For the last two centuries, most historians have considered Beowulf either a work of Germanic prehistory or the early Anglo-Saxon period. Most critics of the poem would not even recognize the possibility that the poem post-dated the Viking invasions of the ninth century AD. As the eminent Dorothy Whitelock put it, why would an English poet praise the very Danes who were ravaging his homeland? This has all changed in the last thirty or so years, as will be seen.
The story Beowulf survives in only a single manuscript which was almost destroyed before being copied! This manuscript is now stored in the British Library and bears the name Cotton Vitellius A.XV. Unfortunately, the fire did damage one of the edges of the manuscript, which began to flake away. At some point after the fire, but before the manuscript reached its maximum extent of deterioration, the Icelandic scholar Thorkelin had two copies made by hand. These proved invaluable in trying to reconstruct the missing text after the manuscript was finally stabilized in the mid-nineteenth century. Paleographers have almost universally assigned the copying of Beowulf to this manuscript to approximately 975 - 1025 AD.
Thorkelin was the first to attempt to date the poem - he argued that it emerged during the fourth or fifth century AD! His contemporaries quickly provided evidence to overturn this conclusion - the key piece of evidence emerging from N.F.S. Grundtvig, who noted that the death of King Hygelac in Beowulf, while raiding Frisia, was essentially the same as that of King Choloilaichus described by Gregory of Tours. This entry in Gregory's history dated to the early 500s, establishing a good terminus ante quem of the mid 500s for the creation of the poem. Another critic, P.F. Muller established what was to be the long-standing terminus post quem with his argument that it could not date to the Viking Age - why would the Anglo-Saxons of that period create a poem that, like Beowulf, praises the Danes who were ravaging their land? This was the last major development to the dating for some time; while some scholars argued in the mid-nineteenth century that the words 'mere wio ingas' in the poem referred to the Merovingians (thus giving a date for the poem predating the fall of that dynasty), the manuscript at that point is unclear and the words could actually be 'mere wic ingas', which means sea raiders, an equally apt term taking into account the context.
While some strides were made in the study of Beowulf in the twentieth century, particularly by the likes of Klaeber, Tolkien and Whitelock, the overall assessment of the date remained the same. The only scholar who suggested otherwise, Schucking, was quickly drowned out. This all changed in the 1970s and early 1980s when a group of scholars brought up very good arguments for the creation of Beowulf in that forbidden age, the Viking Age.
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