we
must ascertain the character common to these modifications--the law to
which they all conform. And similarly in every other case. Leaving out
of sight concomitants and beneficial consequences, let us ask what
progress is in itself.

In respect to that progress which individual organisms display in the
course of their evolution, this question has been answered by the
Germans. The investigations of Wolff, Goethe, and von Baer have
established the truth that the series of changes gone through during the
development of a seed into a tree, or an ovum into an animal, constitute
an advance from homogeneity of structure to heterogeneity of structure.
In its primary stage, every germ consists of a substance that is
uniform throughout, both in texture and chemical composition. The first
step is the appearance of a difference between two parts of this
substance; or, as the phenomenon is called in physiological language, a
differentiation. Each of these differentiated divisions presently begins
itself to exhibit some contrast of parts; and by and by these secondary
differentiations become as definite as the original one. This process is
continuously repeated--is simultaneously going on in all parts of the
growing embryo; and by endless differentiations of this sort there is
finally produced that complex combination of tissues and organs
constituting the adult animal or plant. This is the history of all
organisms whatever. It is settled beyond dispute that organic progress
consists in a change from the homogeneous to the heterogeneous.

Now, we propose to show that this law of organic progress is the law of
all progress. Whether it be in the development of the earth, in the
development of life upon its surface, in the development of society, of
government, of manufactures, of commerce, of language, literature,
science, art--this same evolution of the simple into the complex,
through successive differentiations, holds throughout. From the earliest
traceable cosmic changes down to the latest results of civilization, we
shall find that the transformation of the homogeneous into the
heterogeneous is that in which progress essentially consists.

3. The Stages of Progress[335]

If we regard the course of human development from the highest scientific
point of view, we shall perceive that it consists in educing more and
more the characteristic faculties of humanity, in comparison with those
of animality; and especially with those