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February 03, 2006

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dag

Thanks for posting this paper!

I'm confused by your argument on page 19 to the effect that Soames should adopt almost entirely distinct spaces of epistemic and metaphysical possibilities. Why isn't the lesson of your argument just that if you're going to take metaphysically possible worlds to be epistemically possible, then you'd better distinguish what's true at one of those possibilities considered as an epistemic possibility (considered as actual) vs. as a metaphysical possibility (considered as counterfactual)?

That is, it seems to me that Soames should respond that your locution "true(P,w)" is ill-formed, as it doesn't specify whether the world-state in quesiton is being regarded as epistemic or metaphysical. For Soames possibilities (both epistemic and metaphysical) are properties. There are certain (maximal) properties that could have been instantiated (they're metaphysically possible), that we can also conceive of as being instantiated, and that we can't to rule out a priori are instantiated (they're also epistemically possble). All sorts of things would be true if the world does, in fact, instantiate one of these properties (here we're considering the property as an epistemic possibility). Different things would have been true if the world had instantiated one of these properties (considering the peroperty as a metaphysical possibility). In particular, the proposition P iff @P is true NO MATTER WHICH of these properties happens to be instantiated. But it would not have been true if certain of these properties had been instantiated.

What am I missing?

djc

Hi,

I would be delighted if Soames were to respond by distinguishing two ways of evaluating propositions at maximal world-states. But that seems a bit too much to hope for. There's no hint of that sort of two-dimensional evaluation in his book, and he seems to put forward his picture as an alternative to a system with two-dimensional evaluation at a single space of worlds.

On Soames' picture, world-states are said to be epistemically possible or metaphysically possible simpliciter. And on his picture there is no obstacle to having world-states which involves conjunctions of states including [P] and [~@P] -- i.e., the state (of a world) of being such that P is the case, and the state of being such that P is not the case in @. Let W be such a world-state. Then on the face of it, W is epistemically impossible, as (on Soames view) it is epistemically impossible that P&~@P.

Soames can allow that there are distinct relations of epistemic and metaphysical necessitation between propositions, and between world-states and propositions. So he could in principle use those to set up two ways of "evaluating" a proposition P at a world-state W, according to whether the proposition that W obtains epistemically or metaphysically necessitates P. But this will yield nontrivial results only when W is both epistemically and metaphysically possible (if W is epistemically impossible, it epistemically necessitates all propositions, and so on). And if W is a maximal world-state, building in commitments on the truth of P and of @P for all P, then the only maximal world-state that is both epistemically and metaphysically possible will be the actual world-state. To see this, note that any non-actual world-state W builds in [P] for some actually false P. If W builds in [@P], it will be metaphysically impossible; if W builds in [~@P], it will be epistemically impossible.

I suppose there is an alternative picture on which states of the form [@P] are excluded from the relevant "maximal" conjunctive world-states, presumably along with all states involving the truth of propositions relative to other worlds. Then a "maximal" world-state will build in commitments on P (for nonmodal P) but not on @P. Then, if P is contingently false in the actual world, a world-state involving [P] will epistemically necessitate @P (since it is epistemically necessary that P iff @P) but it will metaphysically necessitate ~@P (it is metaphysically necessary that ~@P). On this picture we could admit two sorts of evaluation of propositions in maximal world-states. But (i) there's no hint of the exclusion of modal states like this in Soames' picture (if anything, there's a hint of their inclusion on p. 208); (ii) their exclusion would seem somewhat arbitrary given Soames' starting point, as certainly Soames allows that there are states such as [@P] and doesn't put any other restrictions on the relevant conjunctive states; and (iii) this would yield an even more distinctively two-dimensional picture of evaluation across possible worlds (one that's especially close to the Davies and Humberstone picture). But if Soames would like to go this way, he should feel free!

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