fulfilled. Abundant proof has been given that the law of organic
development formulated by von Baer, is the law of all development. The
advance from the simple to the complex, through a process of successive
differentiations, is seen alike in the earliest changes of the Universe
to which we can reason our way back, and in the earliest changes which
we can inductively establish; it is seen in the geologic and climatic
evolution of the Earth; it is seen in the unfolding of every single
organism on its surface, and in the multiplication of kinds of
organisms; it is seen in the evolution of Humanity, whether contemplated
in the civilized individual, or in the aggregate of races; it is seen in
the evolution of Society in respect alike of its political, its
religious, and its economical organization; and it is seen in the
evolution of all those endless concrete and abstract products of human
activity which constitute the environment of our daily life. From the
remotest past which Science can fathom, up to the novelties of
yesterday, that in which progress essentially consists, is the
transformation of the homogeneous into the heterogeneous.

* * * * *

And now, must not this uniformity of procedure be a consequence of some
fundamental necessity? May we not rationally seek for some all-pervading
principle which determines this all-pervading process of things? Does
not the universality of the _law_ imply a universal _cause_?

That we can comprehend such cause, noumenally considered, is not to be
supposed. To do this would be to solve that ultimate mystery which must
ever transcend human intelligence. But it still may be possible for us
to reduce the law of all progress, above set forth, from the condition
of an empirical generalization, to the condition of a rational
generalization. Just as it was possible to interpret Kepler's laws as
necessary consequences of the law of gravitation; so it may be possible
to interpret this law of progress, in its multiform manifestations, as
the necessary consequence of some similarly universal principle. As
gravitation was assignable as the _cause_ of each of the groups of
phenomena which Kepler generalized; so may some equally simple attribute
of things be assignable as the cause of each of the groups of phenomena
generalized in the foregoing pages. We may be able to affiliate all
these varied evolutions of the homogeneous into the heterogeneous, upon
certai