 Kaplan’s semantic rules for indexicals guarantee that certain sentences will be true whenever they are uttered, and certain inferences will be truth preserving. This account paved the way for Kaplan’s formal logic of indexicals (Kaplan 1989a). In this system, logical validity is defined in terms of different possible contexts of use: a sentence is valid iff it is true in every possible context of use; and an inference is valid iff the truth of the premises ensures the truth of the conclusion in every possible context of use.