 The tendencies to find room for motive and character in the area of imperfect duty, and to assimilate virtue with continence, resurface in the writings of several moral philosophers of the 17th and 18th centuries. Immanuel Kant (1724–1804) is an illustrative case. In the Metaphysics of Morals, Kant divides moral philosophy into two domains, that of justice or law on the one hand (the Doctrine of Right), and that of ethics or virtue on the other (the Doctrine of Virtue). The duties that form the subject matter of the Doctrine of Right are like the natural law theorists’ perfect duties: they are precise, owed to specifiable others, and can be legally enforced. They require that we take or forego certain actions. Other duties (which form the subject matter of the Doctrine of Virtue) are duties to adopt certain ends. Many of them are imperfect, in that they do not specify how, when, or for whom (in the case of duties to others) they should be achieved. Examples are the duty not to let one’s talents rust or the duty not to deny help to others. Because we cannot be compelled to adopt ends, but must do so from free choice, these duties are not legally enforceable. They require inner, not outer, legislation, so we must impose them on ourselves. Because, according to Kant, we are always fighting against the impulses and dispositions that oppose the moral law, we need strength of will and self-mastery to fulfill our imperfect duties. This self-mastery Kant calls courage. 