His conduct towards Gregorio Riuz ought to be recorded. Riuz was denounced for some explanations of doctrine in a sermon; being obliged to appear and defend his doctrine before theologians, he applied to his friend, the White Doctor, who wished to hear his exposition of the principles he intended for his defence, and the solutions he had prepared for the difficulties which he might meet with. When the assembly took place, the Inquisitors commissioned Arias to argue against Riuz, who was much surprised to see him at this conference, and still more so, when he heard him speak in such a manner, that the answers he had prepared were entirely useless. Riuz sunk under this attack, and the doctor Arias was severely reproached for his treachery by the Lutheran doctors, Vargas, Egidius, and Constantine. Arias taught the Lutheran doctrine to some monks of his convent: one of them (Brother Cassiodorus) made so much progress in it, that he converted almost all the monks of the community, so that the monastic exercises were no longer practised. Twelve of these persons being alarmed at this state of things fled to Germany; the rest who remained at Seville, were condemned by the Inquisition. The same fate awaited Garcia d'Arias; the depositions against him continued to multiply, and he was at last arrested. Foreseeing the result of his trial, he made a confession of his faith, and undertook to prove, that the opinions of Luther were founded on the gospel. He persevered in his impenitence, and no Catholic could convert him, because he understood doctrine better than those who disputed with him.