I am only bound then to sacrifice to others a part of my welfare without hope of recompense:  because it is my duty, and it is impossible to assign definite limits how far that may go.  Much depends on what would be the true want of each according to his own feelings, and it must be left to each to determine this for himself.  For that one should sacrifice his own happiness, his true wants, in order to promote that of others, would be a self-contradictory maxim if made a universal law.  This duty, therefore, is only indeterminate; it has a certain latitude within which one may do more or less without our being able to assign its limits definitely.  The law holds only for the maxims, not for definite actions.

(b) Moral well-being of others (salus moral is) also belongs to the happiness of others, which it is our duty to promote, but only a negative duty.  The pain that a man feels from remorse of conscience, although its origin is moral, is yet in its operation physical, like grief, fear, and every other diseased condition.  To take care that he should not be deservedly smitten by this inward reproach is not indeed my duty but his business; nevertheless, it is my duty to do nothing which by the nature of man might seduce him to that for which his conscience may hereafter torment him, that is, it is my duty not to give him occasion of stumbling.  But there are no definite limits within which this care for the moral satisfaction of others must be kept; therefore it involves only an indeterminate obligation.

IX.  What is a Duty of Virtue?

{Introduction ^paragraph 85}

Virtue is the strength of the man’s maxim in his obedience to duty.  All strength is known only by the obstacles that it can overcome; and in the case of virtue the obstacles are the natural inclinations which may come into conflict with the moral purpose; and as it is the man who himself puts these obstacles in the way of his maxims, hence virtue is not merely a self-constraint (for that might be an effort of one inclination to constrain another), but is also a constraint according to a principle of inward freedom, and therefore by the mere idea of duty, according to its formal law.

All duties involve a notion of necessitation by the law, and ethical duties involve a necessitation for which only an internal legislation is possible; juridical duties, on the other hand, one for which external legislation also is possible.  Both, therefore, include the notion of constraint, either self-constraint or constraint by others.  The moral power of the former is virtue, and the action springing from such a disposition (from reverence for the law) may be called a virtuous action (ethical), although the law expresses a juridical duty.  For it is the doctrine of virtue that commands us to regard the rights of men as holy.