Skepticism about moral exemplars

Fundamental Principles of the Metaphysic of Morals primary

In the transition to the metaphysics of morals, Kant argues that experience cannot prove we ever act purely from duty, because motives hide; therefore morality must be grounded in reason a priori, not in empirical examples.

give it the law only for the purpose of providing for the interest of the inclinations, whether singly or at the best in the greatest possible harmony with one another. In fact, it is absolutely impossible to make out by experience with complete certainty a single case in which the maxim of an action, however right in itself, rested simply on moral grounds and on the conception of duty. Sometimes it happens that wit…