BARONIUS, JUSTUS. — Protestant convert, born at Xanten (Silesia) circa 1570; the year and place of his death remain unknown. Educated in a rigorous Calvinism, but shaken by the dissensions among the various sects and by the hostility employed in the struggle against the Roman Church, he took to reading the Catholic Bible and the commentaries of the Fathers, especially those of St. Augustine and St. Cyprian, and became convinced that the Church of Rome had in no way departed in doctrine from the primitive Church: the most specious objection current in the 17th century, directed by Protestants against Catholics. Having come to Rome to investigate these questions more deeply, he was well received by Clement VIII and especially by Cardinal C. Baronio, whose works ultimately confirmed him in the truth. Thus, having returned to his homeland, he wrote to the same Pope of his impending conversion, and the Pope replied (17 January 1601), encouraging him to take the momentous step. The conversion took place in 1601; from then on he also began to call himself Giusto Baronio, in gratitude to the cardinal. Almost nothing is known of his subsequent life; it is merely recorded that he received a doctorate in theology at the University of Siena and in law at that of Perugia, then returned to Germany to study at the University of Heidelberg. Later withdrawing to Mainz, he devoted himself to the conversion of his former coreligionists.
He wrote: Justi Calvini Veterocastrensis pro sacrosanta catholica Romana Ecclesia, proque sua ad eam transmigrazione Apologia (Mainz 1601; 2nd ed. Heidelberg 1756); De latitudine Ecclesiae Dei et moderata coercitione haereticorum (ibid. 1601); Epistolarum Catholicorum liber unus (ibid. 1601; 2nd ed. Mainz 1756); Praescriptionum adversus haereticos perpetuarum ex ss. orthodoxis, patissimum Patribus Tract. IV (ibid. 1602; 2nd ed. ibid. 1756).
