In the historical process by which our knowledge develops, new ideas and new experiences tend very naturally to define themselves by reference to the old. It is not merely that an original thinker must express his originality in terms of old modes of language and thought (which is true and important), but that the new idea, the new experience, being vague and indistinctly grasped, is apt to coin for its expression and propagation phrases in which the emphasis falls upon the difference or variation from what is familiar and concretely understood. In the history of practical developments like that of the theory of political organization this factor is both evident and momentous. In the transition to modern democracy, for example, the familiar distinction between the Sovereign and Subjects dictates the form in which the old order is challenged.