AQUILEIA (med. Aglar, Slovene Vogle j) , a former city of the Roman empire and mediaeval Western Patriarchate, situated at the head of the Adriatic, six miles inland, and 22m. west-north west of Trieste; it is now a mere village.
Aquileia was founded by the Romans 181 B.C. to prevent the irruptions of barbarians along the narrow strip between the Alps and the Adriatic. Here the Postumian Way terminated; beyond, the roads branched out to Illyria, Pannonia and Noricum. Its situation soon made it a commercial and military centre of the first importance. It was connected by canal to the sea at Grado, which was joined by a causeway to the mainland, and here part of the Roman fleet was stationed. Its trade increased rapidly after Pannonia and Illyria became part of the Roman Empire. It was the capital of the province of Venetia, and the only city in Italy, beside Rome, which had the right of striking coins. Ausonius ranks it as the fourth Italian town, after Rome, Milan and Capua. Under Hadrian it had between 300,00o and 500,000 inhabitants. In A.D. 452 it was taken by the Huns, after a three months' siege, and razed to the ground. The surviving inhabitants fled for safety to the neighbouring lagoons. The only importance left Aquileia was as an ecclesiastical centre. Aquileia had been the seat of a very old bishopric. Tradition ascribes its foundation to St. Mark, and its early incumbents included SS. Hermagoras, Hilarius and Valerian. In the 5th and 6th centuries its diocese included all of north-east Italy, with Illyria, Noricum and Rhaetia, and it was thus the chief ecclesiastical power among the eastern Germanic tribes. Its bishop Macedonius (535-556) refused to acknowledge the conclusions of the 5th Oecumenical Council (5 53) and seceded from Rome at the head of the bishops of north Italy, Venetia and Istria, assuming in 557 the title of Patriarch, which had been accorded to him by the barbarians. Soon after, Italy was overrun by the Lombards, and the patriarch fled to Grado, six miles away. The Metropolitan Candidian of Aquileia (in Grado) made submission to the pope in 6o6, but his Lombard suffragan did not follow him and there were for long rival patri archs of both Aquileia and Grado. But Poppo of Aquileia sacked Grado in 1024 and carried off its treasures to Aquileia, where he built the present cathedral (consecrated 1037). The Emperor Conrad supported him in the resultant war with Venice, granted him the fief of Istria, with the right to strike coins, and forced Pope John XX. to recognize him as metropolitan of all Italy, after Rome. From this time onward, the city was overshadowed by Venice, which finally deprived Aquileia of all territories be stowed on it by the Empire (1420). In 1438 the city itself was destroyed by an earthquake ; the next patriarch acquiesced in the loss of his old power in return for an annual payment of 5,000 Venetian ducats . Henceforward the patriarch resided at Udine, of which city he was to all intents bishop, and Venice claimed the sole right of appointing the incumbents. This right was disputed by the rulers of Austria, some of whose recently acquired territories lay within the see of Aquileia. At last Pope Benedict XIV. was chosen as arbiter, and in 1748-49 abolished the patriarchate (then represented by its I09th incumbent, Daniel Delfino) altogether.
C. A. M. AQUINAS, THOMAS (THOMAS OF AQUINO) (I225?— 1274), the prince of scholastic philosophers, known as Doctor Angelicus, was born at the castle of Roccasecca, near Aquino in the province of Naples. Having received his elementary educa tion at the abbey of Monte Cassino, in 1239 he went to study the seven liberal arts at the University of Naples. There, five years later, he entered the Order of St. Dominic, against the wishes of his family. From 1245-48 he studied in Paris under Albert the Great, and when Albert returned to Cologne in 1248 Thomas went with him. In 1252 he was again in Paris, where, in 1256, after composing the commentaries on the Bible and on the Sentences, he received the degree of Licentiate in Theology, and shortly after wards that of Master in Theology. For the next few years he was engaged in teaching and defending the rights of his Order against William of St. Amour, the spokesman of the University of Paris. From 1259-68 he taught at the Pontifical Curia in Rome, and again in Paris from 1268-72, where he began his opposition to Siger of Brabant and the Latin Averroists, and to the Franciscan supporters of Augustinianism. In 1272 he was recalled to his native country, to teach at Naples. Like his friend, St. Bonaven ture, he was summoned by Gregory X. to the General Council of Lyons (1274), which proposed to reconcile the differences be tween the Greek and Latin Churches, but while on his way to Lyons he died on March 7, 12 74.
All the many writings of St. Thomas are preparatory to his great work, the Summa Theologica. He began in 1254 with his Commentary on the Sentences of Peter the Lombard, a work in which the influence of Albert the Great and of the Augustinianism that he was to desert later, is very evident. Then came his de liverances upon speculative theological problems in some of his early Quaestiones disputatae and the Quaestiones quodlibetales, and his commentaries upon certain of the Scriptures. About the same time he was producing commentaries on Boethius, on the De divinis nominibus of pseudo-Dionysius, on the Liber de Causis, and on the following works of Aristotle : the Physics, Metaphysics, De Anima, De Sensu, De Memoria, Ethics, Politics, Posterior Analytics, Meteors, Peri Hermeneias, De Caelo and the De Generatione. Most of the important doctrines of all these works and the later Opuscula, are set forth in a simplified manner in the two great Summae, the Summa contra Gentiles, and the Summa Theologica.
