the former motivation source and adopts the latter. Thus what is important about the real core of Mill's argument, that moral motivation is principally grounded on external sanctions, is not that it has a profoundly social component, but what arguments Mill uses to justify his position.
To see what arguments Mill adopts, it is useful to see which ones he rejects, in support of utilitarianism. In particular, Mill rejects the view that any concept of first principles can be based on what he refers to variously as moral instinct, direct moral intuition, or a priori. To do this, he must reject Kant's acceptance of the possibility of inferring a priori ethics (4). Mill's problem with Kant's approach to morality is the fact that it is so indefinite. Instinctive thought and action rely on feelings that might be called prerational or worse, vague. Such feelings are antithetical to reason, which is the exact human capability that serves the practical needs of everyday experience. Human reason as Mill explains it can be developed, and its application can be taught and learned in a practical way. According to Mill, a priori reason seems meant to be applied in real-world terms. But on one hand, it is never clear what a priori reason is attached to. That is what Mill means when he says, "The medical art is proved to be good by its conducing to health; but how is it possible to prove that health is good?" (4). Thus, on the other hand, it is perfectly possible that an instinctively derived morality could result in a society that behaves in a way that is unrecognizable as moral. This is not because morality derived from a priori reason is bound to be immoral, but rather because such morality, as the outcome purely of the logical exercise of reason, could fall either toward or away from morality as it is usually recognized.
It is because of the deficiencies he finds in "pure" reason, which he equates with instinctive feeling rather than with dedu...