ing, notably in his commentary on the Sentences; On Being
and Essence, on the meaning of certain metaphysical terms;
and in a short treatise entitled Principles of Nature. In the lat-
ter work he unequivocally defended (1) a real distinction be-
tween essence and existence (esse) in all creatures, (2) the pure
potentiality of primary matter, (3) absence of matter in spiri-
tual substance (substantia separata), (4) participation of all
created reality, material and immaterial, in God’s being
(esse), and (5) the Aristotelian dependence of abstracted uni-
versals on individually existing material things.
Under tense circumstances in the spring of 1256,
Thomas, though underage, was given license to incept by an
order of Pope Alexander IV dated March 3. When finally he
was allowed to incept, by an order of the pope dated June
17, he and his audience had to be protected by soldiers of
Louis IX because the animosity of the town and some stu-
dents against the mendicants was so great. William of Saint-
Amour’s antimendicant book On the Perils of the Last Days,
sent to Rome by the king for examination, was condemned
by the pope on October 5, and William was permanently ex-
iled from Paris by the king. Thomas’s reply to William’s
charges (Contra impugnantes Dei cultum et religionem), com-
pleted in late September or early October, arrived in Rome
after the pope had made his decision and, therefore, did not
influence the outcome.
Enjoying a respite from the antimendicant polemic,
Thomas lectured from 1256 to 1259 on the Bible, held scho-
lastic disputations (Quaestiones disputatae de veritate) over
three years, preached, and began composing his Summa con-
tra gentiles (1259–1264), apparently for Dominican mis-
sionaries in Spain and North Africa. This systematic summa-
ry in four books is an arsenal of sound and persuasive
arguments “against the gentiles,” that is, nonbelievers and
heretics.
Having served the order’s interests in Paris, Thomas re-
turned to Italy where he taught, wrote, and preached from
1259 to 1268. After spending two years in his home priory
of Naples, he was assigned to teach at Orvieto (1261–1265),
where he lectured to the community on Job and was of great
service to Pope Urban IV. At the pope’s request, he com-
posed the liturgy for the new Feast of Corpus Christi and ex-
pressed his views in Against the Errors of the Greeks on doctri-
nal points disputed by Greek and Latin Christians. Having
thereby discovered the richness of the Greek patristic tradi-
tion, he also began compiling a continuous gloss, or exposi-
tion, of the Gospels (Catena aurea), made up almost entirely
of excerpts from the writings of the Greek and Latin fathers,
dedicating the commentary on Matthew to Urban IV. In
June 1265, the provincial chapter of Anagni assigned Thom-
as to open a school of theology at Santa Sabina in Rome.
Soon realizing that Peter Lombard’s Sentences, then in com-
mon use, was unsatisfactory for young beginners, Thomas
projected a three-part survey of Catholic theology (Summa
theologiae) that would be simpler, more orderly, and more
inclusive than other works available. The first part was com-
pleted and in circulation by 1268. More subtle questions
were disputed in the Roman school in a special series on the
power of God (De potentia) and on evil (De malo). In addi-
tion, Thomas lectured on the Bible during this period.By the end of 1268, Thomas was ordered to return to
Paris, as was the Frenchman Peter of Tarentaise (the future
Pope Innocent V), to counter a revival of antimendicant sen-
timent among secular masters. When Thomas and his secre-
tary Reginald of Piperno arrived in Paris early in 1269,
Thomas realized that the situation was far more complex and
serious than he had assumed. Almost single-handedly he was
required to fend off attacks on three fronts: with all mendi-
cants against secular masters opposed to mendicants’ being
in the university; with a few of his confreres against most of
the Dominicans, Franciscans, and secular theologians, op-
posed to using Aristotle in theology; and with most theolo-
gians against young philosophers who tended to promulgate
heretical views under the name of Aristotle or his commenta-
tor Ibn Rushd (Averroës). Over the next five years Thomas
fulfilled his university obligations to lecture on the Bible, to
hold disputations, and to preach, while also carrying on a
vigorous polemic against the antimendicants, expounding all
the major works of Aristotle, writing his Summa theologiae,
and replying to numerous requests for his opinions.Revival of the antimendicant controversy under Gérard
d’Abbeville and his colleagues at Paris (encouraged by the ex-
iled William) centered largely on the role of evangelical pov-
erty in the spiritual life and on the practice of admitting
young boys into their novitiate. Thomas attacked the views
of Gérard in his quodlibetal disputations (1269–1271), in
two polemical treatises on Christian perfection, and in his
Summa (2.2.179–189). This phase of the controversy ended
with the death of its chief protagonists, William of Saint-
Amour on September 13, 1272, and Gérard at Paris that
same year on November 8.On December 10, 1270, thirteen philosophical proposi-
tions opposed to the Catholic faith were condemned by
Étienne Tempier, bishop of Paris. To prevent such views
from developing in the classroom, Thomas undertook a de-
tailed literal commentary on all the main texts of Aristotle
then in common use at the University of Paris. It is possible
that Thomas began his commentary on De anima in Italy,
but all the others were written after his return to Paris in
1269, namely, the commentaries on Physics, On Interpreta-
tion, Posterior Analytics, Ethics, Metaphysics, Politics, and cer-
tain others left unfinished at his death. Because all these
works of Aristotle were used as textbooks in the arts faculty
and had to be taught by the young masters whose best guide
to date had been Ibn Rushd, Thomas therefore felt a particu-
lar urgency in writing his own commentaries that remained
closer to the original sources and within the context of Chris-
tian faith. His unfinished expositions of Aristotle’s De caelo,
De generatione, and Metheora were among his last writings
at Naples.THOMAS AQUINAS 9161