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?

  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.

  But it does not follow that everything the doing of which is virtue,
is, properly speaking, a duty of virtue. The former may concern merely
the form of the maxims; the latter applies to the matter of them,
namely, to an end which is also conceived as duty. Now, as the ethical
obligation to ends, of which there may be many, is only indeterminate,
because it contains only a law for the maxim of actions, and the end
is the matter (object) of elective will; hence there are many
duties, differing according to the difference of lawful ends, which
may be called duties of virtue (officia honestatis), just because they
are subject only to free self-constraint, not to the constraint of
other men, and determine the end which is also a duty.

  Virtue, being a coincidence of the rational will, with every duty
firmly settled in the character, is, like everything formal, only
one and the same. But, as regards the end of actions, which is also
duty, that is, as regards the matter which one ought to make an end,
there may be several virtues; and as the obligation to its maxim is
called a duty of virtue, it follows that there are also several duties
of virtue.

  The supreme principle of ethics (the doctrine of virtue) is: "Act on
a maxim, the ends of which are such as it might be a universal law for
everyone to have." On this principle a man is an end to himself as
well as others, and it is not enough that he is not permitted to use
either himself or others merely as means (which would imply that be
might be indifferent to them), but it is in itself a duty of every man
to make mankind in general his end.

  The principle of ethics being a categorical imperative does not
admit of proof, but it admits of a justification from principles of
pure practical reason. Whatever in relation to mankind, to oneself,
and others, can be an end, that is an end for pure practical reason:
for this is a faculty of assigning ends in general; and to be
indifferent to them, that is, to take no interest in them, is a
contradiction; since in that case it would not determine the maxims of
actions (which always involve an end), and consequently would cease to
be practical reasons. Pure reason, however, cannot command any ends
a priori, except so far as it declares the same to be also a duty,
which duty is then cared a duty of virtue.

  X. The Supreme Principle of Jurisprudence was Analytical; that of

                     Ethics is Synthetical

  That external constraint, so far as it withstands that which hinders
the external freedom that agrees with general laws (as an obstacle
of the obstacle thereto), can be consistent with ends generally, is
clear on the principle of contradiction, and I need not go beyond
the notion of freedom in order to see it, let the end which each may
be what he will. Accordingly, the supreme principle of jurisprudence
is an analytical principle. On the contrary the principle of ethics
goes beyond the notion of external freedom and, by general laws,
connects further with it an end which it makes a duty. This principle,
therefore, is synthetic. The possibility of it is contained in the
deduction (SS ix).