The Céli Dé phenomenon has long been taken by scholars to represent what is here (p. 5) termed a ‘retrospective ideal’ that strove to return to what was imagined to be early Irish monastic observance. Westley Follett considers this to be a mistaken view and, to correct it, takes upon himself the daunting task of re-examining the entire corpus of texts that can be attributed to the Céli Dé. Moreover, having reviewed previous scholarly opinion on the subject (pp. 9–24), he prefaces his own examination of these texts by considering the evidence for Irish asceticism in the period that preceded the emergence of the Céli Dé, which is normally dated to c. 750–850 (pp. 24–88). His reading of the writings of such authors as Columbanus, Cummeanus, Cogitosus and Finnian, fails to yield any evidence of a religious ideal that might be returned to, or any traces of a turning away en masse from previous standards of asceticism (p. 87). There being no evidence of an earlier general decline in standards, the Céli Dé can scarcely have presented themselves as reformers, and this opinion is strengthened by Follett's detailed discussion of the teaching of Maél Ruain of Tallaght, as contained mainly in the text known as the ‘Monastery of Tallaght’ (pp. 89–99). This is followed by a survey of all texts attributed to the Céli Dé, which should prove extremely useful to other students of the period (pp. 100–70). Among other important features of the survey is the author's classification of the criteria to be used in identifying Céli Dé texts. In a concluding chapter (pp. 171–215) Follett reassesses Céli Dé identity on the basis of a number of features in their religious observance, singling out for special mention their highly individual devotional activity. A summary of the study (pp. 216–19) is followed by a very helpful catalogue of the texts attributed to the Céli Dé, with each of the thirty-five entries accompanied by a comprehensive bibliography (pp. 220–34).

As in all such works, there are shortcomings. For example, Irish terms or names would have benefited from the adoption of a standard, preferably Middle Irish, spelling. On a more personal note, I should have liked to see more reliance placed on textual evidence in the discussion of the two Tallaght martyrologies. Similarly, the wholehearted adoption of the controversial view that Brittonic ‘Uinniau’ is the correct historical name of the author of the celebrated penitential and other texts has led to a position where this form of the name is also tacitly used to refer to the distribution of dedications to the saint in Ireland. But these are minor reservations in the context of an excellent study.