The purpose of Cyril’s attendance at Seleucia was to appeal against his deposition by Acacius, and there is apparently no evidence of his having taken part in the doctrinal discussions, or signed the Creed of Antioch There is, I believe, no extant list of signatures:  “Whether the few Homoüsians and Hilary were among those who signed is not said” (Hefele, Councils, II. p. 264.).  What is certain is that Cyril’s bitterest enemies who refused to sit with him in the Council were Acacius and his Arian allies, who expressly rejected both ὁμοούσιος and ὁμοιούσιος and “altogether denied the Nicene formula and censured the Council, while the others, who were the majority, accepted the whole proceedings of the Council, except that they complained of the word ‘Co-essential,’ as obscure, and so open to suspicion Athan. De Synod. c. 12..”  It thus appears that Cyril’s friends at Seleucia were partly those who approved the word “ Co-essential,” and partly those of whom Athanasius speaks as “brothers, who mean what we mean, and dispute only about the word Ib. c. 41..”  It needed in fact the profound insight of an Athanasius to foresee that in the end that word must triumph over all opposition, and be accepted by the Universal Church as the one true safeguard of the Christian Faith.  Meanwhile it was the standard round which debate, and strife, and hatred, and persecution, were to rage for fifty years with unexampled fury.