 Two final problems, however, loom over any such externalist strategies. One is how to provide content to “response-dependent” terms, such as “interesting,” “amusing,” “sexy,” “worrisome,” whose extensions vary greatly with users and occasions. What seems crucial to the contents of such terms is not any externalia that they might pick out, but simply some internal reactions of thinkers that might vary among them even under all conditions, but without difference in meaning. At any rate, there’s no reason to suppose there’s any sort of law that links the same phenomena to different people who find different things “interesting,” “funny,” or even “green” (cf. Russell, 1912; Hardin, 2008). The other problem is how to distinguish necessarily empty terms that purport to refer to (arguably) impossible phenomena such as perfectly flat surfaces, Euclidean figures, fictional characters or immortal souls. An externalist would seem to be committed to treating all such terms as synonymous, despite, of course, the fact that thoughts about them should obviously be distinguished (see Rey, 2009).