is not that the method in which science finds its completion? Did it weaken the induction made by Mr. Spencer, to show that the facts are deducible from a general law in the redistributions of matter and motion? Was the induction made by Kepler respecting the laws of planetary motion weakened when Newton proved those laws to be deducible from the law of gravitation? If so, then truths are scientific only so long as they remain empirical generalizations, and become unscientific when they are reduced to the form of rational generalizations. In pursuance of this view we may say that, so long as the geometrical truth, that the square of the hypothenuse of a right-angled triangle is equal to the squares of the other two sides, is recognized as experimentally true, it constitutes a part of real science, but that it becomes metaphysical and worthless when it is shown to follow inevitably from necessary axioms and postulates. The strictures of the author of "German Darwinism," leveled at Spencer as an a priori thinker, thus spend their force against completeness of scientific method. The reproach cast upon him could have had no possible ground, if in elucidating the law of evolution Mr. Spencer had left it in the form of a generalization based upon all orders of phenomena—astronomical, geological, biological, psychological, and sociological—that is, if he had left the work half done. But when the law is explained, or when the universal course of transformation is shown to result from certain universal laws of physical action—laws which are themselves inductively established before they are deductively applied—then Mr. Spencer is to be discredited as a mere speculating metaphysician. It is now admitted as a principle—a universal principle—that force can neither come out of nothing nor disappear into nothing. It is "conserved," say some physicists; it "persists," says Mr. Spencer, and its persistence is an ultimate truth. The laws of physical action which result in evolution, undeniable as they severally are, are shown by Mr. Spencer to be all corollaries from this ultimate truth. They are established by induction, they are explained and verified by proving that they are consequences of a universal principle; therefore Mr. Spencer is metaphysical and unscientific.
The Nation declares that "there is nothing in Spencer's writing relating to what is really honored by men of science (namely, the scientific explanation of the origin of species) that is not to be credited either to Lamarck or Darwin." Lamarck is to be credited with the sagacious perception, and the courageous avowal, in opposition to Cuvier and the whole science of his time, of the doctrine of the variability of species, and the thinness of the partition between species and varieties. He saw many facts that led him to deny the Cuverian dogma of the fixity of species, and he had a strong conviction that their variation was in some way connected with surrounding conditions. That is, Lamarck has the great merit of having perceived the nature of the biological problem that was yet to be solved, but he can hardly be said to have entered upon its solution, Mr. Darwin is to be credited with the sagacious working out of one of the conditions of that problem, namely, the influence of natural selection in giving rise to the diversities of species. But the achievements of both Lamarck and Darwin only bring us to the threshold of the great general question of which they form a part. If their positions are held to be valid, they simply open the door to a new and immense scientific investigation which has for its object to determine the conditions, processes, and causes of evolution. That natural selection is not evolution, but only one of its elements, and that Mr. Darwin has never engaged in the investigation of evolution in its general principles as Science is bound to consider it,
