2. The realm of things-in-themselves is not to Kant the realm of knowledge. By things-in-themselves Kant distinctly does not mean things-for-us, not material bodies, not nature objects. It must be remembered that Kant has plundered the material realm of the dualist. The things-in-themselves which are left behind as a residuum lie outside all sense-perception and so beyond all knowledge. A divine intelligence might have the things-in-themselves as objects of knowledge, but not we human beings. The thing-in-itself is the unknown and unknowable. But if this realm of things-in-themselves is so absolutely independent of us that we cannot in any way know it, how can we say that it exists? Kant replies to this: while we cannot say _what_ a thing-in-itself is, we are obliged to say _that_ it is. For although beyond even our sense-perception, it stands as a necessary postulate to perception, as a mere “problem.” Kant also calls things-in-themselves Noumena, and regards them as “limiting concepts” to the divine non-sensuous intelligence. Their reality is as little to be denied as affirmed. 3. Kant pointed out that between or beside the realm of subjectivity and that of the things-in-themselves lies the realm of human knowledge, which we in our every-day speech call physical nature, and to which he gave the name “the world of phenomena” or “the world of experience.” The subjective world is apprehended by the individual alone, the world of things-in-themselves is known by no human being, but the world of phenomena is the common object of knowledge of humanity. Phenomena are not things-in-themselves, but things-for-us; they are physical nature, an interrelated totality for us. They constitute not absolute reality, but a reality relative to us. Phenomena are experiences in their relations; such related experiences are objects of knowledge, and in their thoroughly organized and systematic form they constitute nature. Thus the dualism which we ordinarily meet, like the “two world” theory of Wolff, has many differences from this critical theory of Kant with its threefold divisions of one world. One of the most important is that in Kant’s theory the correspondence between states of consciousness and reality has disappeared. Reality touches consciousness only at one point,――at that point where sensations arise. Sensations mark the boundary between unknown reality and conscious life. On the side of reality all is darkness; on the side of conscious life all is the creation of our complex synthetic activity. With the boundary line of sensation as a base, the two realms extend in opposite directions. In value the realm of our conscious life is only relative; that of reality or things-in-themselves is absolute.