The thinking of early sociologists was dominated by a conception of man and society seen progressing up definite steps of evolution, leading through ever greater complexity to some final stage of perfection. The general evolutionary model of society is represented by a large number of specific theories. Comte, for example, delineated three great stages through which all societies must go: those of conquest, defense and industry. For each he enunciated a parallel step in the development of thought, which he conceived as progressing from the theological through the metaphysical to arrive ultimately at the perfection of Comte's own Positive Philosophy. While Spencer's scheme of evolution was much less grandiose, he too held that sociology is the study of evolution in its most complex form.

The evolutionary model treated society as if there were an immanence inherent in social development which requires that each stage appear in turn to play its role according to natural law. This conception understandably tempted the promulgators of social philosophies to capture the evolutionary theory and to use it in support of their political positions.

The American sociologist William Graham Sumner, for example, justified the privileges of the advantaged classes over the disadvantaged on the grounds that such differentiation was a law of nature in keeping with the principle of the survival of the fittest. Sumner, who has been labelled a Social Darwinist, used the idea of evolution, as had Spencer, to block efforts at reform and social change, arguing that social evolution must follow its own course, dictated by nature. That is why, he said, it is the greatest folly of which a man can be capable, to sit down with a slate and pencil to plan out a new social world.