Kant's system of duties constitutes a Doctrine of Virtue because the duties also indicate what kinds of attitudes, dispositions and feelings are morally virtuous or vicious.
Allen W. WoodWe can establish empirical criteria for free actions, and investigate human actions on the presupposition we are free.
Allen W. WoodKant's description of most ethical duties reads more like a description of moral virtues and vices. Once we see this, we see that Kantian ethics is indeed a kind of virtue ethics, and that it does not "divide the heart from the head" (to anticipate one of your later questions) but instead recognizes the deep truth that reason and emotion are not opposites.
Allen W. Wood