John IV

John was a Dalmatian, the son of a lawyer named Venantius, and archdeacon of Rome when Severinus died in August 640; the exarch Isaac confirmed him without reference to Constantinople, and he was consecrated on 24 December. He moved fast. A Roman synod in January 641 condemned the doctrine that Christ had one will and the Ecthesis that imposed it, and the emperor Heraclius, dying that February, wrote to the pope disowning the edict as the patriarch Sergius's work. To the new emperor, Constantine III, John sent a defense of the dead Honorius: when his predecessor had written of one will he had meant only that Christ's humanity had no sinful impulses contrary to God's will, not that he lacked a human will. It was a generous reading and the one the church would adopt, though the council of 681 did not.

The other business of the reign was his homeland. Dalmatia and Istria had been overrun by Avars and Slavs, and John sent the abbot Martin with money to ransom Christian captives and to bring back the relics of the Dalmatian martyrs from Salona before the ruined city was lost for good. For them he built the oratory of San Venanzio beside the Lateran baptistery, and its mosaic, with the pope and the Dalmatian saints in a row, is still there, one of the few seventh-century mosaics in Rome.

John died on 12 October 642 and was buried in Saint Peter's. His successor, a Greek from Jerusalem, was consecrated within seven weeks, and the Greek turn of the Roman church had begun.