At the heart of the dispute was not the power struggle depicted by Gibbon and others, but the very nature of our salvation. Nestorius’ position was clear:

That God passed through the Virgin Christokos I am taught by the divine Scriptures, but that God was born from her I have not been taught anywhere

Nostorius argued that those who taught that Mary was Theotokos were ‘heretics’. (Russell, p. 34) This he proclaimed from the cathedra in Constantinople; this it was which so concerned Cyril. As neither of his first two letters secured any concessions from Nestorius, and with the latter clearly marshalling the forces of the Empire against him, Cyril needed to gather his own resources. His attempts to garner support from the sister of Theodosius back-fired; but he fared better elsewhere.

In the summer of 430 Cyril sent Pope Celestine a dossier on Nestorius’ teaching, along with a commentary and patristic testimony. The Pope, no theologian, handed the dossier to his archdeacon, Leo (later Pope Leo the Great) and John Cassian, the two most formidable theologians in the West; they advised him that Cyril was correct.   On 11 August 430 a local synod was held in Rome. It condemned the teachings of Nestorius as heretical. Celestine told Cyril of this and appointed him his representative at the synod which it had been announced would take place at Ephesus. Nestorius’ own appeals to Celestine went unanswered. For those who care about such matters, it ought to be noted that both patriarchs appealed to Rome for support.

In November 430 a local synod at Alexandria found Nestorius guilty of heresy. St. Cyril send a third letter to Nestorius containing 12 anathemata which he was required to accept as the price of entering back into communion:

1. If anyone does not confess the Emmanuel to be truly God, and hence the holy virgin to be Mother of God (for she gave birth in the flesh to the Word of God made flesh), let him be anathema.

2. If anyone does not confess that the Word of God the Father was hypostatically united to the flesh so as to be One Christ with his own flesh, that is the same one at once God and man, let him be anathema.

3. If anyone divides the hypostases of the One Christ after the union, connecting them only by a conjunction in terms of honour or dignity or sovereignty, and not rather by a combination in terms of natural union, let him be anathema.

4. If anyone interprets the sayings in the Gospels and apostolic writings, or the things said about Christ by the saints, or the things he says about himself, as referring to two prosopa or hypostases, attributing some of them to a man conceived of as separate from the Word of God, and attributing others (as divine) exclusively to the Word of God the Father, let him be anathema.

5. If anyone should dare to say that Christ was a God-bearing man and not rather that he is truly God as the one natural Son, since the Word became flesh and ‘shared in flesh and blood just like us’ (Heb.2.14), let him be anathema.

6. If anyone says that the Word of God the Father is the God or Lord of Christ, and does not rather confess the same one is at once God and man, since according to the scriptures the Word has become flesh, let him be anathema.

7. If anyone says that Jesus as a man was activated by the Word of God and invested with the glory of the Only Begotten, as being someone different to him, let him be anathema.

8. If anyone should dare to say that the assumed man ought to be worshipped along with God the Word and co-glorified and called ‘God’ as if he were one alongside another (for the continual addition of the phrase ‘along with’ demands this interpretation) and does not rather worship the Emmanuel with a single veneration and render him a single doxology since the Word became flesh, let him be anathema.

9. If anyone says that the One Lord Jesus Christ was glorified by the Spirit, using the power that came through him as if it were foreign to himself, and receiving from him the power to work against unclean spirits and to accomplish divine signs for men, and does not rather say that the Spirit is his very own, through whom he also worked the divine signs, let him be anathema.

10. The divine scripture says that Christ became ‘the high priest and apostle of our confession’ (Heb.3.1) and ‘offered himself for our sake as a fragrant sacrifice to God the Father’ (Eph.5.2). So if anyone says that it was not the very Word of God who became our high priest and apostle when he became flesh and man as we are, but it was someone different to him, a separate man born of a woman; or if anyone says that he made the offering also for himself and not rather for us alone (for he who knew no sin had no need of offerings), let him be anathema.

11. If anyone does not confess that the Lord’s flesh is life-giving and the very-own flesh of the Word of God the Father, but says that it is the flesh of someone else, different to him, and joined to him in terms of dignity, or indeed only having a divine indwelling, rather than being life-giving, as we have said, because it has become the personal flesh of the Word who has the power to bring all things to life, let him be anathema.

12. If anyone does not confess that the Word of God suffered in the flesh, was crucified in the flesh, and tasted death in the flesh, becoming the first-born from the dead, although as God he is life and life-giving, let him be anathema.

This, along with the decision of the Roman synod, was conveyed to Nestorius on 30 November. Only two weeks earlier, on 19 November 430, Theodosius II had invited the bishops to a synod to be held at Pentecost (7 June 431). The scene was set for one of the most controversial of all ecumenical councils, and an occasion which would provide Cyril’s opponents with much ammunition.