The Greek version of Claudius Galen’s On the Usefulness of the Parts [Περὶ χρησέως μορίων: Peri chrēséōs moríōn], an important book in terms of both the history of medicine and theology, has survived to this day. This work by Galen was translated into Arabic under the name Fī Manāfi’ al-’Adā’ by Ḥunayn Ibn ‘Isḥāq in Baghdad in the 9th century during the translation movement in the Islamic civilization. This article aims to observe the changes Ḥunayn made in the text by generally focusing on specific terms and phrases. Particularly, this will be achieved by comparing the English translation of Galen’s Greek original work with its Arabic translation. And this will be specifically accomplished by drawing attention to Ḥunayn’s method and approach of translation in adapting Galen’s work On the Usefulness of the Parts to Islamic culture. It is clear that the term “Islamic culture” encompasses a vast array of concepts. However, for the purposes of this article, our focus will be on Islam’s robust monotheistic principles, its rejection of pagan notions, and the unique phrases that can be traced back to the Qur’ān. Elvira Wakelnig described this translation approach as a method wherein the “Greek material was clothed in Islamic garb”. The reason for choosing this particular book stems from the fact that its topic is closely related to rational theology and it has arrived to us in a complete form in both its original Greek language as well as in its Arabic translation made by Ḥunayn.