answer to this question was suggested on observing the changes passed through by every unfolding plant and animal. Immeasurably as do the multitudinous kinds of organisms differ from one another, yet the unfoldings of them proceed in similar ways. The detailed changes gone through are infinitely varied, but the general change is the same for all. It has since become apparent that the abstract formula expressing this transformation in all living things, also expresses the transformation which is, and has been, in progress everywhere. The Solar System, in passing from its primitive state to its present state, has exemplified it; and, if we accept Lord Kelvin's conclusion respecting the dissipation of its energy and consequent ultimate fate, it will continue to exemplify it. The transformation of the Earth from those early stages in which its surface began to solidify, down to its present stage, has likewise conformed to the general law. Among living things it is conformed to not only in the unfolding of every organism, but also, if we draw the conclusion pointed to above, by the organic world in general, considered as an aggregate of species. The phenomena of mind, in rising from its lowest forms in inferior creatures up to its form in Man, and again in rising from the lowest human form to the highest, illustrate it. It is again illustrated by the successive stages of social progress, beginning with groups of savages and ending with civilized nations. And we see it no less displayed in all the products of social life—in language, in the industrial arts, in the development of literature, in the genesis of science.
Is this inductive generalization capable of deductive verification? Does this uniformity of process result from uniformity of cause? The answer is—Yes. As the changes universally in progress now and through all past time have resulted in transformations having certain common traits, so also, in the actions everywhere producing them, there are certain common traits. However vast or however minute, every aggregate is like every other aggregate in being subject to the actions of outer things and in having parts that act on one another. Be it the Solar System, which by its motion through space shows that the Stellar Universe around influences it, and which shows that its component bodies influence one another, or be it an infusorium exposed to currents and to living things in the surrounding water, and made up of interdependent organs, we are equally shown that external incident forces affect everything, and that everything is affected by the mutual actions of its parts. But if there is a fundamental unity in the relations of aggregates to their environments and of their components to one another, there must also be a fundamental unity in the processes of change set up in all cases. Hence, then, a certain community of character in the
