 In 1564 Dávid was elected by the Calvinists as "bishop of the Hungarian churches in Transylvania", and appointed court preacher to John Sigismund, prince of Transylvania.His discussion of the Trinity began (1565) with doubts of the personality of the Holy Ghost.His antagonist in public disputations was the Calvinist leader, Peter Melius (Bishop of Debrecen 1558-1572); his supporter was Biandrata.