After this brief survey of Celtic mythological remains it may occur to the reader to ask how much of their original significance these still retained when they were first written down by monastic scribes in the seventh century. But unfortunately, since we know so little about the actual content of the teaching imparted in the schools of the filidh and bards at that time or the nature of their commentaries on individual tales, the answer must be inferential and speculative. That some aura of their ancient efficacy still attached to the tales is beyond question, for they are not infrequently accompanied by a statement of special benefits that may be obtained by narrating them or by listening to them attentively: protection against sickness and death, prosperity, numerous progeny, and so on. And as has been pointed out, much the same virtues are ascribed to the traditional stories of India.
In some instances - kingship, royal inauguration, the notion of sovereignty, to take but a few related examples - there is abundant evidence that the symbolism and the function of both myth and ritual were still clearly perceived. It is also significant that so many pagan traditions and cults survived and flourished almost to our own day in consequence of the fact that they were accommodated under the capacious mantle of the Church and thereby acquired a rather spurious seal of respectability. Pagan deities were canonised out of number. Brighid became St Brighid and her cult continued uninterrupted. St Ann has attracted legends of the goddesses Anu and Áine. In several localities the memory remains of three holy sisters who cannot easily be dissociated from the trio of goddesses who figure so often and so prominently in the early mythological legends ... and so on.
This kind of assimilation is not peculiar to the insular Celtic countries, but apart from the fact that it is especially common there, it also reflects a more general tendency of the Christian Church to adapt itself as far as possible to indigenous customs and institutions, a tendency incidentally which had much to do with the remarkably peaceful transition from paganism to Christianity. In part it was a matter of deliberate policy, as when the Christian metropolis of Ard Macha was sited within two miles of Emhain Mhacha, the capital of the Ulaidh, or when monastic foundations were established on the sites of druidic schools or pagan cult-centres. But even more perhaps did it reflect the natural reactions of a clergy who were the creatures of their environment and quite incapable of abandoning the traditions and the patterns of thought which had moulded their own identities and which continued to inform the whole of contemporary society. The Irish Lives of the Saints offer a good illustration of this. Beginning as reasonably sober documents, they gradually deteriorate into a 'literature of fantasy, which under the pretext of honouring the saints has so often obscured their memory'and which so teems with mythological motifs that often the boundary between hagiography and mythology becomes largely notional.
In all the vast range of traditional material handled by the monastic scribes and literati nothing seems to have captured their imagination quite so compeltely as the theme of the voyage to the happy otherword. comparison  between the accounts of the voyage to the otherworld and the complex, elusive ornament of Celtic art. She finds both characterised by the same aversion to rigidity and to barren realism and she sees in the illuminated pages of the Gospel books the artistic reflex of the polymorphic otherworld:
Like the illuminated manuscript the otherworld tale offered an aesthetically appropriate medium for a combination of spiritual quest and vision which had existed before Christianity and which centuries later received, if not its finest, at least its most celebrated expression in the legends of the Grail. But, above all else, what ensured the otherworld tale its unique favour among the monastic poets and storytellers was its evident analogy with the biblical terra repromissionis, in Irish Tír Tairngiri, 'The Land of Promise'. In the earliest of the Voyage tales there is an implicit equation of the two which in several later tales gradually progresses te wards an explicit identification as the overseas journey is transformed into a Christian peregrinatio, without however shedding any of its propensity to the marvellous. The culmination of this particular evolution was the Navigatio Brendani, 'The Voyage of St Brendan', which was written perhaps in the ninth century, was translated in due course into most of the languages of Europe and became Ireland's greatest single contribution to medieval European literature.
