I. The Antinomy of Practical Reason.
In the summum bonum which is practical for us, i.e., to be
realized by our will, virtue and happiness are thought as
necessarily combined, so that the one cannot be assumed by pure
practical reason without the other also being attached to it. Now this
combination (like every other) is either analytical or synthetical. It
has been shown that it cannot be analytical; it must then be
synthetical and, more particularly, must be conceived as the
connection of cause and effect, since it concerns a practical good,
i.e., one that is possible by means of action; consequently either the
desire of happiness must be the motive to maxims of virtue, or the
maxim of virtue must be the efficient cause of happiness. The first is
absolutely impossible, because (as was proved in the Analytic)
maxims which place the determining principle of the will in the desire
of personal happiness are not moral at all, and no virtue can be
founded on them. But the second is also impossible, because the
practical connection of causes and effects in the world, as the result
of the determination of the will, does not
depend upon the moral
dispositions of the will, but on the knowledge of the laws of nature
and the physical power to use them for one's purposes; consequently we
cannot expect in the world by the most punctilious observance of the
moral laws any necessary connection of happiness with virtue
adequate to the summum bonum. Now, as the promotion of this summum
bonum, the conception of which contains this connection, is a priori a
necessary object of our will and inseparably attached to the moral
law, the impossibility of the former must prove the falsity of the
latter. If then the supreme good is not possible by practical rules,
then the moral law also which commands us to promote it is directed to
vain imaginary ends and must consequently be false.
