He is therefore engaged with principles, formal conceptions, which are subjective and not derived from the knowledge of external phenomena, but which are applied to Nature and Humanity, as the principles according to which Nature and Humanity must regulate themselves. But how are these subjective principles derived? From thought itself? No, for Herr Duehring himself says: the purely ideal realm is limited to logical arrangements and mathematical conceptions (which latter as we shall later see is false). Logical arrangements can only be referred to forms of thought, but we are engaged here only with forms of existence, the external world, and these forms can never be created by thought nor derived from it but only from the external world. Hereupon the entire matter undergoes a change. We see that principles are not the starting point of investigation but the conclusion of it, they are not to be applied to nature and history but are derived from them. Nature and Humanity are not steered by principles, but principles are, on the other hand, only correct so far as they correspond with nature and history. That is just the materialistic conception of the matter, and the opposite, that of Herr Duehring is the idealistic conception, it turns things upside down and constructs a real world out of the world of thought, arrangements, plans and categories existing from everlasting before the world, just like Hegelianism. As a matter of fact, we prefer Hegel's "Encyclopedia," with all its fever phantoms, to the "final truths of the last instance" of Herr Duehring. In the first place, according to Herr Duehring we have the general scheme of the universe which by Hegel is called "logic." Then according to both of them we have the application of this scheme to nature by means of the logical categories, the philosophy of nature, and finally their application to Humanity, by what Hegel calls "the Philosophy of the Spirit." "The inner logical arrangement" of Duehring's scheme brings us therefore logically back to Hegel's "Encyclopedia" from which it is taken with a fidelity which would move that Wandering Jew of the Hegelian school, Professor Michelet of Berlin, to tears. Such a result follows if one takes it for granted that "consciousness," "thought," is something which has existed from the beginning in contradistinction to nature. It would then be of the greatest importance to bring consciousness and Nature, thought and existence, into harmony, to harmonise the laws of thought and the laws of Nature. But one enquires further what are thought and consciousness and whence do they originate. It is consequently discovered that they are products of the brain of man, and that Humanity is itself a product of nature which has developed in and along with its environment; wherefore it becomes self-apparent that the products of the brain of man being themselves, in the last instance, natural products, do not contradict all the rest of Nature but correspond with it.