It seems to me that monist sentence theories are too implausible, but might it not nonetheless be the case that some sentences are true/false? In this essay I will discuss sentences as secondary truth bearers.
I can see that it has some pragmatic value to say that sentences are also sometimes true/false in addition to propositions. The pragmatic value is that it makes it easier to talk about certain things without having to use complex phrases like “the proposition expressed by (the sentence) is true (or false)”. Perhaps this is a good enough reason to posit that sentences also in some cases have the properties true/false.
An alternative solution is to invent some shorthands for talking about propositions expressed. See (N. Swartz, R. Bradley, 1979).
The problem I see with it is that of parsimony. “Entities must not be multiplied beyond necessity” (Wiki). Is that not exactly what we are doing? At least if properties are entities. I think they are since entity is the most inclusive set (similar to “thing”)1. But perhaps it is not as problematic to multiply properties as it is to multiply other kinds of entities in an explanation. I don’t know.
What are the conditions for a sentence being true/false?
This is how I see understand the position:
A sentence is true iff it expresses exactly one proposition and that proposition is true.
A sentence is false iff it expresses exactly one proposition and that proposition is false.
The phrase “ expresses exactly one proposition” seems to avoid the ambiguity problem that I wrote about earlier.
1Yes, I am aware of Russell’s paradox that may arise when defining sets like this. I’m working on a ‘solution’.