In the year 1101, a synod was convened at Cashel by Muirchertach Ua Briain in his capacity as king of Ireland. Although many people are reported as attending, both cleric and lay, the only names we have, apart from that of Ua Briain, are his brother Diarmait and bishop Mael-Muire Ua Dunain. According to one source, Ua Dunain presided over the synod as papal legate; however, doubt has been cast upon the veracity of that claim. Unusually for a synod of this period, its decrees (or at least some of them) have survived; they are found in an Ua Briain genealogy and are believed to be genuine.
There is, however, a dispute over their interpretation. Some would see them reflecting the papal reforms then taking place elsewhere in the church. For example, the first decree is about aithlafch or aithchleirig (often translated as "ex-laymen," "ex-clerics," but also "laymen or clerics who are now penitents"); some historians translate this decree in a way that would suggest that they are being prohibited from purchasing a church. Because of this they see it as a prohibition on simony, a vice that the reform papacy of the time was very keen to stamp out, although they are unable to explain why it applies to the particular category of people in question. Interpreted differently, the decree is seen as a reaffirmation of a long-standing church rule that prohibited such people from taking possession of a church; it is thus a conservative rather than a reforming decree. Similar interpretations could be applied to another decree that prohibits laymen from becoming airchinnig (heads of ecclesiastical establishments). While expressing puzzlement as to why the prohibition is limited to the office of airchinnech, the decree is nevertheless seen to be particularly Gregorian in character. This is because popes and their legates were, around that time, busy on the continent seeking to free the church from the control of lay princes. This interpretation, however, assumes that the office of airchinnech had been taken over by laymen and that the synodsmen were now declaring the practice illegal. However, against this it is argued that the laymen who had taken over the office were in fact clerics, but without ecclesiastical orders, and that the church always forbade laymen from holding the office. The decree merely re-affirms this and is not therefore a reform.
Finally, there is the decree that defines what relationships are considered to be incestuous. Although this is accepted as being very limited in its scope, it is nevertheless seen to be an effort made to address perceived irregularities in Irish marriage practices. There had been many complaints, especially from non-Irish people, about these around the time of the synod. However, it can be argued that many of the foreign complaints were based upon the fact that there was a substantial difference between Irish and mainstream church laws on what was considered to be incestuous. Irish laws, it is argued, were based upon the Mosaic laws, and marriage was allowed between first cousins. Laws in the rest of the church at that time prohibited marriage between people who were related up to the seventh degree of relationship. The decree passed at Cashel confirms existing Irish law and is therefore a restatement of that, rather than being an effort to bring Irish laws into line with those that prevailed in the rest of the church.
This synod is seen as a reforming synod by virtue of the decrees it passed by those who interpret them as reforming decrees. However, there is another event that occurred at the synod, by virtue of which it is perhaps more entitled to carry that title. And it is this event in particular that the annalists picked out for mention, referring to it as unprecedented in Irish history: the grant of Cashel, the ancestral seat of the kings of Munster, by Muirchertach Ua Briain, as a gift to the Irish church forever. The significance of this became clear ten years later when Cashel was chosen at the synod of Raith Bressail as the metropolitan see for the southern province in the new church structure planned there. But it was also significant in that it is the first indication we have of Ua Briain’s changed strategy in relation to church reform at the beginning of the twelfth century. Henceforward, he would pursue a course that would see that reform carried out within a purely Irish context only, with no place in it for Canterbury.
