 If, however, the emphasis here falls on constitutive principles in particular—as surely it must—then two other problems arise. First, McDowell’s reasoning doesn’t tell us what exactly it is about such principles that makes them resistant to reduction, since, as we’ve just seen, that reasoning has failed to distinguish them from empirical concepts in the physical sciences. And second, as noted in  4.2,  Davidson holds that there are constitutive a priori principles underlying the physical sciences which play a similar role there that rationality plays in psychological explanation. So we are still in need of an explanation of why psychology and physics cannot stand in strict lawlike relations. Now, we did note there that such physical constitutive principles are far more lenient than rationality, allowing for a greater variety of empirical content—of what can follow from what. This indeed accounts for an important asymmetry between mental and physical explanation. And McDowell heavily emphasizes this point in his discussion: that it is not merely a brute fact that rationality marks the limits of intelligibility, while physical explanations do bottom out in brute facts (McDowell 1985, 394). However, this point appears to be entirely separable from the distinctive feature of McDowell’s reading of the argument for mental anomalism—it has nothing especially to do with the idea of rationality as uncodifiable in McDowell’s specific sense. In fact, it is the key point behind Kim’s strategy, and it appears to have no essential connection to McDowell’s stronger views about rationality. One can think of rationality as constitutive, as normative and as asymmetrical to the physical in the way just noted—as Kim does—without buying into McDowell’s distinctive picture of it. So it looks like the salvageable part of McDowell’s actual argument for mental anomalism ultimately reduces to Kim’s. Uncodifiability appears to be a red herring.