Kant had divided reality into radically distinct opposites of subjectivity and objectivity. The thinking subject may observe the world and study physical objects, but he will never get to an understanding of what the object is apart from human conception. All logical formulations to understand an object become themselves extensions of the observing subject; the subject merely finds that the harder he tries, the more he ends up investigating not the object itself, but his own conscious constructions of the object. The object as it is in-itself forever remains outside the realm of human knowledge and speculation. In other words, subjectivity and objectivity are essentially divorced, and can never be united.
Kant took this idea in many directions, particularly in the field of faith and morals. Kant argued that God as an object can never be known. Any argument for the proof of God would have to be drawn both from predicates not inherently contained in the idea of God, and principles established prior to sense experience—collectively, what Kant called synthetic and a priori judgments. Kant dismantled Anselm’s ontological proof, arguing that existence is not a predicate, and that positing pure existence does not ensure the actual existence of the object with any necessity. However, this opened the way to fuller freedom of the individual. Kant not only denied that any logical proof of God was possible, but he went further and asserted that no logical proof should be possible; if the human will is truly free and unfettered, than belief in God should never be a compulsion of logic.
Quite interestingly, the father of modern rationalism held that faith in God could only be a free, a-rational movement of the will.
