"The nature of natural history," says F. W. Bessell, "lies in the fact that it does not consider phenomena as facts in themselves, but looks for their causes. The knowledge of nature is thus reduced to the minimum number of facts." But the causes of the phenomena of nature had been investigated even before the age of natural history. The characteristic mark of natural history is not so much that it investigates causes, but that the causes which it investigates have a peculiar nature and a particular quality. Inductive science has materially changed the conception of causes. It has retained the term, but uses it in a different sense from that employed by speculation. The naturalist conceives of causes differently within his special field and outside of it; here, outside of his specialty, he frequently indulges in introspective speculation, because he understands science and its cause in a concrete, but not in a general way. The unscientific forces are of a supernatural make-up, they are transcendental spirits, gods, forces, little and big goblins. The original conception of causes is an anthropomorphic one. In a state of inexperience, man measures the objective by a subjective standard, judges the world by himself. Just as he creates things with conscious intent, so he attributes to nature his human manner, imagines the existence of an external and creative cause of the phenomena of sense perception, similar to himself who is the special cause of his own creations. This subjective mood is to blame for the fact that the struggle for objective understanding has so long been in vain. The unscientifically conceived cause is a speculation of the _a priori_ kind. If the term understanding is retained for subjective understanding, then objective science differs from it in that such a science penetrates to the causes of its objects not by faith or introspective speculation, but by experience and induction, not _a priori_, but _a posteriori_. Natural science looks for causes not outside or back of nature's phenomena, but within or by means of them. Modern research seeks no external creator of causes, but rather the immanent system, the method or general mode of the various phenomena as they are given by succession in time. The unscientifically conceived cause is a "thing in itself," a little god who generates his effects independently and hides behind them. The scientific conception of causes, on the other hand, looks only for the theory of effects, the general element of phenomena. To investigate a cause means then to generalize a variety of phenomena, to arrange the multiplicity of experienced facts under one scientific rule. "The knowledge of nature is thus reduced to the minimum number of facts."