This last point, viz., that there may be things which are "totally" different from one another, is the one which is decidedly rejected by that science which has risen to the eminence of the positive acquisition of philosophy. There can be no natural things which are "totally" different from one another, because they must all of them have in common the quality of being natural. It sounds very commonplace to say that there are no unnatural things in nature. Since the last witch was burnt, everybody is sufficiently enlightened to know that. But the logical conclusions of natural monism have not yet been drawn. True, natural science, properly socalled, is busily engaged in arriving at them. But so much more strife is there in the "science of mind" and there is no other remedy but a well founded theory of understanding which teaches that nature is not alone absolute nature, but also the nature of the absolute. From this doctrine it necessarily follows that all things are not individually independent, but related by sex, dependent children, "predicates" of the monistic unity of the world. "The arch fountain of the human spirit," says Dittes, "is perception.... Whether perception as such discloses to us the true nature of things, or whether it makes us familiar only with their phenomena, this is not to be discussed by logic." The practical pedagogue who confines himself to the education of children's brains or who wishes at most to influence such teachers as educate children's brains, is quite right in being satisfied with the old traditional Aristotlean logic. But in the school of the human race, this logic has not been sufficient. For this reason the philosophers have broached the question whether perception, "the arch fountain of the human spirit," is a true or a deceptive fountain. The product of the philosophical investigation which we here offer amounts to the declaration that the logicians are greatly mistaken about the "arch fountain." It is a cardinal error of ancient logic to regard perception as the ultimate source from which the human mind dips its knowledge. It is nature which is the ultimate source, and our perception is but the mediator of understanding. And its product, recognized truth, is not truth itself, but merely a formal picture of it. Universal nature is the arch fountain, is the eternal and imperishable truth itself, and our perception, like every other part of universal existence, is only an attribute, a particle of absolute nature. The human mind, with whose nature logic is dealing, is no more an independent thing than any other, but simply a phenomenon, a reflex or predicate of nature. To confound true perceptions or perceived truths with general truth, with the _non plus ultra_ of all truths, is equivalent to regarding a sparrow as _the_ bird in general, or a period of civilization as civilization itself, which would mean the closing of the door to all further development.