In fact, so far as practical reason is taken as dependent on pathological conditions, that is, as merely regulating the inclinations under the sensible principle of happiness, we could not require speculative reason to take its principles from such a source. Mohammed's paradise, or the absorption into the Deity of the theosophists and mystics would press their monstrosities on the reason according to the taste of each, and one might as well have no reason as surrender it in such fashion to all sorts of dreams. But if pure reason of itself can be practical and is actually so, as the consciousness of the moral law proves, then it is still only one and the same reason which, whether in a theoretical or a practical point of view, judges according to a priori principles; and then it is clear that although it is in the first point of view incompetent to establish certain propositions positively, which, however, do not contradict it, then, as soon as these propositions are inseparably attached to the practical interest of pure reason, it must accept them, though it be as something offered to it from a foreign source, something that has not grown on its own ground, but yet is sufficiently authenticated; and it must try to compare and connect them with everything that it has in its power as speculative reason. It must remember, however, that these are not additions to its insight, but yet are extensions of its employment in another, namely, a practical aspect; and this is not in the least opposed to its interest, which consists in the restriction of wild speculation. Thus, when pure speculative and pure practical reason are combined in one cognition, the latter has the primacy, provided, namely, that this combination is not contingent and arbitrary, but founded a priori on reason itself and therefore necessary. For without this subordination there would arise a conflict of reason with itself; since, if they were merely co-ordinate, the former would close its boundaries strictly and admit nothing from the latter into its domain, while the latter would extend its bounds over everything and when its needs required would seek to embrace the former within them. Nor could we reverse the order and require pure practical reason to be subordinate to the speculative, since all interest is ultimately practical, and even that of speculative reason is conditional, and it is only in the practical employment of reason that it is complete. {BOOK_2|CHAPTER_2 ^paragraph 30} IV. The Immortality of the Soul as a Postulate of Pure Practical Reason.