The asymmetry between mental and physical explanation is accounted for by the greater leniency of physical constitutive principles, not by rationality's uncodifiability

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 science