under an incapacity for comprehending any reason except this for their holding together in political union. The history of political ideas begins, in fact, with the assumption that kinship in blood is the sole possible ground of community in political functions; nor is there any of those subversions of feeling, which we term emphatically revolutions, so startling and so complete as the change which is accomplished when some other principle—such as that, for instance, of local contiguity—establishes itself for the first time as the basis of common political action. It may be affirmed then of early commonwealths that their citizens considered all the groups in which they claimed membership to be founded on common lineage. What was obviously true of the Family was believed to be true first of the House, next of the Tribe, lastly of the State. And yet we find that along with this belief, or, if we may use the word, this theory, each community preserved records or traditions which distinctly showed that the fundamental assumption was false. Whether we look to the Greek states, or to Rome, or to the Teutonic aristocracies in Ditmarsh which furnished Niebuhr with so many valuable illustrations, or to the Celtic clan associations, or to that strange social organisation of the Sclavonic Russians and Poles which has only lately attracted notice, everywhere we discover traces of passages in their history when men of alien descent were admit-
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