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.

The evolution theory could only pass beyond the rank of a hypothesis, if we
should succeed in showing the impelling forces of such an origin of species
through development. Such an attempt can be made in two ways--the
metaphysical and the scientific-empirical. The first, the metaphysical,
although it may be justified in its general principles, will always, from
the point at which it attempts to approach the concrete questions as {100}
to the origin of single species, expos