The Voyage tales directly affected by this Christian adaptation comprise only a relatively modest segment of the otherworld materials that have survived in Irish, not to speak of the whole range of mythological tradition that existed formerly. But nonetheless they do bring home to one the paradox that the early mythographers from whom we have received the extant tradition had a transcendent and conflicting loyalty, since their spiritual purpose was to eradicate the religious system which gave the mythology its meaning; and clearly this casts a shadow of suspicion upon the integrity of their text. Insular mythology, we have often been reminded, is 'anarchical' and lacks the semblance of a system such as one finds in other Indo-European mythologies, in addition to which it is lamentably short on such items as cosmogony and eschatology. And the conclusion is sometimes drawn that these are primary defects, on  the assumption that they cannot be ascribed to the censorship of Christian monks 'who were ... liberal enough to allow the preservation of episodes much stained with paganism, and features most shocking to the Christian mentality'. In point of fact, however, we can only surmise - perhaps quite erroneously - which details of pagan tradition were most likely to offend the moral sensibility of a seventh or eighth century monastic literatus. On the other hand, we can be tolerably certain as to the kinds of myth that would inevitably have come into collision with the doctrines of his Church; and it goes without saying that they include those particular features in which Celtic religion and mythology are seen to be seriously deficient. There is therefore a strong presumption that these elements, in so far as they were present in the seventh century, were expunged by the monastic redactors because they found them blatantly irreconcilable with some of the principal tenets of Christianity.
That some of these features had formerly been present is, in any case, not an unreasonable assumption. The cult of sacred trees which are evidently replicas of the Cosmic Tree and the 'various cosmographic traditions such as those relating to Tara argue strongly the existence of a cosmology and a cosmogony; the deluge and the plague which annihilated the peoples of Cesair and Partholán as likely as not continue native traditions of a cosmic cataclysm such as may be found in mythologies of beginnings throughout the world, and the manifold legends of the otherworld or land of the dead might very well conceal the debris of an eschatology. There are also many references and residual testimonies which indicate that there must once have been a vast body of ritual which fell into disuse at some stage and was noticed only casually in the written record. Now we know that in pre-Christian Celtic society such matters as these would have fallen within the purview of the druids (of whom Caesar says that they 'are concerned with the worship of the gods, look after public and private sacrifice, and expound religious matters'). At the same time Irish literature leaves us in little doubt that the druids were the unremitting antagonists of the Church in a long-drawn-out ideological struggle which ended in the virtual annihilation of the druidic organisation. It is therefore not unreasonable to suppose that the monastic redactors did in fact suppress elements of druidic teaching and practice which they could not record without seeming to compromise the doctrines of the universal Church. 
Obviously, then, what remains of Irish mythology - to name only the more richly documented of the two insular branches - is not the integral tradition, however archaic it may be in many respects, and one can only surmise how closely it approximates to that expounded by the druids in the fifth century when St Patrick first set foot in Ireland. Any assessment of the mythology which does not take account of this discrepancy but instead assumes the integrity of the written record, runs the risk of misrepresenting the character and scope of the mythology in its pre-Christian form. To say of the insular tradition, as one distinguished scholar has, that 'one searches in vain for traces of those vast conceptions of the origin and final destiny of the world which dominate other Indo-European mythologies', is a pardonable overstatement, but to conclude from this that such conceptions were foreign to the Celts is to presume too much on the evidence.
One is reminded of an Old Irish text which tells of a visit by one of the otherworld people to St Columcille. After a preliminary conversation Columcille took his companion aside out of hearing of the monks who were with him'in order to converse with him and to question him about the heavenly and earthly mysteries. While they were conversing from one hour to the same hour on the next day, Columcille's monks watched them from afar. When the conversation had come to an end, they suddenly beheld the young man vanishing from them. It is not known whither he went. When his monks begged Columcille to let them know something of the conversation, he said to them that he could not tell even one word of what had been told to him, and said that it was proper for men not to be told.' The matter of this little tale is quite apocryphal, but obviously not invented from nothing. The reticence which its author ascribes to Columcille was more probably a reflection of his own experience and outlook. And as for those 'heavenly and earthly mysteries' which were revealed to the saint, one wonders whether they may not indeed have had some bearing upon 'the origin and final destiny of the world'.
[End][Bibliography:] Further reading list