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.

{INTRODUCTION ^paragraph 90}

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