Isaiah), Postilla super Ieremiam (Commentary on Jeremiah) and Postilla super Threnos (Commentary on Lamentations). Then in 1252 he returned to Paris to study for the master's degree in theology. He lectured on the Bible as an apprentice professor, and upon becoming a baccalaureus Sententiarum (bachelor of the Sentences) he devoted his final three years of study to commenting on Peter Lombard's Sentences. In the first of his four theological syntheses, Thomas composed a massive commentary on the Sentences titled Scriptum super libros Sententiarium (Commentary on the Sentences). Aside from his master's writings, he wrote De ente et essentia (On Being and Essence) for his fellow Dominicans in Paris. In the spring of 1256 Thomas was appointed regent master in theology at Paris and one of his first works upon assuming this office was Contra impugnantes Dei cultum et religionem (Against Those Who Assail the Worship of God and Religion), defending the mendicant orders, which had come under attack by William of Saint-Amour. During his tenure from 1256 to 1259, Thomas wrote numerous works, including: Questiones disputatae de veritate (Disputed Questions on Truth), a collection of twenty-nine disputed questions on aspects of faith and the human condition prepared for the public university debates he presided over during Lent and Advent; Quaestiones quodlibetales (Quodlibetal Questions), a collection of his responses to questions posed to him by the academic audience; and both Expositio super librum Boethii De trinitate (Commentary on Boethius's De trinitate) and Expositio super librum Boethii De hebdomadibus (Commentary on Boethius's De hebdomadibus), commentaries on the works of 6th-century Roman philosopher Boethius. By the end of his regency, Thomas was working on one of his most famous works, Summa contra Gentiles. Naples, Orvieto, Rome (1259–1268) In 1259, Thomas completed his first regency at the studium generale and left Paris so that others in his order could gain this teaching experience. He returned to Naples where he was appointed as general preacher by the provincial chapter of 29 September 1260. In September 1261 he was called to Orvieto, where as conventual lector he was responsible for the pastoral formation of the friars unable to attend a studium generale. In Orvieto Thomas completed his Summa contra Gentiles, wrote the Catena aurea (The Golden Chain), and produced works for Pope Urban IV such as the liturgy for the newly created feast of Corpus Christi and the Contra errores graecorum (Against the Errors of the