

Jan Hidders says...

>I think I see now better your point about the fact that in different
>worlds we might use the same description to refer to things that are
>actually different facts. Your example being "it rains" which refers
>to something different if the different worlds correspond to different
>days. But I would argue that this is from the perspective of someone
>who is outside the model and has some way to identify the different
>worlds independent of what facts hold in them.

Yes, that's true. In ordinary discourse about possibility, we don't explicitly talk about *specific* other worlds. However, I think that for some uses of modal talk, we *do* have an explicit way to characterize the other possible worlds. For example, in a deterministic physical theory (such as Newtonian physics), the various possible worlds are characterized by initial conditions, which are determined by a point in phase space.

>When you are inside the model and in a certain world the
>only way to distinguish them is by looking which facts hold in
>them. For the rain example it could be that in your vocabulary
>you can express what day it is, and then you
>can distinguish the different days, but then you could have formulated
>the fact that you had in mind as "it rains and it is today 5 January
>2010". If the date in your world is not in your vocabulary then you
>have no way of describing the differences between the "it rains"
>proposition in different worlds.

Yes, that's true. But on the other hand, we *do* have the language of "possible, necessary" even though there is no way for us to know what is possible and what is necessary (without knowledge of other possible worlds). So if you just stick to what we can know in *this* world, it seems to me that the only notion of "possibility" is logical consistency. That's a very uninteresting notion of possibility.

To go beyond logical consistency, we have to have some theory about what the other possible worlds are.

>For me the meaning of a proposition is in its pragmatics.

Yes, I understand that. I think for the pragmatics of modal language, the "possibilities" are actually found with one physical world (or the history of that world).

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Daryl Mc