by the moral law, so frequent practice in accordance with this
principle of determination can, at least, produce subjectively a
feeling of satisfaction; on the contrary, it is a duty to establish
and to cultivate this, which alone deserves to be called properly
the moral feeling; but the notion of duty cannot be derived from it,
else we should have to suppose a feeling for the law as such, and thus
make that an object of sensation which can only be thought by the
reason; and this, if it is not to be a flat contradiction, would
destroy all notion of duty and put in its place a mere mechanical play
of refined inclinations sometimes contending with the coarser.

If now we compare our formal supreme principle of pure practical
reason (that of autonomy of the will) with all previous material
principles of morality, we can exhibit them all in a table in which
all possible cases are exhausted, except the one formal principle; and
thus we can show visibly that it is vain to look for any other
principle than that now proposed. In fact all possible principles of
determination of the will are either merely subjective, and
therefore empirical, or are also objective and rational; and both
are either external or internal.



Practical Material Principles of Determination taken as the
Foundation of Morality, are:

{BOOK_1|CHAPTER_1 ^paragraph 105}