The Third Council of Constantinople, counted as the Sixth Ecumenical Council by the Eastern Orthodox and Catholic Churches, as well by certain other Western Churches, met in 680/681 and condemned monoenergism and monothelitism as heretical and defined Jesus Christ as having two energies and two wills (divine and human).
The Council settled a set of theological controversies that go back to the sixth century but had intensified under the Emperors Heraclius (610–641) and Constans II (641–668). Heraclius had set out to recover much of the part of his Empire lost to the Persians and had attempted to bridge the controversy with Monophysitism, which was particularly strong in Syria and Egypt, by proposing a moderate theological position that had as good support in the tradition as any other. The result was first monoenergism, i.e. that Christ, though existing in two natures, had one energy (divine and human), the second was monothelitism, i.e. that Christ had one will (that is, that there was no opposition in Christ between his human and divine volition). This doctrine was accepted in most of the Byzantine world, but was opposed at Jerusalem and at Rome and started a controversy that persisted even after the loss of the reconquered provinces and the death of Heraclius. When Heraclius' grandson Constans II took the throne, he saw the controversy as threatening the stability of the Empire and attempted to silence discussion, by outlawing speaking either in favour or against the doctrine. Pope Martin I and the monk Maximus, the foremost opponents of monothelitism (which they interpreted as denying a human faculty of will to Christ), held a synod in Rome in 649 that condemned monoenergism and monothelitism. At Constantinople some accused the Pope of supporting revolution, this was regarded as high treason, and Martin and Maximus were accordingly arrested, tried, condemned and sent into exile, where he soon died.
After Constans' son and successor, Constantine IV had overcome the Muslim siege of Constantinople in 678, he immediately set his sights on restoring communion with Rome: he wrote to Pope Donus suggesting a conference on the matter. When the letter reached Rome, Donus had died, but his successor, Pope Agatho, agreed to the Emperor's suggestion and ordered councils held throughout the West so that legates could present the tradition of the Western Church. There was a synod in Milan under Archbishop Mausuetus; another synod was held in 680 at Heathfield over which Theodore, Archbishop of Canterbury presided. Pope Agatho then convened a synod at Rome at Easter 680, with representatives from the regional synods.
Then he sent a delegation to meet the Easterners at Constantinople. The delegates set out bearing two letters, one from Pope Agatho to the Emperor, and the other from the bishops of the Rome synod to those gathered in Constantinople.
In the meantime, Constantine summoned Patriarch George I of Constantinople and all bishops of his jurisdiction of Constantinople to a council. He also summoned Patriarch Macarius of Antioch, a Byzantine appointee permanently resident in Constantinople because of the Muslim occupation of his see.
On 7 November 680, a mere 37 bishops and a number of presbyters convened in the imperial palace, in the domed hall called the Trullus. The Patriarchs of Constantinople and of Antioch participated in person, whereas the patriarchates of Alexandria and Jerusalem were represented by Byzantine appointees (because of the Saracen Muslim conquest there was at this date no patriarch in either of these sees). The Pope and a council he had held in Rome were represented (as was normal at eastern ecumenical councils) by a few priests and bishops. In its opening session, the council assumed the authority of an Ecumenical Council. The Emperor attended and presided over the first eleven sessions, took part in the discussions and returned for the closing session on 16 September 681, attended by 151 bishops.
During the council, a letter by Pope Agatho was read which asserted as the traditional belief of the Church that Christ was of two wills, divine and human. Most of the bishops present accepted the letter, proclaiming that Peter spoke through Agatho, though ironically this council also proclaimed another historical pope as anathema. Macarius of Antioch defended monothelitism but was condemned and deposed, along with his partisans. The council, in keeping with Agatho's letter, defined that Jesus Christ possessed two energies and two wills but that the human will was 'in subjection to his divine and all-powerful will'. The council carefully avoided any mention of Maximus the Confessor, who was still regarded with suspicion. It condemned both monoenergism and monothelitism as heretical and included those who had supported this heresy, including Pope Honorius I and four previous patriarchs of Constantinople. When the council had concluded, the decrees were sent to Rome where they were accepted by Agatho's successor, Pope Leo II.
At some point during the council's proceedings, a Monothelite priest claimed he could raise the dead, thereby proving his faith supreme. He had a corpse brought forth, but after whispering prayers into its ears, could not revive the body.