he followed Leibnitz in referring to a priori principles of reason with which it was somehow charged. "La vérité des choses sensibles se justifie par leur liaison, qui dépend des vérités intellectuelles, fondles en raison,"[1] says Leibnitz. And Kant's summary explanation in the Prolegomena reads like a comment on this passage. The reader who has hitherto considered experience as a mere aggregate or empirical synthesis of perceptions, is invited to reflect that it goes much further than these, as it gives empirical judgments universal validity, which can come only from a pure synthesis of the understanding a priori. "Experience consists in the synthetical connexion of phenomena (perceptions) in consciousness, so far as this connexion is necessary. Hence the pure concepts of the understanding are those under which all perceptions must be subsumed ere they can serve for judgments of experience, in which the synthetical unity of the perceptions is represented as necessary and universally valid."[2]
But suppose one denies that any synthesis of perceptions can be necessary and universally valid. Suppose the previous question to be raised, whether any proposition whatever can have universal and necessary validity. What then? Well, for Kant, the scion of rationalism, such a doubt would be inconceivable. For his part, he never saw beyond the Leibnitzian opposition of "truths of fact" and "truths of reason." The former were "contingent," the latter "necessary and eternal." The former were derived from experience. Of the latter Leibnitz held that their truth comes from the understanding alone; truth infallible and unchanging cannot be demonstrated by the senses. Kant never deserted this position. And, as we have seen, he also fortified it with a Leibnitzian construction of experience on an a priori basis. For him as for Leibnitz it remained self-evident, that "general principles enter into our perceptions (pensees), of which they form the soul and band of union,"[3] (l'âme et la liaison), and that, accordingly, "the mind
