 How do we determine which theory is correct? Traditional philosophical methods of conceptual or linguistic analysis can give us some guidance, indicating that some accounts offer a better fit with the ordinary concept of happiness. Thus it has been argued that hedonism is false to the concept of happiness as we know it; the intuitions taken to support hedonism point instead to an emotional state view (Haybron 2001). And some have argued that life satisfaction is compatible with profoundly negative emotional states like depression—a suffering artist might not value emotional matters much, and wholeheartedly affirm her life (Carson 1981, Davis 1981b, Haybron 2005, Feldman 2010). Yet it might seem counterintuitive to deem such a person happy. At the same time, people do sometimes use ‘happiness’ to denote states of life satisfaction: life satisfaction theories do seem faithful to some ordinary uses of ‘happiness’. The trouble is that HAPPINESS appears to be a “mongrel concept,” as Ned Block (1995) called the concept of consciousness: the ordinary notion is something of a mess. We use the term to denote different things in different contexts, and often have no clear notion of what we are referring to. This suggests that accounts of happiness must be somewhat revisionary, and that we must assess theories on grounds other than simple fidelity to the lay concept of happiness—“descriptive adequacy,” in Sumner’s (1996) terms. One candidate is practical utility: which conception of happiness best answers to our interests in the notion? We talk about happiness because we care about it. The question is why we care about it, and which psychological states within the extension of the ordinary term make the most sense of this concern. Even if there is no simple answer to the question what happiness is, it may well turn out that our interests in happiness cluster so strongly around a particular psychological kind that happiness can best, or most profitably, be understood in terms of that type of state (Haybron 2003). Alternatively, we may choose to distinguish different varieties of happiness. It will be less important how we use the word, however, than that we be clear about the nature and significance of the phenomena that interest us.