Summa contra Gentiles

The Summa contra Gentiles (also known as Liber de veritate catholicae fidei contra errores infidelium "Book on the truth of the Catholic faith against the errors of the unbelievers") is one of the best-known books by St Thomas Aquinas, written during c. 1259–1265.

It was probably written to aid missionaries in explaining the Christian religion to and defending it against dissenting points of doctrine in Islam and Judaism. To this end, Aquinas may rely on a substantial body of shared doctrine, especially tenets of monotheism, in the case of Judaism the shared acceptance of the Old Testament as scripture and in the case of Islam the (at the time) shared tradition of Aristotelian philosophy. Whereas the Summa Theologiæ was written to explain the Christian faith to theology students, the Summa contra Gentiles is more apologetic in tone, as it was written to explain and defend the Christian doctrine against unbelievers, with arguments adapted to fit the intended circumstances of its use, each article refuting a certain heretical belief or proposition. Instead of a mere elucidation of the length and breadth of Christian doctrine, Aquinas explains specific core articles of Christian belief.

The work was written over a period of several years, between 1259 and 1265.

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, 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, and he was working on Summa contra Gentiles by the time he left Paris. From Aquinas' autograph, Torrell (1996) identified the first 53 chapters of Book I as having been written in Paris based on studies of the parchment and the ink used.

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