Council of Chalcedon
He was a convinced adherent of the Council of Chalcedon and refused to sign Emperor Zeno's Henoticon (which glossed over the Council of Chalcedon). Because of this, the Emperor expelled him and recognized the Miaphysite claimant Peter Mongus as the legitimate patriarch on the condition that he would sign the Henoticon. Mongus complied and was recognized by the patriarchs of Antioch and Constantinople.