c. 1243-1316

Italian scholar who supported the doctrine of substance put forth by Thomas Aquinas (c. 1225-1274). An Augustinian hermit also known as Aegidus Romanus and Doctor Fundatissimus ("Best-Grounded Teacher"), Giles may have studied under Thomas in Paris between 1269 and 1272. Some years later, defending Thomistic substance in particular—and Scholasticism in general—against attacks from the higher clergy, he wrote Theoremata de esse et essentia (Essays on being and essence). He also produced commentaries on the Organon, writings concerning logic by Aristotle (384-322 B.C.).