Was Sabellius really a Libyan? Examining contemporary sources and ancient historiography on one of the most enigmatic heretics in the history of dogmas, the article shows that the Libyan origin of Sabellius is unlikely, and that it is an exaggeration to claim that Libya was a Sabellian home in the third century. Eusebius of Caesarea is probably guilty of having identified the adversaries of Dionysius of Alexandria located in Ptolemais as disciples of Sabellius, and the testimony of Origen on the theology of the identification between the Father and Christ is too abstract to deduce that this theology was as widely diffused in the East as it has previously been held.

This article further examines the literary relationship between the De Trinitate falsely attributed to Didymus the Blind and the works of Cyril of Alexandria, aside from their common philosophical citations. The highlighted similarities of these two authors cannot be explained by a common source; on the contrary, they indicate a direct dependence of one author upon the other. Their analysis shows that words, turns of phrase and ideas which are typical of Cyril and often occur in his writings are each used only once by Pseudo-Didymus. This evidence weighs heavily in favour of Cyril’s antecedence. In fact, the anonymous author of the De Trinitate has been influenced, in addition to fourth-century doctrinal treatises, by Cyril’s De sancta Trinitate dialogi, an anti-Arian work dating from the 420s. He also assimilated several other Cyrillian features, and was even inspired by Cyril’s anti-Arian Christology in his doctrine on the Holy Spirit. Cyril of Alexandria, therefore, has priority over Pseudo-Didymus, both chronologically and theologically.