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.