Ecthesis a proclamation or formula of faith, in the form of an edict, written by Sergius, patriarch of Constantinople, published A.D. 639 by the emperor Heraclius, to put an end to the troubles occasioned by the Eutychian heresy. It prohibited all controversies on the question, Whether in Christ there were one or two operations? though in the same edict the doctrine of one will was plainly inculcated. A considerable number of the Eastern bishops declared their assent to this law, which was also submissively received by Pyrrhus, the new patriarch of Constantinople. In the West the case was quite different. The Roman pontiff, John IV, assembled a council at Rome, A.D. 629, in which the ecthesis was rejected, and the Monothelites were condemned (Mosheim's Ecclesiastes Hist. N.Y. ed. 1:453). A copy of it is given in Harduin, Concilia, 3:791. See also Gieseler, Church History, 1, § 126; Hefele, Conciliengeschichte, 3:154 sq. SEE EUTYCHIANS.