In the summer of 451, the Emperor Theodosius II fell off his horse and was fatally injured. History is always being changed by something or other, but here things shifted decisively for the early Church. His sister, the Empress Pulcheria, who had been regent before his reign, took on the role again and married a man called Marcian. She wanted the question which has arisen as part of the Council of Ephesus – that of the nature of the union in Christ – settled. She had been a great supporter of Cyril of Alexandria, vowed herself to perptual virginity (Marcian had to accept that as part of the marriage contract), Pulcheria had a deep veneration for the Theotokos and the continuign disputes within the church over Christological questions were, she thought, divisive and should be solved.

We have seen in this series that whilst previous Councils had settled some of the questions which had arisen – the fact of the Trinity and its Divine unity, the pre-existence of the Word and His equality with the Father, and the equality of the Spirit with the Father and the Son, and the fact that Christ was human and divine – the issue of how to talk about the two natures of Christ had not been pinned down.  The language of Antioch ended up making Him sound like a very special human being; some of the language coming out of Alexandria made Him sound like a demi-God.

It had taken time after Ephesus for Antioch and Alexandria to come back in to communion with each other. In 433 John of Antioch and Cyril of Alexandria had agreed on a ‘Formula of Union’:

We confess, then, our lord Jesus Christ, the only begotten Son of God perfect God and perfect man of a rational soul and a body, begotten before all ages from the Father in his godhead, the same in the last days, for us and for our salvation, born of Mary the virgin, according to his humanity, one and the same consubstantial with the Father in godhead and consubstantial with us in humanity, for a union of two natures took place. Therefore we confess one Christ, one Son, one Lord. According to this understanding of the unconfused union, we confess the holy virgin to be the mother of God because God the Word took flesh and became man and from his very conception united to himself the temple he took from her. As to the evangelical and apostolic expressions about the Lord, we know that theologians treat some in common as of one person and distinguish others as of two natures, and interpret the god-befitting ones in connection with the godhead of Christ and the lowly ones with his humanity.

It affirmed ‘two natures’ but stressed union and spoke of ‘one person’, as well as Mary as Theotokos.

There are those, amongst whom I number myself, who think Cyril realised that he had, in his zeal, gone too far at Ephesus, and that whilst never regretting seeing of Nestorius, was unhappy to have alienated John of Antioch and that whole tradition. At any rate, whatever his motive, Cyril agreed to the formula and, had things remained there, there would have been no need for another Council; but they did not, and after Cyril’s death in 444, matters deteriorated in a serious way. It is to that we turn next.