What information is known about the writings not included in the New Testament?
Ragnar Oborn
1) The Gospel of Thomas extant manuscripts are dated to about 350 AD. It is the most famous and controversial writing in the Nag Hammadi texts (found in 1945 in Egypt). The extant manuscript refers to a Greek translation, of which fragments have been found and are dated to 200 AD. Though scholars debate whether the Gospel of Thomas is Q or related to Q, the fact is that we have no extant copies that exist for a hundred years after the apostolic era. In addition the apostolic successors never quote (either in defence or in refutation) of the Gospel of Thomas. This would be strange given the unorthodox doctrine of this gospel. Later church fathers such as Origen and Eusebius (315 AD) refer to it as a 'bizarre' writing. Since church fathers refute it in the 3rd century, but not in the 2nd, and since we have no extant manuscripts of Gospel of Thomas in 1st or 2nd century this is evidence that it was not composed until the 2nd century. In that case it could not have been written by the Biblical Thomas (one of the 12 disciples) since he would have died by then. Thus the writing was not apostolic.
2) Other writings are found in the Nag Hammadi texts include The Gospel of Philip (which exists only from this one extant manuscript). Again it dates from the middle of the 3rd century. Though it bears the name Philip, it is only so because Philip is named in the text, but not as the author. This gospel alludes that perhaps Jesus married Mary Magdalene (though it is not explicitly stated) see wikipedia for further info.
3) The recently famous Gospel of Judas is dated to the 3rd or 4th century. Though it is asserted that it was a copy of an older source, there is no evidence putting it back to the 1st century.
4) The Gospel of Mary is found in only one extant manuscript (Papyrus Berolinensis 8502), and even here the pages 1-6 and 11- 14 are missing. This manuscript dates from the early 5th century. Thus it does not have apostolic, eyewitness evidence supporting it