The Type of Constans is an imperial edict released by Byzantine Emperor Constans II in 648 in an attempt to defuse the confusion and arguments over the Christological doctrine of Monotheletism.
Emperor Constans’ grandfather Heraclius had spent the last few years of his life attempting to find a compromise theological position between the Monophysites and the Chalcedonians over their debates about whether Jesus Christ had one nature or two separate natures. What he promoted via his Ecthesis was a doctrine which declared that Jesus, whilst he possessed two distinct natures, had only one will.
This approach seemed to be an acceptable compromise, and it secured widespread support throughout the east. Pope Honorius I and the four Patriarch of the East – Constantinople, Alexandria, Antioch and Jerusalem - all gave their approval to the doctrine referred to as Monothelitism, and so it looked as if Heraclius would finally heal the divisions in the church.
Unfortunately the next Popes at Rome raised a complaint. During that same year of 638, Pope Honorius I too had died. His successor Pope Severinus condemned the Ecthesis outright, and so was forbidden his seat until 640. His successor Pope John IV also rejected the doctrine completely, leading to a major schism between the eastern and western halves of the Catholic Church. When news reach Heraclius of the Pope’s condemnation, he was already old and ill, and the news only hastened his death, declaring with his dying breath that the controversy was all due to Sergius, and that the Patriarch had pressured him to give his unwilling approval to the Ecthesis.