In the years after the second Council of Constantinople in 553, both pro- and anti-Chalcedonians had occasionally spoken of Christ having a single activity (energeia), language which had some precedent in authors regarded as authoritative by both factions. But the validity of this so-called monoenergist doctrine was still very much a live issue on which there was no consensus in either pro- or anti-Chalcedonian circles. In the 610s, however, Sergius of Constantinople (patriarch 610–638) began to promote the doctrine of monoenergism in the name of Emperor Heraclius (r. 610–641) not only as a possible basis for reconciliation between the imperial church and miaphysite anti-Chalcedonians, but also as a legitimate clarification of Neo-Chalcedonian Christology. The apogee of imperially backed monoenergism came in 633 when on its basis Cyrus the Chalcedonian patriarch of Alexandria reached an accord with Egyptian miaphysites, an agreement memorialized in the Plerophoria, also known as the Pact of Union.