   The scientifically rich Hellenistic culture to which Islam was heir is evident in the work of Abû Yûsuf Ya‘qûb ibn Ishâq al-Kindî (d. c.870) and Abû Bakr Muhammad ibn Zakariyya ibn Yahya al-Râzî (865-925 or 932). Al-Kindî, known as “the philosopher of the Arabs” for his Arabian genealogy, was active, with others of his circle, in editing Arabic translations and paraphrases of both Aristotelian and Neoplatonic texts. He also was familiar with other branches of Greek science, and wrote treatises on many diverse topics. His views on psychology were formed mainly by acquaintance with paraphrases made of De anima, the Theology of Aristotle (An abridgement of Plotinus' Enneads) and the Book on the Pure Good (an abridgement of Proclus' Elements of Theology, known in Latin as Liber De Causis). An Arabic version of Euclid's Optics also helped al-Kindî develop his theory of vision, expressed in his De Aspectibus and two smaller treatises (extant in Arabic only). Unfortunately, al-Kindî does not integrate his understanding of vision with other aspects of his psychology, the parts never amounting to a whole, complete system. We have instead a fragmentary report indicating directions in which al-Kindî was headed, and probable sources with which he had some acquaintance.