The Metaphysical Elements of Ethics

"If there exists on any subject a philosophy (that is, a system of
rational knowledge based on concepts), then there must also be for this
philosophy a system of pure rational concepts, independent of any condition of
intuition, in other words, a metaphysic. It may be asked whether metaphysical
elements are required also for every practical philosophy, which is the doctrine
of duties, and therefore also for Ethics, in order to be able to present it as a
true science (systematically), not merely as an aggregate of separate doctrines
(fragmentarily). As regards pure jurisprudence, no one will question this
requirement; for it concerns only what is formal in the elective will, which has
to be limited in its external relations according to laws of freedom; without
regarding any end which is the matter of this will. Here, therefore, deontology
is a mere scientific doctrine (doctrina scientiae)."

- Excerpted from "The Metaphysical Elements of Ethics"