A 7th-cent. heresy confessing only one will in Christ. Under the auspices of the Emp. Heraclius a formula seemingly acceptable to both Monophysites and Chalcedonians was produced in 624; it asserted two natures in Christ but only one mode of activity or ‘energy’. When Sergius, Patr. of Constantinople, wrote to Honorius c.634, the Pope in his reply used the unfortunate expression ‘one will’ in Christ, which then replaced the ‘one energy’. It was taken up in the ‘Ecthesis’, issued by Heraclius in 638. This forbade the mention of one or two energies and admitted only one will. It was accepted by two Councils at Constantinople but rejected by successive Popes. The controversy was finally settled in 681 when the Third Council of Constantinople proclaimed the existence of two wills in Christ, Divine and human, to be the orthodox faith.