With such presuppositions, it is clear why the Dualist regards his concepts merely as subjective representations of what is really external to his consciousness. The objectively real process in the subject by means of which the percept is produced, and still more the objective relations between things-in-themselves, remain for the Dualist inaccessible to direct knowledge. According to him, man can get only conceptual representations of the objectively real. The bond of unity which connects things-in-themselves with one another, and also objectively with the individual minds (as things-in-themselves) of each of us, exists beyond our consciousness in a Divine Being of whom, once more, we have merely a conceptual representation. The Dualist believes that the whole world would be dissolved into a mere abstract scheme of concepts, did he not posit the existence of real connections beside the conceptual ones. In other words, the ideal principles which thinking discovers are too airy for the Dualist, and he seeks, in addition, real principles with which to support them. Let us examine these real principles a little more closely. The naïve man (Naïve Realist) regards the objects of sense-experience as realities. The fact that his hands can grasp, and his eyes see, these objects is for him sufficient guarantee of their reality. "Nothing exists that cannot be perceived" is, in fact, the first axiom of the naïve man; and it is held to be equally valid in its converse: "Everything which is perceived exists." The best proof for this assertion is the naïve man's belief in immortality and in ghosts. He thinks of the soul as a fine kind of matter perceptible by the senses which, in special circumstances, may actually become visible to the ordinary man (belief in ghosts). In contrast with this, his real, world, the Naïve Realist regards everything else, especially the world of ideas, as unreal, or "merely ideal." What we add to objects by thinking is merely thoughts about the objects. Thought adds nothing real to the percept. But it is not only with reference to the existence of things that the naïve man regards perception as the sole guarantee of reality, but also with reference to the existence of processes. A thing, according to him, can act on another only when a force actually present to perception issues from the one and acts upon the other. The older physicists thought that very fine kinds of substances emanate from the objects and penetrate through the sense-organs into the soul. The actual perception of these substances is impossible only because of the coarseness of our sense-organs relatively to the fineness of these substances. In principle, the reason for attributing reality to these substances was the same as that for attributing it to the objects of the sensible world, viz., their kind of existence, which was conceived to be analogous to that of perceptual reality.