Giles of Rome (c. 1247–1316)

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(c. 12471316)

Giles of Rome, the scholastic philosopher whose real name was Aegidius Colonna Romanus, was born in Rome. Giles entered the Augustinian order of hermits in 1265 and subsequently studied at the University of Paris, where from 1268 to 1272 he was probably the pupil of Thomas Aquinas, who was then lecturing at the university as Dominican regent master. In 1277 the bishop of Paris made his far-reaching condemnation of 219 theses, mainly of Aristotelian origin but also including a number of Thomist propositions. Among these were Thomas's doctrine that each being contains only one substantial form, as opposed to the traditional Augustinian belief in a plurality of forms. Giles, a young scholar, joined in the ensuing controversy with the publication of a sharply worded defense of the Thomist view, the Liber Contra Gradus et Pluralitatem Formarum. He attacked the Augustinian doctrine as being contrary to both reason and faith. Upon his refusal of Bishop Tempier's demand for a retraction, Giles left Paris, perhaps for a cooling-off period, but returned in 1285 to take the first Augustinian chair in theology and to receive his license to teach. He remained a professor until 1292, when he was appointed prior general of his order. In 1295 Pope Boniface VIII appointed him archbishop of Bourges, in which office he remained until his death. In 1287 his teachings had become the official doctrine of the Augustinian order, although neither of the other great Augustinian thinkers of the fourteenth century, Thomas of Strasbourg and Gregory of Rimini (each a general of the order) followed his teachings.


Giles's philosophical position still remains something of an enigma. The older view that he was strictly a disciple of Thomas has gradually been modified. While it is true that he reached substantially the same conclusions as Thomas on two of the burning issues of the day, the unity of the substantial form and the distinction between essence and existence, neither of these seems to have been from Thomist premises and, in the case of the second issue, the conclusion did not even lead to the same doctrine. In particular, Giles seems to have been influenced to a far greater degree than Thomas by Neoplatonism, and especially Proclus, on whose Liber de Causis he commented in 1280. This affinity would explain his own treatment of the relation of essence to existence. Thomas had never made a real distinction between the two but had regarded them rather as a composition in which esse is the actuality of essentia, which is itself the source of a being's actuality; or put another way, a being is what it is in virtue of the actuality (esse ) that derives from its form (essentia ). For Giles, on the other hand, esse and essentia were distinct things (res ) from the outset. He therefore treated as real what for Thomas were abstractions, an attitude confirmed in his Commentary on the Liber de Causis, where he thought in terms of a universe of intelligible beings. To attain intelligible knowledge, it suffices for the image of an object to act directly upon the possible intellect, which under the influence of the active intellect is able to conceive it as an intelligible species. This led Giles to the characteristically Platonic conclusion "that the same quiddity considered in things is particular, considered in the mind is universal."

Scientific Contributions

Although knowledge of Giles's scientific outlook is even less comprehensive than that of his philosophical system, his treatment, often Neoplatonic, of time, movement, gravity, quantity, the intensification and remission of forms, and matter is known to us. Giles made his most original and important contribution to later scholastic scientific discussion concerning the nature of quantity. He posited a twofold quantity (duplex quantitas ) that corresponds to the modern distinction between mass and volume. On the one hand, a body contains a constant quantity of matter, which limits its possibilities of development; for instance, a barleycorn cannot become a mountain. On the other hand, the same quantity of matter can undergo various changes in dimension, and according to its volume it will be denser or rarer in structureas with, say, water or air. Giles took this distinction to infer that mass and volume were thus two independent quantities.

Giles also distinguished sharply between form and matter in the structure of a material substancethe so-called problem of the mixtum. This raised the question of what happened to the forms of the four material elementsfire, earth, air, and waterwhich composed any material substance when they were combined with form of that substance, for example, wood. Did they continue to exist separately, or were they absorbed into the substantial form? This was one of the earliest scientific problems to exercise the Scholastics, and while Giles based himself upon what Thomas had already said, he also went further. He accepted Thomas's solution that the forms of the material elements, once included in a material substance, no longer remained formally and actually in being but, rather, virtually as part of the qualities of the substance. To this, however, he added the distinction between the material and formal qualities. The former (ex parte materiae ) remained the same through all changes in the substance; the forms, on the other hand, could not remain numerically the same. Another aspect of Giles's mixtum theory was of a hierarchy (ordo realis ) among substantial forms, in which each higher form virtually contained the lower forms, the higher form being able to do more perfectly whatever the lower form could do.

