If we call a cream puff a tidbit and rye bread a food without remembering that every food is a tidbit and every tidbit food, and if we ignore the fact that both of them, in spite of their difference, belong to the same category and are, therefore, related, then we lack logic. And logic is lacking whenever the fact is ignored that all things without exception: substances, forces, or qualities of the world, are chips of the same block, finite parts of the infinite, which is the only truth and reality. That insects, fishes, birds, and mammals form one and the same animal kingdom, is an old story which has long been patched up by the logical instinct. Darwin did not only enrich the natural sciences, but also perform an invaluable service for logic. In proving how amphibia developed into birds, he bored a hole into the hitherto fixed order of classification. He brought motion, life, spirit into the zoological swamp. In case you should not be familiar enough with Darwin's work to understand my allusions, I will enter a little more deeply into the matter in a few sentences. The zoologists knew well enough that all species of animals belonged to the animal kingdom; but this classification was a mechanical affair. Now the "Origin of Species," which demonstrates that the zoological classification is not constant but variable, which outlines the actual transition from one species of animals to another, reveals at the same time that this alignment of all animal species in one kingdom is not only a logical mechanism, but also a fact of actual existence. This classification of all animals from the minutest to the most gigantic in one kingdom appeared before the time of Darwin as an order which had been accomplished by thought alone, while after him it was known as an order of nature. What the zoologists did to the animal kingdom, must be done by the logician to existence in general, to the cosmos. It must be shown that the whole world, all forms of its existence, including the spirit, are logically or monistically connected, related, welded together. A certain narrow materialism thinks that everything is done and said when the inter-connection between thought and brain is pointed out. A good many things may still be discovered by the help of the dissecting knife, microscope, and experiment; but this does not make the function of logic superfluous. True, thought and brain are connected, just as intimately as the brain is related to the blood, the blood with oxygen, etc.; but moreover thought is connected quite as intimately with all other things as all physical objects are. That the apple is not alone dependent on the stem which attaches it to the tree, but also on sunshine and rain, that these things are not one-sidedly but universally connected, this is what logic wants to teach you particularly in regard to the spirit, the thought.