or D'Aquino, Thomas, commonly called St Thomas, the greatest philosopher and theologian of the middle ages, was of noble descent, and nearly allied to several of the royal houses of Europe. He was born, according to the most probable opinion, in the year 1227, at Rocca Siccà, the castle of his father Landulf, Count of Aquino. Having received his elementary education at the monastery of Monte Cassino, he studied for six years at the university of Naples. The rising order of St Dominic numbered at that time many men of eminent energy and talents, zealous for the extension of their brotherhood, and particularly eager to draw into their ranks whatever of youthful genius and enthusiasm came within the range of their influence. The young Aquinas was soon led to choose a profession so congenial to his nature; and in direct opposition to the wishes of his family, embraced at the age of 17 the habit of St Dominic. His mother attempted in vain to rescue her son from the hands of the Dominicans, who first removed him to Rome and then attempted to convey him to Paris. His two brothers, officers in the Aquinas. Tuscan army, were directed to intercept the passage of the travellers, who had proceeded no farther than Acquapendente, when the young friar was suddenly seized while reposing by a wayside fountain, and carried back to Rocca Sicca. Here he was kept for two years in close confinement, while his relatives exhausted vain every argument and temptation which could have moved a less resolute spirit from its steadfastness. He employed his solitude profitably in meditation and study, having procured through his sisters a Bible, the Logic of Aristotle, and the Sentences of Lombard. Having at length succeeded in making his escape, he at once joined the Dominicans at Naples, and was soon after sent to study under Albert the Great, at Cologne. Here his taciturn and meditative deportment excited the contempt of his more loquacious fellow-students, who bestowed on him the title of the Dumb Ox of Sicily. His great teacher discerning better the profound genius of his silent pupil, told them that "When the dumb ox began to bellow, he would fill the world with the sound of his voice."

In 1245, Aquinas followed his master to Paris, returning with him at the end of three years to Cologne. In 1253 he again went to Paris, to fulfil the customary term of three years for obtaining his degree as doctor of theology. His lectures during that time were attended by crowds of enthusiastic scholars. The reception of his degree was obstructed by the contest of his order with the University of Paris, headed by William of St Amour. Both parties were summoned to plead their cause at Rome. Aquinas appeared as the champion of the mendicant orders, and the result of his powerful pleading was the condemnation of his adversary. In October 1257, he received his degree on the same day with his saintly friend Bonaventura.

For three years longer he continued at Paris, assiduous in teaching, preaching, and writing. His relative Louis IX. invited him frequently to the court, and sought his counsel on state affairs. The story of his one day startling the company at the royal table by exclaiming, out of an absorbing fit of meditation, "Conclusum est contra Manichaeos!" is perhaps more generally familiar than his pointed reply to Pope Innocent IV. Aquinas found the Holy Father seated by a table covered with piles of indulgence-money. "You see," said the Pontiff, "the church is no longer in the days when she could say, 'Silver and gold have I none.'" "True, Holy Father," said Aquinas, "and she is therefore as little able to say to the sick of the palsy 'Rise up and walk.'"

In 1261 Aquinas was summoned to Rome by Urban IV., and for several years lectured there and in the principal cities of Italy. In 1263 he attended the Dominican chapter held in London. Two years after he declined the offer made to him by Clement IV. of the archbishopric of Naples, as well as the more congenial office of Abbot of Monte Cassino. In 1269 he again visited Paris; and in 1272 was recalled to Naples. In January 1274 he was summoned by Pope Gregory X. to attend the council convoked at Lyons to settle the differences between the Greek and Latin churches. Though suffering from illness, he at once set out on the journey. Finding his strength failing on the way, he was carried to the Cistercian monastery of Fossa Nuova, in the diocese of Terracina, quoting, as he entered the cloister, the words of the psalm "Hæc requies mea in secula seculorum?" After lingering for some weeks, he expired on the 7th of March 1274. About a century after, his body, for the possession of which many cities had eagerly contested, was removed to Toulouse, and buried with much pomp in the Dominican Church.

The highest honours which the church could bestow were awarded to the memory of Aquinas. The Angelic and Universal Doctor, the Angel of the Schools, and the Eagle of Theologians, were among the admiring titles conferred on the greatest of the schoolmen. He was canonized in 1323 by Pope John XXII.; and in 1567 Plus V. ranked the festival of St Thomas with those of the four great Latin doctors, Ambrose, Augustine, Jerome, and Gregory. Still higher is the honour implied in the fact that the repeated testimony of the church has stamped the authority of Aquinas with a kind of minor infallibility.

Any just estimate of his character and works would involve a view of the whole scholastic system, which attained in him its highest and most comprehensive development. The most philosophical of all the schoolmen, as his master Albert was the most learned, he consummated the harmony of the Aristotelic philosophy with the doctrines of the church; and to him mainly was due their all but exclusive empire till the era of the Reformation. With reference solely to his ethical system, Sir James Mackintosh (Prelim. Diss., p. 328) speaks of Aquinas as "the moral master of Christendom for three centuries." Those, indeed, who are accustomed to regard the scholastic philosophy indiscriminately as a system of mere laborious trifling, may find some scope for ridicule in the endless divisions and subtle questions of the Angelic Doctor on the nature and properties of angels and other impractical themes; but if the unvarying dialectical force and the occasional profound suggestiveness arouse no sympathy with the medieval admiration of "frater Thomas and his goodly lore," it is to be feared that the fault is not wholly with the writer. The mental fecundity which in so brief and interrupted a lifetime produced a mass of writings so voluminous, is in itself wonderful, but more remarkable is the power of continuous thinking which left its impress upon them all. The striking harmony of thought between Aquinas and Augustine, suggested the fanciful conception that the soul of the African bishop had reappeared after seven centuries in the body of the Italian monk. In him was again seen the union of the highest philosophical power with the most simple and fervent piety, the vigour and acuteness of a master-intellect, with the unearthly humility and devotion of the saint.

The best edition of the works of Aquinas (Rome, 1570-71) is in 17 vols. (18 tom.) folio. These consist of commentaries on Aristotle; commentaries on the Scriptures; the Summa Theologiae, his greatest work, and the most complete and extensive body of theological and moral science ever attempted; his Summa aduersus Gentiles; and miscellaneous pieces (Opuscula). They include also several Latin hymns.

The followers of Aquinas were called Thomists. Their fruitless contentions with the Scotists or disciples of the great Franciscan Duns Scotus, long divided the schools.