In the Summa contra Gentiles (1259-64), the chief work of the middle ages on natural theology, St. Thomas attempts to meet the views and objections of non-Christians by clearly distinguish ing the spheres of natural reason and faith. Reason and faith, he thinks, are both concerned with the same object, but in different ways ; the former starts from sense-data, and attains to a knowl edge of the existence, the unity, the goodness, the intelligence and the will of God ; the latter rests on revelation and authority, and attains to a knowledge of God as a purely spiritual Being, e.g., a Being with a Trinity of Persons. Each requires to take into account the knowledge arrived at by the other, and, on account of the difference in their methods, there need be no fear of con tamination ; they cannot be confused and they should not be iso lated. Of the two, faith is the more important, because it bestows on man a knowledge which he could not ordinarily possess, and thus it is said to transcend reason. True reason and faith can never be contradictory, for they both come from the one source of all truth, God, the Absolute One.
After 1265, St. Thomas began his Summa Theologica, which he intended to be the sum of all known learning. It is divided into three parts, which may be said to treat of God, Man and the God Man. The first and the second parts are wholly the work of the angelic doctor; but of the third only the first 90 questions are his; the rest of it was finished in accordance with his designs by Reginald of Piperno. Part I., after a short introduction upon the nature of theology, proceeds to treat of the existence of God, of His nature and attributes, of the Trinity, of the Creation, of problems pertaining to the angels and to man, and lastly, of the divine government of the world. Part II. includes the Prima Secundae and the Secunda Secundae, the former embracing gen eral morality as founded on the ethics of Aristotle and including man's end, his will, the passiones of his soul, virtue in general, sin, the old law and the new law of grace—the latter dealing with special morality, including the theological and cardinal virtues which raise numerous practical issues, and the contemplative life (see ETHICS). In the third part of the Summa, St. Thomas dis cusses the Person, office and work of Christ, and had begun to dis cuss the sacraments when death ended his labours ; addi tions to complete the scheme are appended as a Supplernenturn Tertiae Partis.
BIBLIOGRAPHY.-The best modern edition of the works of Aquinas Bibliography.-The best modern edition of the works of Aquinas is the Leo XIII. edition (Rome, 1882) ; 13 volumes have appeared. For works not yet in this edition, see the Vives edition, 34 vols. (1872-8o) . The S. Theologica, the S. c. Gentiles and most of the Quaestiones also exist in practical editions produced by P. Marietti (Torino), and the first two have been translated into English by the Dominican Fathers.
For the life and works of St. Thomas consult Mandonnet, "Chro nologie sommaire de la Vie et des Ecrits de S. Thomas," in Rev. des Sciences Phil. et Theol., p. 542 seq. (1920), and Des Ecrits Authen tiques de S. Thomas d'Aquin (Fribourg, 2nd ed. 191o) ; Grabmann, Die echten Schriften des hl. Thomas v. Aquin (Munster, 192o). Of the innumerable works on the thought of St. Thomas—most of which have been listed in tberweg, Grundriss der Geschichte der Philosophie (1915), and in Mandonnet et Destrez, Bibliographic Thomiste (Bibliotheque Thomiste), vol. i., published by the Rev. des Sciences Phil. et Theol. (Le Saulchoir, 192I)--some of the most im portant are: St. Thomas Aquinas: Being papers read at the sixth centenary celebrations (Oxford, 1925) ; P. Duhem, Le Systeme du Monde, vol. v. ch. 12 (1917) ; E. Gilson, Le Thomisme, Eng. trans. by E. Bullough (1924), and Saint Thomas d'Aquin (a study of his ethics) (1925) ; M. Grabmann, Thomas v. Aquin (Munich, 1912) ; Guttmann, Das V erhdltnis des Thomas v. Aquin zum Judentum (Got tingen, 1891) ; Mandonnet, Siger de Brabant (Louvain, 1911) ; Rohner, Das Schopfungsproblem bei Moses Maimonides, Albertus Magnus u. Thomas v. Aquin (Munster, 1913) ; Rousselot, L'Intellectualisme de Saint-Thomas (2nd ed. 2924) ; J. Schwane, Dogmengeschichte der mittleren Zeit (Freiburg i. B., 1882) ; A. D. Sertillanges, S. Thomas d'Aquin (191o), and La Philosophic morale de S. Thomas d'Aquin (1916) ; C. C. L. Webb, Hist. of Natural Theology (1915) ; P. Wick steed, Dante and Aquinas (1913), and The Reactions between Dogma and Philosophy illustrated from the works of St. Thomas Aquinas (192o) ; de Wulf, Mediaeval Philosophy illustrated from the System of St. Thomas Aquinas (Harvard, 1922).