But philology, from the point where it goes farther back in search of the roots of language, leaves the safe ground of knowledge and commits itself to the fluctuating ocean of conjectures; and since also the scientific evolution theory has only a hypothetical value, the support of a hypothesis in the one science by a hypothesis in the other naturally adds no weight to its probability, either for the one or the other. Besides, we must not overlook the fact that the very point in the history of the development of languages on which the investigation, as it looks backwards, must at present pause--namely, the existence of linguistic roots--presumes a faculty of abstraction which can not be thought of without self-consciousness. Therefore archaeology, comparative ethnography, and comparative philology, show us quite clearly a _development_, but not an _origin_ of mankind through development. Yet they do show an already existing development of mankind; for all three sciences lead back to starting-points, where mankind already existed with all the essential attributes of mankind, and leave us without answer to our questions as to the conditions lying still farther back. Their results we can {99} without difficulty harmonize with a theory which supposes mankind to have originated by evolution, provided such a theory could be confirmed from another side; but they agree just as well with a contrary theory, which excludes the origin of mankind by gradual development. Taking, thus, everything into consideration, we come to the conclusion that the evolution theory, like the descent theory, is so far only a hypothesis--and, indeed, a hypothesis which as such has a much more problematical character than the descent theory. For while in regard to the latter we had to say that we have either this explanation or none of the origin of the higher species, with the evolution theory there is not even room for this alternative. For even in case of its failure, a descent of one species from another through heterogenetic generation is certainly very possible. Besides, it is not only possible, but even probable, that both theories--that of heterogenetic generation and that of gradual development--may have to share with one another in the explanation of the origin of species; and even that, especially for the lowest species and for the beginnings of the main types, primitive generation also has its share in the establishment of the paternity.