Monoenergism (Greek: μονοενεργητισμός) was a notion in early medieval Christian theology, representing the belief that Christ had only one "energy" (energeia). The teaching of one energy was propagated during the first half of the seventh century by Patriarch Sergius I of Constantinople but opposition to Dyoenergism would persist until Dyoenergism was espoused as Orthodoxy at the Sixth Ecumenical Council. Ultimately, monoenergism was rejected as heresy, in favour of dyoenergism.