The issues between internalism and externalism should be resolved bottom up by such scientific practice, not by advance metaphysics: by seeing whether any good psychological explanations are externalist, not by deciding on a criterion of the mental and using it to sort explanations as constitutive or not. In this context, I’m aware of no appropriate criterion independent of good explanations; to the extent good explanations reveal constitution, a criterion of the constitutive cannot be used to select among good explanations. As I understand it, externalism predicts that some good psychological explanations of the ‘what’ or ‘how’ kinds will be externalist. (p. 5)One can agree with Hurley's methodology, but why suppose that current science does not already weigh in in favor of internalism (anti-EC)?
The advocates of EC have on the table some empirical explanations of certain phenomena, e.g. what is going on when one does long division or when people make gestures and solve problems. So, now advocates and critics are in the process of evaluating those explanations, not a priori or by advance metaphysics, but by empirical methods. Hurley seems to be misrepresenting the nature of (at least some portions of) the current debate.