To the number of modes of relation which the understanding cogitates by means of the categories, the number of pure rational conceptions will correspond.We must therefore seek for, first, an unconditioned of the categorical synthesis in a subject; secondly, of the hypothetical synthesis of the members of a series; thirdly, of the disjunctive synthesis of parts in a system.
There are exactly the same number of modes of syllogisms, each of which proceeds through prosyllogisms to the unconditioned- one to the subject which cannot be employed as predicate, another to the presupposition which supposes nothing higher than itself, and the third to an aggregate of the members of the complete division of a conception.Hence the pure rational conceptions of totality in the synthesis of conditions have a necessary foundation in the nature of human reason- at least as modes of elevating the unity of the understanding to the unconditioned.They may have no valid application, corresponding to their transcendental employment, in concreto, and be thus of no greater utility than to direct the understanding how, while extending them as widely as possible, to maintain its exercise and application in perfect consistence and harmony.