* Man, however, as at the same time a moral being, when he considers himself objectively, which he is qualified to do by his pure practical reason, (i.e., according to humanity in his own person). finds himself holy enough to transgress the law only unwillingly; for there is no man so depraved who in this transgression would not feel a resistance and an abhorrence of himself, so that he must put a force on himself.  It is impossible to explain the phenomenon that at this parting of the ways (where the beautiful fable places Hercules between virtue and sensuality) man shows more propensity to obey inclination than the law.  For, we can only explain what happens by tracing it to a cause according to physical laws; but then we should not be able to conceive the elective will as free.  Now this mutually opposed self-constraint and the inevitability of it makes us recognize the incomprehensible property of freedom.

The impulses of nature, then, contain hindrances to the fulfilment of duty in the mind of man, and resisting forces, some of them powerful; and he must judge himself able to combat these and to conquer them by means of reason, not in the future, but in the present, simultaneously with the thought; he must judge that he can do what the law unconditionally commands that be ought.

Now the power and resolved purpose to resist a strong but unjust opponent is called fortitude (fortitudo), and when concerned with the opponent of the moral character within us, it is virtue (virtus, fortitudo moralis).  Accordingly, general deontology, in that part which brings not external, but internal, freedom under laws is the doctrine of virtue.

{Introduction ^paragraph 10}

Jurisprudence had to do only with the formal condition of external freedom (the condition of consistency with itself, if its maxim became a universal law), that is, with law.  Ethics, on the contrary, supplies us with a matter (an object of the free elective will), an end of pure reason which is at the same time conceived as an objectively necessary end, i.e., as duty for all men.  For, as the sensible inclinations mislead us to ends (which are the matter of the elective will) that may contradict duty, the legislating reason cannot otherwise guard against their influence than by an opposite moral end, which therefore must be given a priori independently on inclination.

An end is an object of the elective will (of a rational being) by the idea of which this will is determined to an action for the production of this object.  Now I may be forced by others to actions which are directed to an end as means, but I cannot be forced to have an end; I can only make something an end to myself.  If, however, I am also bound to make something which lies in the notions of practical reason an end to myself, and therefore besides the formal determining principle of the elective will (as contained in law) to have also a material principle, an end which can be opposed to the end derived from sensible impulses; then this gives the notion of an 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.