No More Learning

In fact, even if we did not know that the principle of morality is a pure a priori law determining the will, yet, that we may not assume principles quite gratuitously, we must, at least at first, leave it unde- cided, whether the will has merely empirical principles of determi- nation, or whether it has not also pure a priori principles; for it is           to all rules of philosophical method to assume as decided that which is the very point in question.