Far be it from me as a one-sided advocate of scientific interests to blame this period of enthusiastic excitement; we have, in fact, to thank it for the moral force which broke the Napoleonic yoke; we have to thank it for the grand poetry which is the noblest treasure of our nation; but the real world retains its right against every semblance, even against the most beautiful; and individuals, as well as nations, who wish to rise to the ripeness of manhood must learn to look reality in the face, in order to bend it to the purpose of the mind. To flee into an ideal world is a false resource of transient success; it only facilitates the play of the adversary; and when knowledge only reflects itself, it becomes unsubstantial and empty, or resolves itself into illusions and phrases. Against the errors of a mental tendency, which corresponded at first to the natural soaring of a fresh youthful ambition, but which afterwards, in the age of the Epigones of the Romantic school and of the philosophy of Identity, fell into sentimental straining after sublimity and inspiration, a reaction took place, and was carried out not merely in the regions of science, but also in history, in art, and in philology. In the last departments, too, where we deal directly with products of activity of the human mind, and where, therefore, a construction _à priori_ from the psychological laws seems much more possible than in nature, it has come to be understood that we must first know the facts, before we can establish their laws.