At the risk of over-simplifying, I would like to pass along some things I have learned about the Gospel of Thomas (GTh) mainly from April D. DeConick in THE ORIGINAL GOSPEL OF THOMAS IN TRANSLATION (op. cit). She is a brilliant scholar and is, in my opinion, the leader when it comes to this subject.
On pages 19-21 of the above-mentioned book, De Conick does more to clarify what GTh is and where it came from than anyone else has. There is, first of all, the all-important distinction between the Kernel of GTh (which she dates to the mid-first century), and it's accretions. Then, there is the clear evidence for an Aramaic substratum. Most striking of all, to me at least, is the close relationship that she points to between GTh and the Pseudo-Clementine literature.
On Page 20 we read the following:
"This evidence leads me to wonder how sceptical as scholars we should remain regarding Clement's claim found in the Pseudo-Clementines that he was hired by James to follow Peter, listen to his speeched about Jesus' teachings, and record them in books for the Jerusalem mission."
The import of this is that GTh represents pre-Synoptic material that was in Aramaic in its oral stage, and was then translated into Greek and from Greek into Coptic. As DeConick points out, different translation choices were often made, with many of the translation variants being well explainable by the Aramaic substratum.
Clearly, the Gospel of Thomas is an extremely important document.
