Kaplan’s official argument in “Demonstratives” for Temporalism, the view that some English sentences express propositions that can vary in truth value across time, is the so-called Operator Argument: temporal operators, such as “sometimes”, would be vacuous without such propositions.
Equally important is the argument from compositionality. Without temporal propositions, the sentences
(I) It is raining where John is
(2) It is raining where John is now
would express the same proposition. But they embed differently:
(3) Sometimes, it is raining where John is
(4) Sometimes it is raining where John is now
(3) and (4) express distinct propositions, so if they both are of the form “Sometimes, p”, and if (1) and (2) express the same proposition, we have a violation of compositionality.
In this talk it is shown that with Switcher Semantics, which allows for a generalized form of compositionality, we can have the result that (1) and (2) agree in content when unembedded (assertoric content) but differ in content when embedded under temporal operators (ingredient sense).
We can also show that Switcher Semantics, over Kaplan’s models, preserves the validities in the Logic of Demonstratives. All in all, the arguments for Temporalism are substantially undermined.