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.
[6] According to a tradition that can be traced to shortly after Thomas's death, the Summa contra Gentiles was written in response to a request, made in 1259, for a book that would help the Dominican missionaries in Spain to convert the Muslims and Jews there.
To this end, Raymond instituted the teaching of Arabic and Hebrew in several houses of the friars, and he also founded priories in Murcia (then still under Muslim rule) and in Tunis.
Raymond's request to Thomas was transmitted by fellow Dominican Ramón Martí, one of eight friars appointed to make a study of oriental languages with the purpose of carrying on a mission to Jews and Moors.
In September 1261 he was called to Orvieto as conventual lector responsible for the pastoral formation of the friars unable to attend a studium generale.
The structure of St. Thomas's work is designed to proceed from general philosophical arguments for monotheism, to which Muslims and Jews are likely to consent even within their own respective religious traditions, before progressing to the discussion of specifically Christian doctrine.
In the mid-1650s Ciantes wrote a "monumental bilingual edition of the first three Parts of Thomas Aquinas’ Summa contra Gentiles, which includes the original Latin text and a Hebrew translation prepared by Ciantes, assisted by Jewish converts, the Summa divi Thomae Aquinatis ordinis praedicatorum Contra Gentiles quam Hebraicè eloquitur….