Duelling with the Past: Medieval Authors and the Problem of the Christian Era (c. 990-1135) (review)

The dating of the Christian Era was established in the West through the work of Dionysius Exiguus in the sixth century and the popularisation of his Alexandrian Easter calculations in the eighth and ninth centuries. Yet as early as 725 the Venerable Bede, one of Dionysius' leading promoters, made an 'ironic' comment about the inaccuracy of Dionysius' dating of the Incarnation, and between the tenth and twelfth centuries the reckoning came under outright attack in a series of treatises. Peter Verbist's book is a systematic and challenging study of this debate.

Each chapter is dedicated to one of eight writers who challenged Dionysius' work, including such prominent figures as Abbo of Fleury (d. 1004) and Sigebert of Gembloux (d. 1112). After a brief background to the authors, chapters typically explain the importance of the manuscript traditions of their work, then provide a detailed commentary of it, before rounding off with notes on how this work influenced subsequent writers and how it contributed to a growing sense of intellectual autonomy in the period. In the process, Verbist is able to overturn the traditional views of many works, showing for example the logic of the little-studied tapestry of biblical and chronological extracts which form the bulk of Marianus Scottus' late eleventh-century chronicle.

The problems posed by Dionysius' work, and the solutions proposed in the High Middle Ages, are far from simple. On the whole, everything stemmed from calculations of Easter. Traditions based on the Gospels held that Christ was crucified the day after the full moon of the Jewish Passover on a Thursday and was resurrected on a Sunday. Latin traditions gave the date for this Sunday as 27 March, but Greek traditions preferred 25 March. The problem was that Dionysius' Easter tables, projected back to the first decades of the millennium, did not identify the right combination of lunar and weekday data in any of the years AD in which tradition suggested Christ had died (AD 32, 33 or 34).

Strategies for addressing this problem varied wildly, which for Verbist is part of their charm. Herigar of Lobbes (d. 1007), for example, recalibrated the year AD by adopting the tradition by which the Greeks had dated the incarnation eight years later in AD 9, partly because AD 42 was a better - but not perfect - fit for the Gospel data. Most of the computists here, however, found different ways to defend the Latin tradition, placing the Passion in AD 12 with the Incarnation in either 21 BC (Abbo and Sigebert) or 22 BC (Marianus, Hezelo and an anonymous author of Limoges). Some did this on the basis of recalculating the age of the world relative to luni-solar cycles; Marianus, for example, put forward an argument that the year of Creation was the 54th year of the cyclical 532-year luni-solar cycle, and that therefore Christ had risen in AM 4,216, the thirteenth year of such a cycle. As this may suggest, the route through these arguments is far from simple, but Verbist's approach is direct and comprehensible throughout.

On less certain ground is Verbist's argument that this debate ties in with the 'discovery of the individual' in the High Middle Ages. What this means in practical terms is that people were prepared to use reason over authority, effectively inaugurating a period of 'intellectual autonomy'. There are a number of problems here. For a start, reason often played a significant role in innovative thought before Abbo of Fleury; one need only consider the works of the Irishmen Dicuil, Dungal or John Scottus Eriugena in the ninth century, let alone Bede, Alcuin, Isidore of Seville and others who wrote even earlier. It is not readily apparent that the computists discussed here really were more 'individualistic' in their intellectual life (or any other way) than...