BOOK2"CHAPTER2 ^paragraph 10

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.