 The second enrichment of the basic extensional semantic framework—the one that is distinctive of two-dimensional semantics—requires us to take possible worlds into account in a different way. To see why this might be necessary for an adequate account of meaning, let’s focus on context-sensitive expressions like ‘I’, ‘here’ or ‘this’. In one respect, these terms function like names, picking out the very same thing in every possible world. For instance, if Hillary Clinton says ‘I could have been president’, her word ‘I’ refers rigidly to the same woman, HC, in every possible world and her claim is true just in case there is a possible way the world could be in which HC is president. In standard possible worlds semantics, then, the intension o of ‘I’ is exactly the same as the intension of the name ‘Hillary Clinton’: a function that yields the individual HC for every possible world. But clearly the English word ‘I’ is not synonymous with the name ‘Hillary Clinton’—for John McCain might utter the sentence ‘I could have been president’ and in his mouth the word ‘I’ would refer rigidly to a different person, JM, in every possible world. What’s distinctive of context-sensitive expressions like ‘I’ or ‘this’ is that they represent different things depending on the context in which they are used. David Kaplan  (1989a)[3]  first brought widespread attention to this phenomenon of context-dependence by proposing his influential two-dimensional semantic theory to clarify the rules governing such expressions.