Sliding from possible worlds semantics to truth

Relativism and strong forms of contextualism assert, from what I gather, that the content of a proposition is not true or false simpliciter, but rather true or false at a time/world/context. A motivation for accepting semantic relativism is the success of possible worlds semantics. It becomes easy to make the move from thinking about possible worlds semantics (specifically, what is true at some possible world) to what is true in the actual world. Quite obviously, there is an underlying assumption here that many find it reasonable to deny: that truthmaker theory of some sort is correct.

If you deny the truthmaker theory for, say, Trenton Merricks’ TSB (truth supervenes on being) account, this slide is wholly illegitimate. Perhaps the truth of a proposition is found in it’s constituent parts or a combination of those parts (the proposition) and not in relation to a possible world. One has a good defeater for analytic relativism if you deny that the truth of a proposition is dependent on a relation to a possible world.

Hilary Putnam’s anti-Skepticism Argument

1) If I am a brain in a vat, I express a falsehood in uttering the sentence “I am a brain in a vat.”
2) If I am not a brain in a vat, I express a falsehood in uttering the sentence “I am a brain in a vat.”
3) I am either a brain in a vat or I am not a brain in a vat.
4) In uttering the sentence “I am a brain in a vat,” I express a falsehood. (From (1), (2) and (3))
5) In uttering the sentence “I am a brain in a vat,” I utter a sentence meaning that I am not a brain in a vat.
.: I am not a brain in a vat. (from (4) and (5))

This is not a very convincing argument. His argument hinges on meaning externalism, and this is where he gets the un-utterability of “I am a brain in a vat”, which actually means something like “I am not an English-speaker in a vat.” Of course, if we actually are brains in a vat then we actually aren’t english-speakers in vats either.

“Simplicity”

…is the name of Herman Cappelen and John Hawthorne’s theory of truth and propositions in their new book Relativism and Monadic Truth. It contains five thesis which “fit together nicely”:

T1: There are propositions and they instantiate the fundamental monadic properties of truth simpliciter and falsity simpliciter.
T2: The semantic values of declarative sentences relative to contexts of utterances are propositions.
T3: Propositions are, unsurprisingly, the objects of propositional attitudes, such as belief, hope, wish, doubt, etc.
T4: Propositions are the objects of illocutionary acts; they are, e.g., what we assert or deny.
T5: Propositions are the objects of agreement and disagreement.

This book is a defense of these theses against contemporary contextualism, but the Simplicity theory contains premises that are challenged on other fronts. David Lewis, for example, argued against all the theses by shoving properties into the heuristic space generally reserved for propositions. But for a young philosopher unfamiliar with these debates within philosophy of language and metaphysics, I have to admit that T1-T5 are tantalizing; they all just seem prima facie true. Here are some utterances that cast doubt on Simplicity:

Tim: A said that there’s a beach nearby [speaking of a location close to Tim].
Jason: B said that there’s a beach nearby [speaking of a location close to Jason].
Didi: A and B said that there’s a beach nearby.

Invariantist accounts of utterances content have a rough time handling these statements. “Says-that” accounts don’t seem to be conveying the same content, which accounts for the awkwardness of Didi’s utterances. I don’t know how to solve these kinds of problems from an invariantist perspective, but I hope there is some solution.