Quote of the Week, 2015-01-07

Here, therefore, we treat not of ends which man actually makes to himself in accordance with the sensible impulses of his nature, but of objects of the free elective will under its own laws- objects which he ought to make his end. We may call the former technical (subjective), properly pragmatical, including the rules of prudence in the choice of its ends; but the latter we must call the moral (objective) doctrine of ends. This distinction is, however, superfluous here, since moral philosophy already by its very notion is clearly separated from the doctrine of physical nature (in the present instance, anthropology). The latter resting on empirical principles, whereas the moral doctrine of ends which treats of duties rests on principles given a priori in pure practical reason.

III. Of the Reason for conceiving an End which is also a Duty, The Metaphysical Elements of Ethics, by Immanuel Kant

Translated by Thomas Kingsmill Abbott

Retrieved from Project Gutenberg

There is no such thing as "pure practical reason", unless we include reasoning whose beginning is based in empirical knowledge. By itself, reasoning is manipulating hypotheses into conclusions. It offers no guarantee of the truth of these hypotheses, just the occasional ability to possibly discover that certain combination of hypotheses can't be true at the same time. Even that is not a reliable occurrence.