This enlargement of the notion of duty beyond that of external freedom and of its limitation by the merely formal condition of its constant harmony; this, I say, in which, instead of constraint from without, there is set up freedom within, the power of self-constraint, and that not by the help of other inclinations, but by pure practical reason (which scorns all such help), consists in this fact, which raises it above juridical duty; that by it ends are proposed from which jurisprudence altogether abstracts.  In the case of the moral imperative, and the supposition of freedom which it necessarily involves, the law, the power (to fulfil it) and the rational will that determines the maxim, constitute all the elements that form the notion of juridical duty.  But in the imperative, which commands the duty of virtue, there is added, besides the notion of self-constraint, that of an end; not one that we have, but that we ought to have, which, therefore, pure practical reason has in itself, whose highest, unconditional end (which, however, continues to be duty) consists in this:  that virtue is its own end and, by deserving well of men, is also its own reward.  Herein it shines so brightly as an ideal to human perceptions, it seems to cast in the shade even holiness itself, which is never tempted to transgression. * This, however, is an illusion arising from the fact that as we have no measure for the degree of strength, except the greatness of the obstacles which might have been overcome (which in our case are the inclinations), we are led to mistake the subjective conditions of estimation of a magnitude for the objective conditions of the magnitude itself.  But when compared with human ends, all of which have their obstacles to be overcome, it is true that the worth of virtue itself, which is its own end, far outweighs the worth of all the utility and all the empirical ends and advantages which it may have as consequences.

* So that one might very two well-known lines of Haller thus: 

{Introduction ^paragraph 100}

  With all his failings, man is still

  Better than angels void of will.

We may, indeed, say that man is obliged to virtue (as a moral strength).  For although the power (facultas) to overcome all imposing sensible impulses by virtue of his freedom can and must be presupposed, yet this power regarded as strength (robur) is something that must be acquired by the moral spring (the idea of the law) being elevated by contemplation of the dignity of the pure law of reason in us, and at the same time also by exercise.

{Introduction ^paragraph 105}

XI.  According to the preceding Principles, the Scheme of Duties of

Virtue may be thus exhibited

The Material Element of the Duty of Virtue

{Introduction ^paragraph 110}

1 2

Internal Duty of Virtue External Virtue of Duty