Abstract

Aquinas’ Summa contra Gentiles (SCG), in its apologetic discourse aimed at Jews and Muslims of the Latin Christendom, strategically engages with Islamic and Jewish sages of its scholastic era. Since existing scholarship has not sufficiently qualitatively and quantitatively evaluated Aquinas’ most frequently referenced Islamic and Jewish philosophers in SCG, leaving a significant scholarly lacuna, this study addressed the gap by analyzing Aquinas’ direct references to and argumentative engagements with Avicenna, Averroes, Maimonides, and Avicebron, showing their distribution, Aquinas’ argumentative stance of agreements, partial agreements/disagreements, or disagreements, and purpose of these reference-based arguments, categorized as either Aquinas’ aim to refute the referenced proposition or utilize it to support, build upon, and advance his thesis. The methodology employed a dual analytical approach, consisting of a qualitative textual-philosophical analysis of the SCG text in the scholarly authoritative Editio Leonina, cross-verified against Vansteenkiste’s studies and Busa’s Index Thomisticus, followed by a quantitative assay. The results revealed that Aquinas directly referenced the Islamic and Jewish philosophers 61 times in the SCG’s 415 Capitula. Islamic philosophers (95%) Averroes (64%) and Avicenna (31%) are the most prominent. In contrast, Jewish philosophers, Maimonides and Avicebron, comprise only a minor fraction. These references are concentrated in SCG II, followed by SCG III and SCG I. The SCG IV, which deals with the Latin Catholic dogmatic theology, has only one direct reference to Avicenna. Aquinas often engaged with these philosophers through argumentative disagreements (81%), primarily based on Averroes’ arguments and secondarily on Avicenna’s. However, he never refuted the relatively few agreements (14%) and partial agreements (5%), instead utilizing them to build upon, advance, and support his thesis. Aquinas never agreed with Maimonides and Avicebron and always used these argumentative disagreements to refute their philosophical propositions. This pattern exhibits a strong correlation between Aquinas’ argumentative agreement level and purpose of direct reference-based argument, illustrating the Thomistic method of theological discernment, characterized by Aquinas’ selective appropriation, adaptation, and adoption of the other two Abrahamic traditions’ philosophies when compatible with the Latin Church’s teachings, and systematic refutations when incompatible, terming them ‘errors’ that must be countered. This study demonstrates that the Thomistic theological synthesis of Islamic and Jewish philosophy in Aquinas’ SCG Sacra Doctrina not only strengthened Thomistic theology and defended the Roman Catholic faith but also succeeded in bridging the three Abrahamic monotheistic traditions, Christian, Islamic, and Jewish, through their shared Peripatetic philosophy of universal truth, the truth that commences in God.