Special principles of selection, different in different societies, affect the composition of the élite so that it no longer includes all those persons best fitted for social rule. Weaknesses set in; and, not compensated by a gradual day-by-day circulation, if they go far enough they are corrected sharply by social revolution: that is, by the sudden intrusion into the élite of large numbers of individuals hitherto prevented by the obstacles from finding their natural social level.
