And even in its noblest period the Celtic Church seems to have had but little power beyond the walls of its own colleges.  The whole history of Celtic Ireland, as we learn from the annalists, was one miserable succession of tribal wars, murders and plunderings.  Of course it may be said with perfect truth that the annals of other countries at the time tell much the same story.  But there is this difference between them:  wild and barbarous though the wars of other countries were, they were at any rate the slow and painful working up towards a higher civilization; the country became consolidated under the most powerful chief; in time peace was enforced, agriculture improved, and towns grew up.  The tribal raids of Celtic Ireland, however, were merely for plunder and destruction.  From such conflicts no higher state of society could possibly be evolved.  The Irish Celts built no cities, promoted no agriculture, and never coalesced so as to form even the nucleus of a united kingdom.

It was about the end of the eighth century that the first foreign influence was brought to bear on Celtic Ireland.  The Danish invasion began.  Heathen though the Danes were, they brought some ideas of settled government and the germs of national progress.  They founded cities, such as Dublin, Waterford and Limerick.  And when they, like their fellow-countrymen in England, accepted Christianity, they established bishoprics in the new towns, but took care that they should be wholly independent of the Celtic tribal episcopate; they looked to Canterbury and Rome.

Much has been written and sung about the fame of Brian Boroo.  No doubt he was in some ways a great man; and it seemed for a time that he might do for Ireland something like what Alfred the Great had done for England and Kenneth MacAlpine had done for Scotland—­might consolidate the country into one kingdom.  But the story of his life is a striking commentary on the wretchedness of the period.  Forming an alliance with some of the Danes he succeeded in crushing the chiefs of several rival Celtic tribes; then in turn he attacked his former allies, and beat them at the battle of Clontarf in the year 1014, though they were aided by other Celtic tribes who hated Brian and his schemes even more than they hated the foreigners.  Important though this battle was, its effect has been much exaggerated and misunderstood.  It certainly did not bring the Danish power in Ireland to an end; Dublin was a flourishing Danish colony long afterwards—­in fact it was thirty years after the battle that the Danish king of Dublin founded the Bishopric.

But Brian was slain in the moment of victory.  The soldiers of his army murdered his only surviving son, and began fighting amongst themselves.  Brian’s dream of a united Ireland came to an end, and the country relapsed into chaos.  If the immediate result of the battle was a victory of Celt over Dane, the lasting effect was a triumph of anarchy over order.  It was on the Celtic people that the ruin fell; and the state of things for the next two centuries was if possible worse than it had ever been before.