morals, * to bring it by itself to completeness, and to require the
public, which wishes for popular treatment, to await the issue of this
undertaking.



* Just as pure mathematics are distinguished from applied, pure
logic from applied, so if we choose we may also distinguish pure
philosophy of morals (metaphysic) from applied (viz., applied to human
nature). By this designation we are also at once reminded that moral
principles are not based on properties of human nature, but must
subsist a priori of themselves, while from such principles practical
rules must be capable of being deduced for every rational nature,
and accordingly for that of man.



Such a metaphysic of morals, completely isolated, not mixed with any
anthropology, theology, physics, or hyperphysics, and still less
with occult qualities (which we might call hypophysical), is not
only an indispensable substratum of all sound theoretical knowledge of
duties, but is at the same time a desideratum of the highest
importance to the actual fulfilment of their precepts. For the pure
conception of duty, unmixed with any foreign addition of empirical
attractions, and, in a word, the conception of the moral law,
exercises on the human heart, by way of reason alone (which first
becomes aware with this that it can of itself be practical), an
influence so much more powerful than all other springs * which may be
derived from the field of experience, that, in the consciousness of
its worth, it despises the latter, and can by degrees become their