Communicating in contextual ignorance

When A utters a declarative sentence in a context to B, typically A can mean a proposition by the sentence, the sentence in context literally expresses a proposition, there are propositions A and B can agree the sentence literally expressed, and B can acquire knowledge from this testimonial exchange. In recent work on linguistic communication, each of these four platitudes has been challenged, and on the same basis: viz. on the ground that exactly which proposition the sentence expressed in context is not discernible given the information provided by the context. I argue that, even if this is true, there will be propositional parts of the proposition expressed by the sentence in context which can be identified and that, consequently, the partial understanding afforded by the existence of such identifiable parts undermines the soundness of the arguments against the platitudes.