Splitting hairs ∗

Besides conjoining an assertion into the common ground (Stalnaker 1978), another kind of move that we often propose and accept in discourse is to change our notion of what is a thing and what is the same thing. For example, depending on how a conversation goes, in the middle of it we might start treating ‘a’ and ‘A’ as different letters, while preserving our common knowledge that it is a vowel. (After all, the English alphabet has 26 letters—or is it 52?) Or we might start to distinguish ‘a’ from ‘a’, or even ‘a’ from ‘a’. (After all, the word ‘lava’ contains two vowels—or is it just one?) Similarly in the case of copredication: after agreeing that today ‘lunch was delicious but took forever’ (Asher 2011), we might start to distinguish the food from the event, in order to clarify how we plan to have ‘the same lunch’ tomorrow. This paper begins a study of these moves. They are made by interlocutors such as linguists, meteorologists, and radiologists as they work together to conjure things like grammatical constructions, cold fronts, and tumors from the stuff that is our shared reality. These moves are useful because two interlocutors can agree completely on facts of the matter—be both omniscient, even—yet appear to disagree because they individuate the world into things differently. For example, two linguists may appear to disagree about whether Sita speaks Rama’s language, not because they disagree about how Sita and Rama speak, but because they group idiolects into languages differently. And two meteorologists may appear to disagree about how many cold fronts formed in this country today, only because they distinguish cold fronts, countries, or days differently. I don’t know about you, but this kind of apparent disagreement happens all the time around me. When it does, instead of accusing each other of inaccurate perception, we interlocutors can use these moves to change and align our domains of individuals. These moves are essential for productive conversation, because what individuals we should distinguish and how (Aloni 2000) depends on the current context of the conversation, including what we are trying to do together. Indeed, I can refer to a thing without even myself having an ultimate refinement of it in mind (‘this letter is beautiful’). And as the examples in the previous paragraph suggest, the moves are not specific to words like English ‘same’ and ‘different’ (Beck 2000; Barker 2007).