The Context and Development of Irish Literature:
History, Poetry, Landscape
 Part One: From Celtic to Christian, Pre-history to the twelfth century, page 3

The earliest Irish poetry comes from this period, and from the hands of the very monks and scribes who were laboriously copying the Classics. Often scribbled in the margins of a scholarly text, these early poems--the oldest vernacular poetry in all European literature (preceding Chaucer by as much as 7 centuries)--are marked by a tension between the Christian, or orthodox, belief, and the pagan, or unorthodox, belief, a tension that will continue in Irish writing all the way into the 21^st century.  Often the monks would rhapsodize about the beauty of the natural world that surrounded them (as in "The Hermit Marban" or "First of summer, lovely sight!"); other poems seek to reconcile the poet to the doctrines of the Christian faith ("Eve am I, great Adam's wife" or "I'm ashamed of my thoughts").  The New Oxford Book of Irish Verse is a rich collection of this ancient Irish poetry in English translation.  For a good range of this monastic poetry, read the four poems below.  Pay particular attention to the clear sense of the loneliness of the monks, their wonder at nature, and their desire to express something of their lives and observations.

Perhaps the most famous poem of this period is "St. Patrick’s Breastplate"[pp.12-14], a passionate and pious religious prayer to Christ for protection.  Again, for all its apparent orthodoxy of intent, the form of the poem is also an ancient pagan form, called the lorica, a charm or prayer invoking the divine to shield the poet from his enemies, from sin, from the devil. Another tension in the poem will recur throughout Irish literature: that between heaven and earth, between the world of God and the world of nature.  The poet invokes the Trinity, the angels, the saints; but then also invokes "the light of the sun / the radiance of the Moon / the splendour of fire / the fierceness of lightning / the swiftness of wind / the depth of sea / the firmness of earth / and the hardness of rock"--all images of nature, all associated with pagan spirituality, as if even the earliest Irish scribes knew that the world of the Christian God could accommodate only a part of the Irish reality--they knew that the older gods still had a place in Irish life.

This is confirmed by the other strand of Irish poetry during this time, roughly 600 to 1200, which is a continued telling of the great myths of the Irish past, such as the poems from The Ulster Cycle which tell the great Irish myth of the Tain bo Cuailnge (The Brown Bull of Cooley, pp.16-21).   Irish mythology is an endlessly fascinating arena, distinct from the Greek and Norse mythologies though of course parallel to them in many ways (hence the Irish hero Cuchulain is similar to Achilles, Finn bears comparison to Agamemnon, etc.). Another strand of Irish myth can be gleaned from Lady Gregory's compilation, Gods and Fighting Men.  The section titled "Oisin and Patrick" treats of  Oisin, a great figure in Irish myth, who left ancient Ireland for Tir na nOg, the land of everlasting youth, and then returned centuries later, during Patrick’s conversion. When he set foot on Irish soil again, Oisin became an old, old man, a living symbol of the weakening of traditional Irish religion in the face of the new god of Patrick. Oisin’s famous debates with Patrick acknowledge Patrick’s superiority and inevitable victory--but argue that the displacement of the traditional nature worship and the code of the warrior hero is a loss to be mourned. (See Lady Gregory's Selected Writings, ed. McDiarmid and Waters, pp.227-246.)