Marie Alphonse Ratisbonne, an anti-Catholic Jew, befriended a baron in Rome and began wearing the [Miraculous Medal](/places/fr-paris-chapel-of-our-lady-of-the-miraculous-medal) as a simple test. On January 20, 1842, after entering the church of Sant'Andrea delle Fratte, Ratisbonne experienced a vision of the Blessed Virgin Mary. He converted to Catholicism, joined the priesthood, and began a ministry for the conversion of Jews.