The Secret Gospel of Mark is a putative non-canonical Christian gospel mentioned exclusively in the Mar Saba letter, a document of disputed authenticity, which describes Secret Mark as an expanded version of the canonical Gospel of Mark with some episodes elucidated, written for an initiated elite.
In 1973, Morton Smith, a professor of ancient history at Columbia University, reported having found a previously unknown letter of Clement of Alexandria in the monastery of Mar Saba on the West Bank transcribed into the endpapers of a 17th-century printed edition of the works of Ignatius of Antioch. The original manuscript was subsequently transferred to another monastery, and the manuscript is believed to be lost. Further research has relied upon photographs and copies, including those made by Smith himself.
The revelation of the letter caused a sensation at the time, but was soon met with accusations of forgery and misrepresentation. Subsequent study, including handwriting analysis of higher quality color photographs of the document, first published in 2000, revealed more possible evidence of forgery, and led scholars such as Craig A. Evans and Emanuel Tov to conclude the work is a hoax, with Smith being the most likely perpetrator. However, while an increasing number of scholars have been convinced by this view, many still maintain that the Mar Saba letter itself is genuine, and debate continues about the authenticity of the letter and the Secret Gospel it describes.
In 1973, Morton Smith published a book on a previously unknown letter of Clement of Alexandria. He stated that, while cataloging documents at the ancient Greek Orthodox monastery of Mar Saba in the summer of 1958, he discovered the text of the letter handwritten into the endpapers of Isaac Vossius' 1646 printed edition of the works of Ignatius of Antioch. It presented a letter of Clement of Alexandria to one Theodore, whom he seeks to warn against a Gospel of Mark falsified by the gnostic sect of Carpocratians. Clement concedes that it gives a 'more spiritual' version of Mark and quotes from it. This letter is consequently referred to as the Mar Saba letter. In his book, Smith published a set of black-and-white photographs of the text. He published a second book for the popular audience in 1974.