gress of the empirical sciences. In the most favorable case, it can claim the value of a hypothesis which has to be put to the proof, whether it can be empirically confirmed and whether we can successfully operate with it in knowing the world of realities. But herewith it leaves the realm of pure philosophy, and makes the question of its right to exist dependent upon the decision of natural science.

Since the decline of the doctrines of nature held by Schelling, Steffens, and Hegel, there has come to our knowledge, from the domain of philosophy, but one earnest attempt to explain the origin and development of organisms down to the concrete differences between single types, classes, and even orders and families, from one single metaphysical principle; and this attempt has been made by an antagonist of the descent doctrine. K. Ch. Planck, in "Seele und Geist, oder Ursprung, Wesen und Thätigkeitsform der physischen und geistigen Organisation von den naturwissenschaftlichen Grundlagen aus allgemein fasslich entwickelt" ("Soul and Spirit, or Origin, Nature, and Form of Activity of Phys ical and Intellectual Organization, Clearly Developed from a Scientific Basis"), Leipzig, Fues, 1871, and in "Wahrheit und Flachheit des Darwinismus " ("Truth and Platitude of Darwinism"), Nördlingen, Beck, 1872, makes the "inner concentration" the moving principle of the whole development of the world. He thinks that what belongs to the organism and to the soul has originated and developed up to man and his spiritual nature thus: that the creating centrum of the earth produces individual centra on its periphery, which tend more and more to bring into view the principle of cen

tralization, in its contrast to the purely peripheral form of existence, until it reaches its goal in man, with his centralizing spirit. We have no reason to reject the idea of a principle of concentration in the world and its parts; it is confirmed by observation, and shows itself fruitful in many respects. But in spite of the many ingenious and often suggestive ideas in the works of Planck, we have some doubt about a system which tries to explain the whole concrete abundance of the richness of formations and life-forms in the world, rising higher and higher up to spiritual existence and moral action, from the single idea of concentration, and makes this principle the mys tical and mysteriously acting cause of a whole world and its contents. We doubt at the outset the success of this argument. We have especially the strongest objections to a philosophical system which submits all the contending physical theories of the present to the measure of that concentration principle, and from these purely metaphysical reasons takes side exclusively with the one or the other of the theories, or establishes new theoriesfrom the theories of atoms and ether, of light and heat, down to geological questions as to whether universal revolutions of the world or a continual development took place. The solution of all these questions, in their full extent, we do not attribute to philosophy, but to natural science; although to a natural science which permits philosophy to define the ideas with which it operates and the general principles to which it comes. For this renunciation-which philosophy, however, can not at all escape-it will be the more richly rewarded in this, that it obtains the more certainly for its own work sure and sifted material. But all attempts which can not

$

submit to this renunciation, give only an apparent right to that view which Albert Lange, in his "History of Materialism," defends, when he banishes speculative philosophy to the realm of imagination.

But in rejecting philosophy in the question of the causes of the development and organization of the organic kingdoms, we did not reach the end of the philosophic problems with which we are confronted. This whole question is itself only a segment of the problems before which we stand, and leads of necessity to other questions.

Already within the series of development of the organic world, so far as it is investigated by natural science, we have found and named a point (at the end of § 1, Chap. II, Book I), where the competency of pure natural science comes to an end, and the question arises whether another source of knowledge-i. e., even phiosophy-can not take up the investigation where natural science completes its task. This point was the origin of self-consciousness and of free moral self-determination; consequently, the origin of that which makes man man. Going still farther back on the temporal and ideal scale of organic beings, we arrive at another point, which natural science no longer can explain, and that is the origin of sensation and of consciousness. With the appearance of sensation and consciousness, the animal world came into existence. Moreover, the whole scientific question as to the origin and development of species, so far as we have hitherto treated it, started from initial points where the organic and life already existed; it, therefore, leads of necessity to the further question as to the origin of the organic and of life itself. D. F. Strauss,

in his "Postscript as Preface," thus clearly and simply characterizes these still unfilled blanks in the evolution theory: "There are, as is well known, three points in the rising development of nature, to which the appearance of incomprehensibility especially adheres (to speak more categorically: which have not been explained thus far by anybody). The three questions are: How has the living sprung from that which is without life? the sentient (and conscious) being from that which is without sensation? that which possesses reason (self-consciousness and free will) from that which is without reason?-questions equally embarrassing to thought." But even the question as to the origin of the organic and of life can not be discussed without an investigation, leading us farther back to the question as to the elements of the world in general. The doctrine of atoms, and the mechanical view of the world, are the scientific evidences of the efforts in this direction.

So far as the attempts to solve these four questions start from the results of natural science and, from this starting-point of the known, try to solve the unknown, we will have to assign them in the encyclopædic classification of the sciences, to that department of philosophy which treats the doctrines of nature; and since our whole investigation starts from the Darwinian theories, and only tries to treat of what is properly connected with them, the attempts to solve these four questions offer themselves as the naturo-philosophic supplements of the Darwinian-theories.

After concluding our treatment of them, we shall have to speak of still another view, which presupposes all these attempts at solution to be wholly or nearly suc

cessful, and draws an inference from them which no longer belongs to the realm of natural science, but is a purely metaphysical hypothesis; it is the abolition of the idea of design in nature. In connection with this, finally, we shall have to discuss the name which this view has lately assumed, viz: "Monism."

Whatever further questions may arise, belong either to the special subdivisions of natural science and philosophy, or to theological and ethical problems.