How and why do you label an idea as belonging to a particular culture?

I have been looking at a ninth-century collection of materials on history, calendars and the Easter reckoning which highlights the difficulties in answering this question. The collection (Milan, Biblioteca Ambrosiana, H 150 inf) is known as the ‘Bobbio Computus’ [1] because it came to reside in the monastery of Bobbio, founded by the Irishman St Columbanus in northern Italy shortly before his death in 615. The great Bernhard Bischoff believed that the manuscript had been written in North-eastern France, and indeed there are a number of items in the collection which are clearly Frankish. The latest date referred to as the ‘present year’ in the collection is 827/8 but there are other, earlier years given in various sections of the manuscript which show that the compiler(s) had a range of texts available to them.

The texts in the Bobbio Computus illustrate some diverse cultural horizons. For a start, these texts include a number which have a demonstrable Irish pedigree although – and this is important – they are not identified as such in the manuscript. Most are identical or similar to the treatises in the ‘Sirmond group’ assembled in 658 and later known to Bede.

The Frankish material is, in a sense, better marked. There is one passage, based on Gregory of Tours’ Histories IV.51, dating the death of King Sigibert I to 575. (The last sentence, confusingly, has been changed at some point to date the beginning of the reign of Theuderic II of the Visigoths instead of Sigibert’s death). A second note dates the present year to 673, the 16th year of the reign of King Chlothar III in Burgundy.

There are other things going in the manuscript, too. It contains an old Roman 84-year table no one had used for centuries. It also contains some formulae from 810 which seem to respond to a meeting in Charlemagne’s Aachen to discuss calendars in 809.

Culturally, then, the compilation is all over the place. And the only labels consistently used throughout the compilation distinguish between Greek (ie Alexandrian) and Latin approaches to calculating Easter.

There are differences in opinion concerning what this all adds up to. Arno Borst, in 2006, described much of the Bobbio Computus as an Irish composition started in 703 and thereafter built up piecemeal in Frankish territories. His date of 703 (which should actually be 702 – there’s a copying error) comes from a single chapter, known only from this collection, which identifies that as the present year. Why this represents an important moment of composition is not made clear, as there are plenty of other dates in the computus, some earlier and some later, all jumbled together unsystematically. There is nothing about the material, either, which means that it must have been composed in Ireland rather than on the continent – although balance of probability says that it was at least based on materials imported from Ireland or the English kingdoms. Really, we should say that, around 827, whoever compiled the material had an old text from 702 s/he part-copied into their new compilation.

Technicalities, technicalities. They are important. But to return to the labels:

Whether anything in the compilation was Irish, Frankish or even Roman (or Gothic), in the ninth-century manuscript in which it is all found, it is all part of a universal collection of useful knowledge. Our interest in identifying origins and contexts is fine – but it is always striking how quickly ideas can escape from such confines.

[1] The first section of the computus was transcribed – not always accurately – by Muratori, and this material is most accessible in Patrologia Latina vol. 129 as ‘Liber de computo’.