I repeat, then, that we become aware of the outer world in a twofold way, viz., in a concrete, tangible, manifold form, and in an abstract form, which is mental and unitary. To our senses the world appears as a variety of forms. Our brains combine them as a unit. And what is true of the world, holds good of every one of its parts. A sense-perceived unit is a nonentity. Even the atom of a drop of water or the atom of any chemical element, is divisible, so long as it exists at all, and its parts are different and distinct. A is not B. But the concept, the faculty of thought, makes of every tangible or sense-perceived part an abstract whole and conceives of every whole or quantity as a part of the abstract world unit. In order to understand the things in their entirety, we must take them practically and theoretically, with body and mind. With the body we can grasp only the bodily, the tangible, with the mind only the mental, the thinkable. Things also possess mental quality. Mind is material and things are mental. Mind and matter are real only in their inter-relations. Can we see the things themselves? No, we see only the effects of things on our eyes. We do not taste the vinegar, but the relation of the vinegar to our tongue. The result is the sensation of acidity. The vinegar is acid only in relation to our tongue. In relation to iron it acts as a solvent. In the cold it becomes hard, in the heat liquid. It acts differently on different objects with which it enters into relations of time and space. Vinegar is a phenomenon, just as all things are. But it never appears as vinegar by itself. It always appears in connection with other phenomena. Every phenomenon is a product of a subject and an object. In order that a thought may appear, the brain or the faculty of thought is not sufficient in itself. It requires, besides, an object which suggests the thought. From this relative nature of our topic it follows that in its treatment we cannot confine ourselves "purely" to it. Since reason, or the faculty of thought, never appears by itself, but always in connection with other things, we are continually compelled to pass from the faculty of thought to other things, which are its objects, and to treat of their connections. Just as the sight does not see the tree, but only that which is visible of the tree, so does the faculty of thought assimilate only the perceivable image of an object, not the object itself. A thought is a child begotten by the function of the brain in communion with some object. In a thought is crystalized on one side the subjective faculty of thought, and on the other the perceivable nature of an object. Every function of the mind presupposes some object by which it is caused and the spiritual image of which it is. Or vice versa, the spiritual content of the mind is derived from some object which has its own existence and which is either seen or heard, or smelled, or tasted, or felt, in short, experienced.