As surely as we know that two mountains cannot be without a valley between them, just so surely do we know that nothing in heaven, on earth, or in any other place can lie outside of the general circle of things. Outside of the worldly world there can be no other little world. A logically constituted human mind cannot think differently. And it is likewise impossible to discover such an outside world by the help of and within the limits of experience, because thought is inseparable from experience and there can be no experience without thought. A man who has a head upon his shoulders--and there can be no man without a head--cannot experience any unworldly metaphysical world. The faculty of experience, which includes the faculty of understanding or perception, is merely empirical. Our settled conviction of the unity of the universe is an inborn logic. The unity of the world is the supreme and most universal category. A closer look at it at once reveals the fact that it carries its opposite, the infinite multiplicity, under its heart or in its womb. The general is pregnant with specialties. This is a comparison, and comparisons limp. A mother has other qualities beside that of motherhood, while the universe, or the absolute generality, is nothing but the bearer, the cause, of all special and separate things. It is "pure" motherhood which can no more be without children than the children without a mother. In this way, no cause can be without effects. A cause without an effect--let us dismiss it. The child is as much a cause in motherhood as it is its effect and product. In the same way the universe has never been, and could not be conceived, without the many special children which it carries in its womb. If thought wishes to make for itself a picture, a conception of the cause of all causes, it must necessarily take cognizance of the effects. Thought may very well separate one from the other, but cannot think correctly without the consciousness that its separating and distinguishing is only a formality. Imagining, conceiving, knowing, perceiving, are so many formalities.[9] But philosophy took its departure from the opposite, the wrong, view. It regarded perceiving, understanding, as the main thing. It did not use science as a formality, as something secondary, as something serving a nature, a cause, a purpose, a higher reason, but it started with the illogical and irrelevant assumption that the specialty of mind, understanding, conceiving, judging, distinguishing, is the primary, supreme, self-constituted cause and purpose, instead of being an element in logic. Even in Hegel's logic, which, by the way, has given us much light on the process of thought, this confounding of the original with the copy is the cause of an almost impenetrable mysticism.