Giles was also the first among the high Scholastics to state explicitly the problem of the increased speed of a falling body, namely, that this was not caused by the approach of its destination but rather by the growing distance from its starting point. Again, concerning a falling body in a vacuum, a problem which was to exercise successive generations of fourteenth-century thinkers, Giles was the first to pose it directly, taking a standpoint different from that of Thomas. In his Commentary on Aristotle's Physics, Giles posed other original questions about movement: Whether the sole cause of why movement took place in time, and not instantaneously, was resistance to the mover from the medium in which it moved, and whether in a vacuum movement itself would be composed of a succession of instants which in themselves did not constitute time. To both Giles answered in the affirmative. Thus the difference between movement in a medium and movement in a vacuum was that in the first case it was successive as opposed to instantaneous, owing to the resistance encountered; in a vacuum, on the other hand, it was motus discretus in tempore discreto. There can be little doubt from what is already known of his scientific speculation that Giles was the forerunner of the scientific inquiry so characteristic of the fourteenth century.

Political Philosophy

Giles had been tutor to the future Philip IV (the Fair) of France, to whom he dedicated his De Regimine Principium. This work, stressing the Aristotelian view of a ruler, was based upon the Ethics and Politics. But with the outbreak of the struggle between Philip IV and Pope Boniface VIII in 1296, Giles took the pope's side. His De Potestate Ecclesiastica (probably written c. 1302) stated, in the most extreme form yet, the Augustinian view of society, in which the spiritual power is superior to the temporal and only the faithful can possess the just and righteous lordship derived from the universal lordship of the church. Lordship is a gift from God, and justice is submission to God through the church; hence, sin deprives the sinner of all right of lordship. Giles here sowed the seeds of the doctrine of dominion and grace that was to be developed by Richard FitzRalph and then turned against the church by John Wyclyf.

See also Aristotelianism; Aristotle; Augustinianism; Gregory of Rimini; Liber de Causis; Neoplatonism; Proclus; Thomas Aquinas, St.; Thomism; Wyclyf, John.


works by giles

Commentaries on Aristotle

Physics. Padua, 1483; Venice, 1492.

Posterior Analytics. Venice, 1488.

De Anima. Venice, 1496.

Prior Analytics. Venice, 1499.

Expositio in Artem Veterem. Venice, 1507.

Metaphysics. Venice, 1550.

Other Works

Quodlibeta. Venice, 1496.

"De Intellectu Possibili" and "De Gradibus Formarum." In De Anima. Venice, 1550.

Super Authorem Libri de Causis Alfarabium. Venice, 1550.

Commentary on the Sentences. Córdoba, 1707.

De Ecclesiastica Potestate. Edited by R. Scholz. Weimar: Böhlaus Nachfolger, 1929.

Aegidii Romani Theoremata de Esse et Essentia, edited by Edgard Hocedez. Louvain, 1930.

works on giles


Boffito, G. Saggio di bibliografia egidiana. Florence, 1911. A bibliography.

Egenter, R. Die Erkenntnispsychologie des Aegidius Romanus. Regensburg, 1926.

Hocedez, E. "Gilles de Rome et Henri de Gand sur la distinction réelle, 127687." Gregorianum 8 (1927): 358384.

Hocedez, E. "Gilles de Rome et saint Thomas." In Mélanges Mandonnet, edited by P. Mandonnet. 2 vols. Paris: Vrin, 1930. Vol. I, pp. 385409.

Makaay, S. Der Traktat des Aegidius Romanus über die Einzigkeit der substantiellen Form. Würzburg, 1924.

Mandonnet, P. "La carriere scolaire de Gilles de Rome (12761291)." Revue des sciences philosophiques 4 (1910): 480499.

Nardi, B. "Egidio Romano e l'avverismo." Rivista di storia della filosofia 3 (1947): 197220; 4 (1948): 122.

Paulus, J. "Les disputes d'Henri de Gand et Gilles de Rome sur la distinction de l'essence et de l'existence." Archives d'histoire doctrinale et littéraire du moyen âge 15 (19401942): 323358.


Maier, A. An der Grenze zwischen Scholastik und Naturwissenschaft im 14 Jahrhundert. Rome: Edizioni di Storia e Letturatura, 1951.

Maier, A. Metaphysische Hintergründe der spatscholastischen Philosophic. Rome: Edizioni di Storia e Letturatura, 1956.

Maier, A. Die Vorläufer Galileis, 2 vols. Rome, 1949.

Maier, A. Zwei Grundprobleme der scholastische Naturphilosophie. Rome: Edizioni di Storia e Letturatura, 1951.

Maier, A. Zwischen Philosophic und Mechanik. Rome: Edizioni di Storia e Letturatura, 1958.

Political Philosophy

Gwynn, Aubrey. The English Austin Friars in the Time of Wyclif. London: Oxford University Press, H. Milford, 1940.


Gilson, Étienne. History of Christian Philosophy in the Middle Ages, 735736. London: Sheed and Ward, 1955. Complete bibliography.

Gordon Leff (1967)