Muirchu aspired to do for Patrick what his father had done for Brigit. But in venturing into what he calls the “deep and perilous sea of sacred story,” he may have been helped by Aed. From the lemma[300] which is found at the end of the Table of Contents to Book I., one might think that Aed has even more claim to be considered the author than Muirchu. Haec ... Muirchu ... dictante Aiduo ... conscripsit. Taken by itself, this might almost suggest that Muirchu’s share in the work was little more than that of a scribe. But such an inference is completely contradicted by the dedicatory preface, in which Muirchu takes upon himself the whole responsibility, though he acknowledges that he had undertaken the work in obedience to a wish of Aed.[301] If, then, the lemma has any good authority,—it may be doubted whether it is due to the author himself,[302]—we must interpret it to mean that Aed furnished Muirchu with some of the material. But it is possible that the note has no good authority, and merely expresses the misconception of a copyist.
Muirchu used written sources. He refers to them in his Preface in the phrase incertis auctoribus, which seems rather to imply that the documents were anonymous than that he was sceptical about their statements. In regard to the character of the sources, it is important to observe that there is a strongly marked contrast between the early portion of the biography up to Patrick’s arrival in Ireland and the rest of the book. The early portion is free from the mythical element; whereas the narrative of Patrick’s work in Ireland is characterised by its legendary setting. These two parts must therefore be carefully distinguished.
In the first part, the best of all authorities, the Confession, is followed (though not without errors in interpretation[303]) so far as it goes; then another source succeeds, dealing with Patrick’s studies on the Continent and his ordination, and including a notice of Palladius. It seems, however, not unlikely that for Muirchu these two sources may have been one; that he may not have used the Confession itself, but a document in which the Confession and the other source had been already condensed. In any case, that other source is marked by the absence of mythical elements and stamps itself as dependent on early and credible records.[304] Nor are other possible traces of this source entirely lacking. It may well be that it was also utilised by the author of the liber apud Ultanum which was consulted by Tírechán.
But when Muirchu’s story passes to Ireland it assumes a different complexion. We enter a world beset by legends. But here too Muirchu used written sources. A legendary narrative had been shaped and written down before his time. The evidence that he used written material here is as follows:—
(1) He refers to writings himself (295₁₆): miracula tanta quae alibi scripta sunt et quae ore fideli mundus celebrat. This seems to imply some stories that were known to him only by oral tradition.
(2) The accounts given by Muirchu and Tírechán of the destruction of the magician who was shot into the air depend on a common written source;[305] and their notices of the angel’s footsteps at Scirte point in the same direction.[306] A comparison of these passages suggests that they are independent translations of a common Irish original.
(3) I have shown[307] that the Lives which are known as Vita Secunda and Vita Quarta depend on a document (W), whose compiler probably used not only Muirchu but Muirchu’s source, which must have been written in Irish.
(4) This conclusion is confirmed by the evidence which I collected in a paper on “Sources of the Early Patrician Documents” (Eng. Hist. Review, July 1904). It is there shown that (a) the prophecy of the magicians (p. 274), and (b) the description of MacCuill’s character (p. 286) reproduce Irish poetical sources. The proof lies in the tabular (columnar) arrangement of these passages in the Liber Armachanus, combined with their rhythmic and assonant character. In that article I also pointed out that the Irish material used by Muirchu began with the account of Patrick’s ordination (if not at an earlier point), the proof being the form Amathorege for Amator of Auxerre. “Muirchu’s Amatorege represents Amathorig and betrays that his source was in Irish.” (On the form compare Zimmer, Nennius Vindicatus, p. 123 note).
The question arises whether part of the written material used by Muirchu, under Aed’s guidance, originated at Sletty (Slébte). There is nothing decisive on this point in the text of Muirchu; for the notice of Fíacc’s presence at Tara may have been inserted by him, from Sletty tradition, in a narrative which did not otherwise depend on Sletty tradition. That this was really the case seems to me to be shown by the fact that (as mentioned above) Tírechán used the same source as Muirchu for an incident in the Tara episode. This fact makes it difficult to suppose that Muirchu’s account of that episode was based on Sletty tradition derived from Fíacc. The legend naturally arose in the regions of Tara and Slane.