end which is in itself a duty. The doctrine of this cannot belong to jurisprudence, but to ethics, since this alone includes in its conception self-constraint according to moral laws.

For this reason, ethics may also be defined as the system of the ends of the pure practical reason. The two parts of moral philosophy are distinguished as treating respectively of ends and of duties of constraint. That ethics contains duties to the observance of which one cannot be (physically) forced by others, is merely the consequence of this, that it is a doctrine of ends, since to be forced to have ends or to set them before one's self is a contradiction.

Now that ethics is a doctrine of virtue (doctrina officiorum virtutis) follows from the definition of virtue given above compared with the obligation,