It is well known that Mr. Darwin's theory on the Origin of Species has been accepted in Germany more widely, with more absolute faith, and with more vehement enthusiasm, than in the country of its birth. In Germany, more conspicuously than elsewhere, it has itself become the subject of developments as strange and as aberrant as any which it assumes in the history of Organic Life. The most extravagant conclusions have been drawn from it - invading every branch of human thought, in Science, in Philosophy, and in Religion. These conclusions have been preached, too, with a dogmatism as angry and as intolerant as any of the old theologies. It is the fate of every idea which is new and fruitful, that it is ridden to the death by excited novices. We can not be surprised if this fate has overtaken the idea that all existing animal forms have had their ancestry in other forms which exist no longer, and have been derived from these by ordinary generation through countless stages of descent. Although this is an idea which, whether true or not, is entirely subordinate to the larger idea of creation, it usurps in many minds the character of a substitute. This is natural enough.
The theory, or at least the language, of Evolutionists, puts forward a visible order of phenomena as a complete and all-sufficient account of its own origin and cause. However unsatisfactory this may be to the higher faculties of the mind, it is eminently {6} satisfactory to those other faculties which are lower in the scale. It dismisses as needless, or it postpones indefinitely, all thought of the agencies which are ultimate and unseen. Just as in the physical world, some trivial object which is very near us may shut out the whole of a wide horizon, so in the intellectual world, some coarse mechanical conception may shut out all the kingdom of Nature and the glory of it. Two great subjects of investigation lie before us. The first is to ascertain how far the Theory of Evolution represents an universal fact, or only one very partial and fragmentary aspect of a great variety of facts connected with the origin and development of Organic Life. The second and by far the most important inquiry, is to estimate aright, or as nearly as we can, the relative place and importance of these facts in the Philosophy of Nature.
Subjects of investigation so rich and manifold as these may well attract all the most varied gifts of the human mind. This they have already done, and there is every indication that they will continue to do so for generations yet to be. Already an immense literature is devoted to them; and every fresh effort of observation and of reasoning seems to open out new and fruitful avenues of thought. The work which is here introduced to the English reader contains an excellent review of this literature, so far as it is represented in the English and German languages. Knowing the author personally, as I have done for many years, I recognize with pleasure in his work all the carefulness of inquiry, and all the conscientiousness of reasoning, which belong to a singularly candid and patient mind.