As all obligation is entirely dependent on a condition, so also is all duty. Both conceptions are very closely related, indeed almost identical. The only difference between them might be said to be that obligation in general may rest on mere force, whereas duty involves the sense of obligation deliberately undertaken, such as we see between master and servant, principal and subordinate, rulers and the ruled.

And since no one undertakes a duty gratis, every duty implies also a right. The slave has no duties, because he has no rights; but he is subject to an obligation which rests on sheer force. In the following Part I shall explain the only meaning which the conception “Duty” has in Ethics.

If we put Ethics in an imperative form, making it a Doctrine of Duties, and regard the