There is a certain line of contemporary Catholic apologetic, more superficial than substantive, which has become fashionable in recent decades and runs generally like this: Because the Fathers of the Church, and later medieval giants such as St. Thomas Aquinas, drank from the wells of pagan philosophy, it is permissible, indeed laudable, for today’s Catholics to “engage” or “dialogue” with non-Catholic—even non-Christian or secular—“thought.” I use the term “thought” here loosely because oftentimes the “engagement” or “dialogue” being encouraged has more to do with religious-cultural traditions rather than any product of natural reason. That fact alone is more than sufficient to distinguish what St. Thomas was doing with the Corpus Aristotelicum from what certain fashionable Catholics have tried to do with, say, Buddhism or Vodun. Sticking with the realm of thought for a moment, it is necessary to note that even up until relatively recent times the Catholic “engagement” (or one might say “critique”) with non-Catholic (atheistic) philosophy was carried out in defense of the Faith and the Catholic intellectual tradition rather than a questionable attempt to artificially graft on some “alien wisdom.” Fr. Erich Przywara’s complex, and still widely misunderstood (or perhaps just underappreciated), critical engagement with Martin Heidegger comes quickly to mind. The Scholastic pushback against Modernism, which at best is only superficially Christian, is another example.
One way to do an end-run around all of this is to stress the cultural and/or religious context of the thought St. Thomas—and to a lesser extent the Church Fathers before him—dealt with in their respective writings. Before proceeding, it is worth highlighting that the Church Fathers are less useful for this project for two important reasons. First, the Church Fathers were not in uniform agreement on the usefulness of pagan philosophy for the enterprise of Christian philosophy, and the early centuries of the Church are filled with numerous examples of learned churchmen—some admittedly more orthodox than others—drawing either too near, or drifting too far away from, the intellectual patrimony of the Greco-Roman world. Second, the Fathers were unequivocal in their affirmation of Christianity, with many devoting considerable resources (if not their lives) to refuting any and all attempts to synthesize the Gospel with various pagan cults and religions. These men did not seek a “higher,” “more enlightened,” or “fully realized” form of Christianity by “dialoguing” with false religions; they did, however, seek to bring those ensnared by error to the full knowledge of the Truth so that their souls might be saved.
St. Thomas, unfortunately, is easier to draw into the contemporary Catholic apologetic for “engagement” or “dialogue” for the apparently simple fact that he is alleged to have “engaged” or “dialogued” with Islamic and Jewish philosophy. This claim runs into an immediate difficultly, though. What exactly is meant by Islamic philosophy and Jewish philosophy? Sticking with Islam (which is arguably more controversial), is the philosophy Aquinas “engages” or “dialogues” with philosophy—the exercise of natural reason—that happens to come from Muslims or is there something specifically Islamic about it? And, in that case, is it even philosophy and not, rather, Islamic theology premised on the tenets of the (false) Mohammedan religion? Further, if what is at issue is Islamic theology, is there any reasonable way to claim that Aquinas “engaged” or “dialogued” with that theology in the manner contemporary Catholics intoxicated by either syncretistic trends (cf. Assisi Gatherings) or the bald importation of secular-liberal thinking into the Church mean when they use the words “engage” or “dialogue”? To help answer that question, perhaps it is best to let the Angelic Doctor speak for himself when it comes to the Muslim religion (Summa Contra Gentiles, Book 1, Chapter 16, Art. 4, Footnote 1):
He [Mohammed] seduced the people by promises of carnal pleasure to which the concupiscence of the flesh urges us. His teaching also contained precepts that were in conformity with his promises, and he gave free rein to carnal pleasure. In all this, as is not unexpected; he was obeyed by carnal men. As for proofs of the truth of his doctrine, he brought forward only such as could be grasped by the natural ability of anyone with a very modest wisdom. Indeed, the truths that he taught he mingled with many fables and with doctrines of the greatest falsity.
He did not bring forth any signs produced in a supernatural way, which alone fittingly gives witness to divine inspiration; for a visible action that can be only divine reveals an invisibly inspired teacher of truth. On the Contrary, Mohammed said that he was sent in the power of his arms – which are signs not lacking even to robbers and tyrants. What is more, no wise men, men trained in things divine and human, believed in him from the beginning. Those who believed in him were brutal men and desert wanderers, utterly ignorant of all divine teaching, through whose numbers Mohammed forced others to become his follower’s by the violence of his arms. Nor do divine pronouncements on part of preceding prophets offer him any witness. On the contrary, he perverts almost all the testimony of the Old and the New Testaments by making them into a fabrication of his own, as can be seen by anyone who examines his law. It was, therefore, a shrewd decision on his part to forbid his followers to read the Old and New Testaments, lest these books convict him of falsity. It is thus clear that those who place faith in his words believe foolishly.
Setting aside how unfashionable these words would be among many Catholics today, it is undoubtedly clear that St. Thomas saw Islam for what it is: a false religion. So then are we to believe that Aquinas “engaged” or “dialogued” with Islam in order to learn something from it which might help illuminate, perhaps even expand, the depositum fidei? Did he seek, on the mutual basis of the Revelation of God and the “revelation” (false teachings) of the “Prophet” Muhammad, a “higher religion” or, at least, “higher religious understanding”? It seems not. For as St. Thomas sets forth at the opening of the Summa Contra Gentiles, his mission was to articulate and naturally demonstrate the core truths of Catholicism which even Muslims mired in religious error, though hardly deprived of reason, could accept. Thomas, appealing in part to a shared philosophical heritage inherited from the pagans, sought to win souls for the Catholic Faith, not distort or compromise his own religion by imbibing error under the guise of “tolerance,” “pluralism,” or “cultural diversity.” Additional confirmation that Aquinas was not interested in a contemporary form of either “engagement” or “dialogue” can be found in the fact that he dedicates a substantial portion of De Rationibus Fidei contra Saracenos, Graecos et Armenos ad Cantorem Antiochenum to defending tenets of the Faith, such as the doctrine of the Holy Trinity and the Incarnation, from Muslim criticism rather than trying his hand at internalizing those critiques for the purpose of establishing “mutual sympathetic understanding” between Light and darkness.
As for the scholarly question of how well-read Aquinas was in Islamic philosophy (i.e., philosophy written by Muslims), that cannot be addressed in any detail here. What can be noted in closing, however, is that to the extent Aquinas read and learned from Islamic philosophers, he did so because they were philosophers, not because they were Muslims. Let it not be forgotten either that St. Thomas was not shy about pointing out the defects found among certain Islamic philosophers while leverage his knowledge of their works in defense of the Faith and for the salvation of souls.