have always heretofore shown themselves. Every civilization that has been overwhelmed by barbarians has really perished from internal decay.
This universal fact, the moment that it is recognized, disposes of the theory that progress is by hereditary transmission. Looking over the history of the world, the line of greatest advance does not coincide for any length of time with any line of heredity. On any particular line of heredity, retrogression seems always to follow advance.
Shall we therefore say that there is a national or race life, as there is an individual life—that every social aggregate has, as it were, a certain amount of energy, the expenditure of which necessitates decay? This is an old and widespread idea, that is yet largely held, and that may be constantly seen cropping out incongruously in the writings of the expounders of the development philosophy. Indeed, I do not see why it may not be stated in terms of matter and of motion so as to bring it clearly within the generalizations of evolution. For considering its individuals as atoms, the growth of society is "an integration of matter and concomitant dissipation of motion; during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, and during which the retained motion undergoes a parallel transformation."[1] And thus an analogy may be drawn between the life of a society and the life of a solar system upon the nebular hypothesis. As the heat and light of the sun are produced by the aggregation of atoms evolving motion, which finally ceases when the atoms at length come to a state of equilibrium or rest, and a state of immobility succeeds, which can be broken in again only by the impact of ex-
- ↑ Herbert Spencer's definition of Evolution, "First Principles," p. 396.
