dependence, a protective tissue of relationships, which constitute "coherence" and promote corporate survival. The process brings, too, a greater definiteness of forms and functions: the nebula is shapeless, nebulous; and yet out of it come the elliptical regularity of the planets, the sharp lines of mountain-chains, the specific form and character of organisms and organs, the division of labor and specialization of function in physiological and political structures, etc. And the parts of this integrating whole become not merely definite but diverse, heterogeneous in nature and operation. The primeval nebula is homogeneous—i.e., it consists of parts that are alike; but soon it is differentiated into gases and liquids and solids; the earth becomes here green with grass, there white with mountain-tops, or blue with the multitudinous sea; evolving life begets, out of a relatively homogeneous protoplasm, the varied organs of nutrition, reproduction, locomotion, and perception; a simple language fills whole continents with its multiplying dialects; a single science breeds a hundred, and the folk-lore of a nation flowers into a thousand forms of literary art; individuality grows, character stands out uniquely, and every race and people develops its peculiar genius. Integration and heterogeneity, aggregation of parts into ever larger wholes and differentiation of parts into ever more varied forms: these are the foci of the orbit of evolution. Whatever passes from diffusion to integration and unity, and from a homogeneous simplicity to a differentiated complexity (cf. America, 1600–1900), is in the flow of evolution; whatever is returning from integration to diffusion, and from complexity to simplicity (cf. Europe 200–600 A.D.), is caught in the ebb of dissolution.
Not content with this synthetic formula, Spencer endeavors to show how it follows by inevitable necessity from the natural operation of mechanical forces. There is, first, a certain "Instability of the Homogeneous": i.e., similar parts cannot long remain similar because they are unevenly subjected to external forces; outer parts, e.g., are sooner attacked, like coast-line
