IAJO (LE JAV), CLAUDIO. — Theologian and controversialist, born around 1500 at Mieussy (Savoy), died at Vienna, in Austria, on 6 August 1552. Having obtained at the Sorbonne (1534) the degree of licentiate in arts and having been ordained a priest, he joined the nascent Society of Jesus at Montmartre on 15 August 1535. Going to Italy (1537), he found there St. Ignatius of Loyola, taking part in the first apostolic activities directed by him, especially in Rome and Ferrara: reconciling the inhabitants divided into factions at Bagnorea and Brescia, and reforming morals at Faenza. In 1542 he departed for Germany, where at Speyer, and above all at Regensburg, he distinguished himself as an orator and controversialist, threatened with death by the heretics but respected for his nobility of life and courage. In 1543–44 he worked at Ingolstadt, Dillingen, and Worms; he took part with St. Peter Canisius in the Diet of 1545; that same year Cardinal Ottone von Truchsess sent him as his representative to the Council of Trent, which he followed in its transfer to Bologna and Ferrara (1545–1549).
Meanwhile King Ferdinand of Austria proposed him as bishop of Trieste, but I. declined, and Duke Wilhelm IV of Bavaria requested him from Pope Paul III for the restoration of the University of Ingolstadt. At Vienna he founded the Jesuit College.
The immense success of his work among the Protestants is attributed by his biographers to his distinction and modesty, accompanied by frankness, simplicity, and affability, as well as to his irreproachable conduct and priestly virtues.