This article discusses the history of Ireland from the sociological standpoint. It is in the light of this simplification that the history of Ireland must be viewed; and so viewed, it will like all extreme cases, like all crucial instances, be found peculiarly rich in sociological material. It is, in its earlier history, a nation from its geographical position less affected by the movements of its neighbors or the general course of development than any other. It thus retained to an unusual extent the characteristics of the ancient Aryan civilization, once common to all Europe, and was peculiarly homogeneous in itself, and markedly separate from its neighbors. This distinction was maintained, in spite of one serious breach, the introduction of Christianity-till the first invasion from the island larger, richer, and closer to the centres of Western civilization, which lay between it and the continent of Europe. And if the earlier history of Ireland is of interest as the case of a Western people growing up in comparative isolation, the later history has an even stronger interest. It is that of a people peculiarly homogeneous and distinctive in their civilization exposed to a continuous pressure from a country possessing far greater resources and in some respects much further developed, an era of isolation followed by an era of domination, a civilization of peculiar strength subjected to an external pressure of peculiar intensity and continuance.