Those who find that the Church uses highly complicated theological words to define her dogmas might not know much about the events that led to those terms. Passionate and often violent councils led to the definitions of the articles of the Catholic faith. Many reasons led to those councils and there were not always religious but often political.
The Church having asserted two natures in Christ (human and divine) in its first five ecumenical councils, one would obviously have expected the discussion to go further, especially trying to understand how both natures work in one person. The Church had been divided, many churches remaining monophysites. The main cause was of course the disagreement with the doctrine of two natures in Christ but also political issues. It had become obvious that the Roman Empire was losing territories in the East. That is why Sergius, Patriarch of Constantinople, with the approval of Emperor Heraclius I, introduced monothelitism in order to reunify the Church. Monothelitism affirmed the two natures of Christ but also professed one will (thelema in Greek) and one activity (or operation). Although monothelitism succeeded to bring a few monophysites back to the Church, it was rejected by many theologians, including Sophronius of Jerusalem. It was unthinkable to them to say that the divine and human natures of Christ had a same activity. Sergius, convinced by that approach, abandoned the idea of one activity and expressed that by promulgating a decree, Psephos, which forbade all Christians to mention ‘the number’ of Jesus’s activities.
Honorius the First accepts the Psephosbut keeps the idea of one will in Christ and writes it in the Ecthesis in 638, confirming the Psephos and stressed his belief in a unique activity of Christ. Much later, in 648, Constans II abolishes the Ecthesis and promulgates the Typus. He intended to stop the debate but carries on being a monothelite quietly. In the end, in 678 Constantin IV calls for an Ecumenical Council to put an end to a strong division between the churches in the East and those in the West.
The Council lasted for two years (680-681) having taken two more years to start after it had been summoned. Papal legates and bishops gathered at Constantinople and studied the Holy Scripture and the texts of the fathers of the Church, trying to understand the whole question of will and activity in Christ. The Council fathers adopted the theory that affirmed that there are two wills and two activities in Christ. Among them was the Patriarch of Constantinople. In the last paragraphs of the Acts, one can read: “And we proclaim equally two natural volitions or wills in him and two natural principles of action which undergo no division, no change, no partition, no confusion, in accordance with the teaching of the holy fathers”. Their greatest opponent became Macarius of Antioch who was later anathematised together with all those who previously had held the monothelite view. Pope Honorius the First was also condemned for not having condemned but supported monothelitism. Although Agatho was Pope when the Council convened, at its end Pope Leo II had succeeded him and it was to him that the council fathers sent a letter for the confirmation of the Acts.
The Council of Constantinople III might be the one that could confuse us very much as it condemned a thought that intended to reunify the divided Church. But at the same time, one should understand the need of a sound doctrine. And, although the influence of politics in the Church's vital decrees cannot be denied, one could hardly also reject the good will and the honesty of the Councils’ fathers who kept the true doctrine in those councils even when they were not the most powerful or influential. It would thus be unchristian to doubt the work of the Holy Spirit in those councils.