 A great deal of translations made under the reign of al-Ma’mun (r. 813–833) and his successors are extant. The new interpretation of Islam and of the role of the caliph promoted by  al-Ma’mun,[20]  as well as the increasing interest in the secular sciences of the elites of Islamic  society,[21]  created the context for the development of the translations into Arabic. Even though the court library (Bayt al-hikma,“House of  Wisdom”)[22]  cannot be viewed as an institutional center for the translations of Greek works into  Arabic,[23]  a close relationship existed between the activities of the first group of translators and the court. The leader of this group, the encyclopaedic scientist and first faylasuf Abu Yaʿqub ibn Ishaq  al-Kindi,[24]  was appointed as the preceptor of the son of the successor of al-Ma’mun, al-Muʿtasim (r. 833–842): one of Kindi’s works is addressed to al-Ma’mun, whereas his major metaphysical writing, On First  Philosophy,[25]  is addressed to al-Muʿtasim. How do we know that there was a group of translators and that al-Kindi was its leader? The ancient sources give a hint to this, in so far as they mention, for instance, that the earliest translation of Aristotle’s Metaphysics was made for  him.[26]  Also, the incipit of the well-known  Theology of Aristotle  claims that he acted as the revisor of this work, in fact an adapted translation of parts of Plotinus’ Enneads IV–VI. Since it has been established (Endress 1973) that the same lexical and syntactical features of the two translations just mentioned are shared by other translations from Greek, one can be reasonably sure that several translators exchanged among themselves and with al-Kindi: the latter has been described as the spiritus rector of this group (Endress 1997a; 2007). The translations of this circle include works by Plato, Aristotle, Nicomachus of Gerasa, Alexander of Aphrodisias, Plotinus, Proclus, John Philoponus and Olympiodorus. It is worth noting that the texts of Plotinus, and in part those of Proclus and Philoponus, did not circulate under the names of their authors: Plotinus circulated under the name of Aristotle (Rosenthal 1974), Proclus under those of Aristotle and Alexander of Aphrodisias, and Philoponus under the name of Alexander (see below).