kind) is a basis of certain duties, that is, of certain actions
which may be consistent with his duty to himself." But we cannot say
that he has a duty of respect for himself; for he must have respect
for the law within himself, in order to be able to conceive duty at
all.





XIII. General Principles of the Metaphysics of Morals in the

{INTRODUCTION ^paragraph 160}

treatment of Pure Ethics



First. A duty can have only a single ground of obligation; and if
two or more proof of it are adduced, this is a certain mark that
either no valid proof has yet been given, or that there are several
distinct duties which have been regarded as one.

For all moral proofs, being philosophical, can only be drawn by
means of rational knowledge from concepts, not like mathematics,
through the construction of concepts. The latter science admits a
variety of proofs of one and the same theorem; because in intuition
a priori there may be several properties of an object, all of which
lead back to the very same principle. If, for instance, to prove the
duty of veracity, an argument is drawn first from the harm that a