But just as there are some wants of the body which every one has to satisfy by himself, so every one has to know certain scientific facts which are not the prerogative of any special science. This is true of the faculty of human understanding. The knowledge and study of this theory cannot be left to any particular guild. Lassalle justly says: "Thinking itself has become a special trade in these days of division of labor, and it has fallen into the worst hands, those of our newspaper writers." He thus urges us not to acquiesce in this appropriation any longer, not to submit any more to the harangues of public opinion, but to resume thinking for ourselves. We may leave certain objects of scientific research to professionals, but general thought is a public matter which every one should be required to attend to himself. If we could place this general work of thinking on a scientific basis, if we could find a theory of general thought, if we were able to discover the means by which reason arrives at understanding, if we could develop a method by which truth is produced scientifically, then we should acquire for science in general and for our individual faculty of judgment the same certainty of success which we already possess in special fields of science. Kant says: "If it is not possible to harmonize the various co-operators on the question of the means by which their common aim is to be accomplished, then we may safely infer that such a study is not yet on the secure road of science, but will continue to grope in the dark." Now, if we take a look at the sciences, we find that there are many, especially among the natural sciences, which fulfill the requirements of Kant, agreeing unanimously and consciously on certain empirical knowledge and building further understanding on that. "There we know," as Liebig says, "what is to be called a certain fact, a conclusion, a rule, a law. We have touchstones for all this, and every one makes use of them before making known the fruits of his labors. The attempt to maintain any proposition by lawyer's tricks, or the intention to make others believe anything that cannot be proven, are immediately wrecked by the ethics of science." Not so in other fields, where concrete and material things are left behind and abstract, so-called philosophical, matters are taken up, as, for instance, questions of general conceptions of the world and of life, of beginning and end, of the semblance and the essence of things, of cause and effect, of matter and force, of might and right, of wisdom of life, of morality, religion, and politics. Here we find, instead of irrefutable proofs, mere "lawyer's tricks," an absence of reliable knowledge, a mere groping amid contradictory opinions.