A palimpsest is a manuscript on which an earlier text has been effaced and the vellum or parchment reused for another. It was a common practice, particularly in medieval ecclesiastical circles, to rub out an earlier piece of writing by means of washing or scraping the manuscript, in order to prepare it for a new text. The motive for making palimpsests seems to have been largely economic--reusing parchment was cheaper than preparing new skin. Another motive may have been directed by the desire of Church officials to "convert" pagan Greek script by overlaying it with the word of God. Modern historians, usually more interested in older writings, have employed infra-red and digital enhancement techniques to recover the erased text, often with remarkable results.
Among the many important palimpsests, the most notable is the Codex Ephraemi Rescriptus of which only 209 leaves have survived. Over the original fifth century text of the Bible, is written the twelfth century sermons of St. Ephrem.
For poststructuralist literary critics, the palimpsest provides a model for the function of writing. Like Freud's discussion of The Mystic Writing Pad, the palimpsest foregrounds the fact that all writing takes place in the presence of other writings--that it is not people who "speak" language, but language which "speaks" people. Palimpsests subvert the concept of the author as the sole originary source of her work, and thus defer the "meaning" of a work down an endless chain of signification.