Adam scriveyn, if ever it thee bifalle
Boece or Troylus for to wryten newe,
Under thy long lokkes thou most have the scalle,
But after my makynge thow wryte more trewe;
So ofte adaye I mot thy werk renewe,
It to correcte and eke to rubbe and scrape,
And al is thorugh thy negligence and rape.
Chaucer's Wordes Unto Adam, His Owne Scriveyn
Handwritten texts are subject to a number of errors and inconsistencies. We will first describe some common errors you should be aware of, and briefly outline the ways in which this has affected modern studies of medieval texts.
Scribal Error and Emendation
A scribe might omit a word or write the wrong word when copying a manuscript. Scribes would sometimes inadvertently skip a line, an error known as "eyeskip." Frequently, either the scribe or another reader of the manuscript corrects the error. In the following example, the scribe himself has added a word he omitted above the text:
If a scribe's error was too big to correct with an insertion, he might erase the text by scraping a thin layer of parchment away, and write over the erasure. The purple boxes show where erasures have occurred.
Degredation and Loss of Text
Many medieval texts do not survive in complete versions. Partial or complete loss of a text can be caused by a number of factors. Manuscripts are fragile, and can degrade over time if not stored and handled correctly. (Of course, the manuscript below was damaged before it came to the Houghton!)
Sometimes single leaves or folios of another text were used in the bindings of later books. The dark edges of the leaf below show where it was glued into another book's binding.
Vandalism can be a problem, especially with elaborate, highly decorated manuscripts. When images from medieval illuminated manuscripts became collector's items, they were often cut out of books, taking the text they were attached to with them.
Mouvance and Variance
Different versions of a text frequently circulated in the Middle Ages, and not all scribes had access to the same exemplar when they copied a text. For much of the nineteenth and twentieth centuries, editing medieval texts meant studying the versions of a text to determine the one closest to the original, and demoting any alternate readings to "variant" status. Editors were supposed to create, from the body of mauscript evidence, a singular text that bore the most resemblance to the original author's intention.
In 1972, the French structuralist Paul Zumthor made the case for what he called "mouvance" as an approach to editing and thinking about medieval texts (Essai de poétique médiévale 1972; Towards a Medieval Poetics). For many medieval texts, especially those in the vernacular, attempts to find the "original" text obfuscate the actual mode of circulation of those texts. Texts were adapted and modified at will, and the intention of the original author did not have the same weight with medieval audiences that it does with modern ones. Extending Zumthor's work, Bernard Cerquiglini published Eloge de la variante (In Praise of the Variant) in 1989, in which he makes the case for embracing the variant versions of medieval texts.
For an excellent, in-depth introduction to mouvance and variance, see Bella Millett's website.