Hypostatic union

The hypostatic union is the doctrine that in Jesus Christ divine and human natures are united in one person, one hypostasis, without either being diminished. Its authoritative formula is that of the Council of Chalcedon in 451, which confessed Christ "acknowledged in two natures, without confusion, without change, without division, without separation", the distinction of the natures not being taken away by the union but the property of each preserved and concurring in one person.

The formula was hammered out against two pressures. Alexandrian theology, above all in Cyril of Alexandria, insisted on the unity of the subject: it is the Word himself who is born, hungers, suffers and dies, and Mary is therefore properly called Theotokos, God-bearer, because what she bore is a person and that person is God. Antiochene theology, in Theodore of Mopsuestia and Nestorius, insisted on the integrity of the two natures and resisted language that attributed suffering or birth to the divine as such. Nestorius' objection to Theotokos precipitated the Council of Ephesus in 431, which deposed him. Eutyches then pushed unity so far as to hold that after the union there was only one nature, and Chalcedon condemned that as well, so that the council defined against both extremes at once.

Chalcedon did not produce agreement. The Oriental Orthodox churches, Coptic, Syriac, Armenian, Ethiopian and Malankara, rejected its formula as conceding too much to a division of natures, and hold the miaphysite position of one incarnate nature of the Word, following Cyril's own preferred language. They reject the label "monophysite" and deny holding that Christ's humanity was absorbed by his divinity. The Church of the East, historically labelled Nestorian, holds two natures and, in its classical formulations, two hypostases in one prosopon, and likewise rejects the label as a misdescription of its faith. These divisions produced separate communions that have persisted for fifteen centuries, and they were entangled from the beginning with imperial politics, with regional rivalry between Alexandria, Antioch and Constantinople, and with the difficulty of translating a Greek technical vocabulary into Syriac, Coptic and Armenian.

Since the 1960s a series of joint declarations has substantially altered the picture. Agreements between the Oriental Orthodox and Eastern Orthodox churches, the common declaration of Pope Paul VI and Pope Shenouda III in 1973, and the Common Christological Declaration signed by Pope John Paul II and Patriarch Mar Dinkha IV of the Assyrian Church of the East in 1994 each state that the churches confess the same faith in Christ in differing formulas, and that the ancient condemnations rested substantially on terminology and circumstance. Most historians accept a good deal of this while noting that genuine differences of emphasis remain, and that agreement at the level of Christology has not by itself restored communion.

Article one's account of Chalcedon in 451 settles how many natures Christ has. It does not settle how many wills or modes of operation he has, and that further question produced its own council, its own condemned position, and its own martyr.

Seventh-century theologians proposed monoenergism, that Christ acts through a single divine-human energy, and then monothelitism, that he has a single will, as compromise formulas intended to win back the Oriental Orthodox churches article one describes without reopening Chalcedon's two-natures settlement itself. Maximus the Confessor argued that a nature without its own will and operation is not a complete nature at all, so that a single will in Christ would mean he did not possess a complete human nature, quietly undoing Chalcedon's own achievement under cover of appearing to defend it. For that position Maximus was tried, had his tongue cut out and his right hand amputated by imperial order in 662, specifically to stop him from preaching or writing further, and died shortly afterward in exile.

The Third Council of Constantinople, meeting in 680 and 681, vindicated Maximus's position after his death, condemning monothelitism and monoenergism and confessing two natural wills and two natural operations in Christ, undivided, unconfused and unopposed to one another, corresponding exactly to the two natures Chalcedon had already defined. The council's formula follows Chalcedon's own logic to a conclusion Chalcedon itself had not made explicit, and it is a clear instance of a settled dogma generating a further, genuinely new dispute rather than closing the subject, decided in the end by a council condemning what an emperor had spent decades trying to impose as a unifying compromise.