When we study Scholastic philosophers of the Middle Ages, and learn that they laid the rational foundations for modern physics and chemistry, we learn about intellectual giants like Abelard and Ockham, and how they pushed the limits of logic to include innovative forms of argumentation.
Philosophers like Abelard and Aquinas did not work in isolation. They were in dialogue with Arabic philosophers. Despite political and religious tensions between the Europeans and empires of the Near East, the philosophers corresponded. Neither side had any difficulty in simultaneously calling the other "godless heretical infidels" and yet respecting the intellectual and academic accomplishments of the other.
The beginnings of Arabic philosophy came with the translation of large numbers of philosophical works into Arabic from Greek. The works were primarily those of Aristotle, Plato, and the later Neo-Platonists. Curiously, many of these works were translated by Christian Arabs, at the end of era of Arabic Christianity and the beginning of the era of the hegemony of Islam in Arabic culture. We need to remember that, prior to the Islamic invasions, Christianity was the most popular religion in the Arabic regions, as well as in non-Arab territories like Persia. Arab philosophers were confronted with the divergent lines of thought represented by Aristotle and the Neo-Platonists. Presented with these two different perspectives, the early Arabic philosophers had to choose one, or the other, or try to harmonize both.
One of the earliest Arabic philosophers was Al-Kindi (who died around the year 870 A.D.). Al-Kindi, like the Islamic philosophers who followed him, sought to harmonize a rational philosophical system with the teachings Islam. His teachers, and the authors of many of the books he studied, were Christians. He wanted the tradition of philosophy to continue under Islamic rule.
He was followed by Al-Farabi, who based his thought primarily on Plato's Laws and Republic. Al-Farabi, who was either a Turk or a Persian, and therefore not an Arab, represents a quite developed system of philosophical terminology; he died around 950 A.D. His teachers were Christians, and therefore he was exposed to Greek philosophy, which was less tolerated in purely Islamic circles. He carefully distinguished between philosophy and theology, and placed philosophy in the service of theology. He introduced formalized logic into the Arabic world, and began producing arguments for the existence of God, which were strikingly similar to Thomistic arguments for the same. Like Aquinas (who was familiar with Al-Farabi's works) and his followers, so Al-Farabi and his followers were often mis-understood in their arguments for the existence of God. Neither the Islamic nor the Thomist philosophers were trying to prove the existence of God, even though they wrote "proofs". Much rather, because both were surrounded by a community of their respective faiths, each group took the existence of God as something which did not need to be proved. Why, then, write such proofs? The "proof for the existence of God" was a literary form for philosophical discourse; by writing such a proof, a philosopher could exhibit his skill, demonstrate the particular kind or argumentation which he thought to be most powerful, and en passant make certain assertions about other issues in philosophy. Thus, many Aristotelian arguments for God (Islamic or Thomist) were written as a way to make assertions about physics and metaphysics. Scholars debate whether he grew up in Turkey or in Persia, but in either case, Al-Farabi's native land still offered him more intellectual freedom at the time, because it was on the fringe of the Islamic region, and not yet as thoroughly dominated by Muslim control.
The high points of Arabic thought began with Avicenna (Abu Ali ibn-Sina), who based himself upon Aristotle, but strove to either further refine or change Aristotle's system in order to harmonize it with some of the teachings of Islam. It is an interpretive question whether Avicenna's work is a natural development of Aristotle's system, and thus represents an internal and organic application of the system to itself, or whether Avicenna subjected the Aristotelian system to the external pressures of Islamic orthodoxy and so introduced additions to the system which were not inherent to the organic whole of the system itself. In either case, Avicenna replaced Aristotle's two-fold basis (matter and form) for metaphysics with a three-fold basis (matter, form, and being). According to Avicenna, God (qua necessary Being) provides the underlying support for the ongoing process of these three constituents; hence, the existence of the world depends on God. Avicenna was deeply influential in the work of Aquinas; Avicenna's impact is evident in the Thomistic doctrine of God as the underlying support for the existence of the world. Avicenna also indicated that the fundamental metaphysical distinction between necessity and contingency was parallel to, and based upon, the distinction between existence and essence. Avicenna's distinction of existence and essence again shows both how he studied Aristotle and how he modified Aristotle's system - cf. Aristotle's distinction between accident and essence. Avicenna has had an influence on the development of modern formal logic, which works with such modalities. Quite notable is his assertion that the mind necessarily apprehends the idea of being, although it is normally acquired through experience; but even without experience, he says, the mind would have this idea: here he is quite ahead of his time, anticipating themes which would occupy modern philosophers. Avicenna distinguished between two kinds of necessity: contingent beings were not necessary of themselves, but necessary as the result of a determining cause; truly necessary beings were necessary of themselves. Avicenna lived from 980 until 1037.
This most productive period of Islamic thought continued with Averroes (ibn-Rushd), who lived from 1126 until 1198. Averroes represented an attempt to return to a purer form of Aristotelianism, in contrast to the modified Aristotelianism of Avicenna. Averroes also marked the beginning of the decline of Arabic philosophy, as Muslim control of cultural life became complete.
The Islamic philosophers of the Middle Ages bore a strong resemblance to their Christian European counterparts, which whom they exchanged information. The era of Arab philosophy came to an end as Islam made further inroads and eventually eliminated the tradition of philosophical reflection.