 A more important division is that of “narrow” vs. “wide.” In the literature on propositional attitudes beginning with Putnam (1975), the representational content of an attitude is generally thought to be “wide” in that it does not supervene on the contents of the subject’s head; on this view, two molecularly indistinguishable people could have different belief or desire contents, determined in part by objects in their respective environments. Since according to the representational theory, sensory qualities themselves are real or unreal environmental properties, the theory suggests that the qualities too are wide, and molecularly identical subjects could experience different qualities. Dretske (1996) and Lycan (1996, 2001) have explicitly defended this “phenomenal externalism.” Some other representationalists reject this idea and believe sensory qualities to be narrow, necessarily shared by molecular duplicates. Shoemaker (1994), Horgan (2000), Kriegel (2002b), Levine (2003) and Chalmers (2004) defend narrow representationalism. (Rey (1998) calls his view “a narrow representationalist account of qualitative experience,” but it is not an account of sensory qualities in the present sense; if anything Rey favors the elimination of those qualities.) For some arguments on each side, see Section 4.6.