The Origins of the Gospel of Thomas

Scholars date the Gospel of Thomas that we have from Nagamadi to around the mid-4th century. The original writings would obviously date before that, but how far back is the question? So it's earlier than 200 or 250 AD. That puts it pretty early in the development of the early Christian Church. But oddly enough, there seems to have been a desire among those early Church Fathers to only have four.