David Lewis spoke of “the philosophy room,” and the term has gained some currency. But in philosophy's house there are many rooms, and one of them, more austere in design and more sparsely furnished than perhaps any of the others, is the ontology room. (The ontology room is not the epistemology room or the philosophy-of-mind room, and it is separated by many rooms and many long corridors from the political-philosophy room.)

Let ‘discussants’ abbreviate ‘participants in discussions in the ontology room’. Discussants converse in a language I will call Tarskian. The vocabulary of Tarskian consists of closed or open sentences and closed or open terms of English (or some natural language) and the sentential connectives, brackets, quantifiers, variables, and identity sign of the vocabulary of first-order logic (so-called) with identity – perhaps supplemented by items from the vocabulary of various well-defined extensions of first-order logic with identity.