By reason of his great attainments in theology, Scripture, and Semitic languages, he was considered an oracle in his native Dalmatia.
The opening did not take place, however, until 23 July 1431, in the cathedral church, when John preached from the text: "Et angelus testamenti, quem vos vultis.
[3] Having been sent as a legate of the council to Constantinople to urge the reunion of the Eastern and Western Churches, John of Ragusa induced the Emperor John Paleologus and the Patriarch Joseph to send an embassy to the council through the treaty which they made with Pope Eugenius IV was broken by the Greeks.
He returned to Bologna as a member of a deputation, to obtain from Eugenius IV an assurance that the pope would be present at the council.
John's subsequent course has been a subject of dispute: some authors assert that he remained in sympathy with the council, while others insist that he allied himself with Eugenius IV, who made him Bishop of Argos.