This significant literature, the earliest extensive record in any European vernacular north of the Alps, was written by scholars who were educated in the monastic schools of the period. While they composed poetry which was obviously personal, the extent to which other parts of the extant corpus were their own creation or a record of orally transmitted tradition is a question on which modern scholars are not fully agreed. Much of the saga literature, for example the epic Táin Bó Cúailnge (The Cattle-Drive of Cúailnge), purports to represent a pre-Christian society, but monastic writers supplied the narrative structure, and many details of the content may equally be the product of their imaginations. So also it has been demonstrated that even the earliest law texts show ecclesiastical influence. The conclusion that they also preserve elements of an ancient pre- Christian tradition seems irrefutable, but the exact relationship between tradition and innovation in the earliest literary record remains to be determined.

Irish literature of this early period was not without influence on later European literature. The theme of tragic love, as found in the legend of Tristan and Isolde, is thought to derive ultimately from Irish sources, such as the tales of Deirdre and Naoise, Líadan and Cuirithir, and Gráinne and Diarmaid. And tales of fantastic voyages, such as Imram Maíle Dúin (The Voyage of Máel Dúin) and the Latin Navigatio Brendani (The voyage of Brendan), captured the imagination of medieval Europe.