 Yet another objection to functionalist theories of any sort is that they do not capture the interrelations that we take to be definitive of beliefs, desires, and other intentional states. Whereas even analytic functionalists hold that mental states— and also their contents— are implicitly defined in terms of their (causal or probabilistic) roles in producing behavior, these critics understand intentional states to be implicitly defined in terms of their roles in rationalizing, or making sense of, behavior. This is a different enterprise, they claim, since rationalization, unlike causal explanation, requires showing how an individual's beliefs, desires, and behavior conform, or at least approximate, to certain a priori norms or ideals of theoretical and practical reasoning — prescriptions about which beliefs and desires we should have, how we should reason, or what, given our beliefs and desires, we ought to do. (See Davidson 1980c, Dennett 1978, and McDowell 1985 for classic expressions of this view.) Thus the defining (“constitutive”) normative or rational relations among intentional states expressed by these principles cannot be expected to correspond to causal and probabilistic relations among our internal states, sensory stimulations and behavior, since they constitute a kind of explanation that has sources of evidence and standards for correctness that are different from those of empirical theories (Davidson 1980c). One can't, that is, extract facts from values.