In order to account for this common material, scholars have conjectured a document they call Q (from the German word Quelle, source). This hypothetical document is used to explain the many sayings of Jesus that appear in Matthew and Luke, but not in Mark. In this theory, both Matthew and Luke used two documents, hence the name “two source theory.” Some scholars assume that this document must have existed in one form or another. For example, G. N. Stanton says that “we can be reasonably certain that Q existed as a written document” (650). Yet scholars such as Thomas Edgar vehemently deny its existence. Edgar states that “Q has never been seen nor is there any evidence that such a document ever existed” (147). The recent book Gospel Writing by Francis Watson makes a compelling case for some sort of Sayings Source, but he does not particularly like the implication of a multi-layered Q document sometimes described int he literature.