_Castillo_ (Fray Ferdinand del), a Dominican, and one of the most illustrious men of his order. He was implicated in the proceedings against the Lutherans at Valladolid in the year 1559. Fray Dominic de Roxas, Pedro Cazalla, and Don Carlos de Seso, wishing to prove that their opinions on _justification_ were orthodox, declared that they were the same as those of Fray Ferdinand del Castillo, who was universally acknowledged to be eminent for virtue and wisdom; he had been a member of the College of St. Gregory at Valladolid; afterwards professor of philosophy and theology at Grenada: he was at this time a preacher of great eminence at Madrid. The three witnesses ratified their declarations on the 3rd, 4th, and 5th of October, 1559; they were to be burnt on the 8th of the same month. Fortunately for Fray Ferdinand, the three witnesses had not positively asserted that he had maintained the doctrine of _justification_ in the manner that they did, or in the same sense, but that he had expressed himself in such a manner that it might be supposed. Fray Ferdinand was ordered to repair to Valladolid, where he was confined in the College of St. Gregory, and was summoned to appear before the tribunal. He cleared himself from the charges brought against him, and even obtained a certificate of his acquittal, that his honour and reputation might not be affected. He returned to Madrid, where he was made a prior, and was afterwards sent to Medina with the same dignity; lastly he was appointed preacher to Philip II. This prince often consulted him on difficult affairs, and appointed him to accompany the Duke of Ossuna in his embassy to Lisbon. Castillo was one of those who took the greatest part in inducing the Cardinal King, Don Henry, to call Philip II. to succeed him on the throne of Portugal, and he was subsequently made preceptor to the infant Don Ferdinand. He wrote the history of the order of St. Dominic, a work which is much esteemed by the learned of the present day. Castillo died on the 29th of March, 1593: his life had been a model of austerity, and he fasted on bread and water three times a week.