We have now looked at social evolution, as the product of both those sets of causes—the “_external factors_” and the “_internal_”—by which Mr. Spencer explains it, and have followed it, under both aspects, from the earliest beginnings of progress to the dawn and development of civilisation, such as history knows it. Our account of Mr. Spencer’s theory of the ascent of man and society is necessarily very incomplete; but the various conclusions mentioned in it may be said to be exhaustively typical of the conclusions of social science as Mr. Spencer conceives of it. And now let us consider what the nature of those conclusions is. We shall find that they are, one and all of them, conclusions with regard to aggregates. All the phenomena with which they deal are phenomena not of individuals, not of different classes, but of masses of men, communities, races, nations, {40} the units of which are regarded as being virtually so similar, that what is true of one is virtually true of all. This similarity certainly is not imputed to all mankind. Men are recognised as having been different in one epoch from what they become in another, and one race and the inhabitants of one climate as being different from other men differently born and circumstanced. The primitive millions who could hardly walk upright, and whose sexual relations resembled those of the animals, are distinguished from their erect successors who married and lived in families; and the strong and energetic races are distinguished from their weaker contemporaries. But each of these aggregates is regarded as a unit in itself. The conquering race which has grown vigorous in dry regions, and the inferior race enslaved by it, which has lost its strength in moist regions, are contrasted sharply with each other; but neither is made the subject of any internal division, nor treated as though the units composing it were not virtually similar. Mr. Spencer of course admits (for this is one of the fundamental parts of his philosophy) that these wholes, these aggregates, progress through a constant differentiation of their parts, different functions being performed by an increasing number of groups; but the units who compose these groups, and whom he calls the “_internal factors_,” are regarded by him as being congenitally each a counterpart of the others; and their different functions and their different acquired aptitudes are {41} regarded as the result of different external circumstances which press into different moulds one and the same material. Thus when the single group from which the nation originally springs undergoes, as it becomes more numerous, what Mr. Spencer calls the process of “fission,” and spreads itself in search of food over an ever-extending area, new groups separate not because they have different appetites, but because, having the same appetites, they must satisfy them in different places by the exercise of the same faculties. Division of labour, as we have seen,