Whence the Homoousion? Revisiting the Tertullian– Ossius–Nicaea Thesis

While modern scholars once commonly assumed that Tertullian’s phrase una substantia was introduced to the council of Nicaea by Ossius of Cordoba so as to become in Greek the term homoousios, in recent decades experts have asserted that this thesis has been disproven. Alternative origins of the phrase have been suggested, even though none have offered sufficient or compelling reasons to garner a consensus, and thus the background and development of the Homoousion was lost. A fresh assessment, however, of this scholarly shift can demonstrate that several mistakes were made, and so the case needs to be reopened. Ossius is in fact the most probable candidate for introducing the concept at Nicaea, given the evidence. Furthermore, Tertullian’s popularity throughout the third and fourth centuries can be established with certainty so that he is the most likely source of this concept for western thinkers like Ossius, who knew his works. Even so, it needs to be acknowledged that Tertullian’s una substantia functioned in a very different, if not opposite way, to Nicaea’s usage. In sum, Tertullian’s contribution to Nicaea via Ossius, and his distance from it given his context, can both be acknowledged, and thus a better account of the historical development of the Homoousion can be offered.