from newly published papers at shroud.com
If you are fascinated by historical theory, like I am, read, FROM JERUSALEM TO EDESSA – THE SHROUD AND THE FAMILY OF JESUS:
Semitic name Addai, abbreviation for Adonija, does not derive from a person of the New Testament. It is necessary to wait until Eusebius – secondary source compared to the Doctrina (Illert 2007: 20) – to identify him with Thaddeus, one of the twelve Disciples (Matteo 10,3 / Marco 3,18) (HE I 12,3). According to the Doctrina, Addai came from “Panea, at the springs of Jordan River” (Howard 1981: 42s). The position against the conjecture that this is a reference to the Gospels is supported by the different name used in the Bible. As a matter of facts, it mentions the place as Caesarea Philippi (Marco 8,27 / Matteo 16,13). Because of this detail, Theodor Zahn’s position is still convincing. He presumes that «since it is totally impartial, this should be considered as a trustworthy tradition through the first, or one of the first, preachers of Christian faith in Edessa» (1881: 369). A significant role into the Doctrina is played by James the Brother of the Lord (Howard 1981: 22-25. 34s).
Yet there is a pre-existent source connecting James with Addai. According to the First Apocalypse of James, the Brother of the Lord had instructed Addai. The Gnostic apocryphal text in Coptic language brought to us, that we know also from the recently (re)published Codix Tchacos, contains Jewish-Christian translations and can be dated back to the 3rd century (Brankaer/Bethge 2007: 114-117; 84s). Richard Bauckham assumes that there had been a mission of the Family Members of the Lord towards East (1990: 66-70) and that Addai, before the year 70, had relations withJerusalem. Richard Bauckham also gives the Apocalypse of James for sure (2008: 265). Also M. L. Chaumont considers the Mission of Addai a verified historical fact (1988: 14-16), but, like Adolf von Harnack (1924: 681), he places it in a later period of time, around the year 100.