combine our study of their fundamental principles with that of their history. We can here set forth, however, only the chief point of view, the gist of the matter, which will continue to exist and hold good however the analysis of details may turn out. For the kernel of the question may be discussed independently, without involving the particular interests of zoology or biology, though we shall constantly come across particular and concrete cases of the main problem in our more detailed study. The struggle against, and the aversion to ideas and purposes on the part of the nature-interpreters is not in itself directed against religion. It does not arise from any antagonism of natural science to the religious conception of the world, but is primarily an antagonism of one school of science to another, the modern against the mediæval-Aristotelian. The latter, again, was not in itself a religious world-outlook, it was simply an attempt at an interpretation of the processes of nature, and especially of evolution, which might be quite neutral towards religion, or might be purely naturalistic. It was the theory of Entelechies and _formæ substaniales_. In order to explain how a thing had come to be, it taught that the idea of the finished thing, the “form,” was implicit in it from the very beginning, and determined the course of its development. This “form,” the end aimed at in development, was “potentially,” “ideally,” or “virtually” implicit in the thing from the beginning, was the _causa finalis_, the ultimate cause which determined the development. Modern natural science objects to this theory that it offers no explanation, but merely gives a name to what has to be explained. The aim of science, it tells us, is to elucidate the play of causes which brought about a particular result. The hypothetical _causa finalis_ it regards as a mere _asylum ignorantiæ_, and as the problem itself not as its solution. For instance, if we inquire into the present form and aspect of the earth, nothing is advanced by stating that the “form,” the primitive model of the evolving earth was implicit in it from the beginning, and that it gradually determined the phases and transition-stages of its evolution, until the ultimate state, the end aimed at, was attained. The task of science is, through geology, geognosy, mineralogy, geodesy, physical geography, meteorology, and other sciences to discover the physical, chemical, and mechanical causes of the earth’s evolution and their laws, and from the co-operation of these to interpret everything in detail and as a whole.