 In the simplest case, where we have a theory T that introduces one new name t, Lewis says that t denotes the x such that T[x], where T[x] is the sentence we get by (a) converting T to a single sentence, perhaps a single long conjunction, and (b) replacing all occurrences of t with the variable x. That is, if there is a unique x such that T[x], t denotes it, and t is denotationless otherwise. (Note that it isn’t meaningless, but it is denotationless.)