Chris Kennedy and I came up with an idea for making sense of the acquaintance inference and related phenomena in the language of morals. The paper is now forthcoming in Inquiry; the abstract is below and the penultimate draft is available in the Research section:
It has been frequently observed in the literature that assertions of plain sentences containing predicates like fun and frightening give rise to an acquaintance inference: they imply that the speaker has first-hand knowledge of the item under consideration. The goal of this paper is to develop and defend a broadly expressivist explanation of this phenomenon: acquaintance inferences arise because plain sentences containing subjective predicates are designed to express distinguished kinds of attitudes that differ from beliefs in that they can only be acquired by undergoing certain experiences. Its guiding hypothesis is that natural language predicate expressions lexically specify what it takes for their use to be properly “grounded” in a speaker’s state of mind: what state of mind a speaker must be in for a predication to be in accordance with the norms governing assertion. The resulting framework accounts for a range of data surrounding the acquaintance inference as well as for striking parallels between the evidential requirements on subjective predicate uses and the kind of considerations that fuel motivational internalism about the language of morals. A discussion of how the story can be implemented compositionally and of how it compares with other proposals currently on the market is provided.