4.3.4 Islamic Philosophy

The rise of Islam is linked to the decline of the Roman and Persian Empires. More specifically, the ruinous wars that the two once-great powers fought left both weak. In 622 CE, the Prophet Muhammed led his followers out of Mecca to Medina, which signaled the birth of Islam as a political power (Adamson 2016, 20). In the early years of Islam, theologians prohibited the teaching of Aristotle and other Greek philosophers on the grounds that they were contrary to the true Muslim faith. This restriction began to give way in the eighth century CE, which led to the flourishing of philosophy in the Islamic world.

As the Roman Empire declined, the Muslim world safeguarded ancient philosophical Greek and Latin texts through major centers of learning in Alexandria, Baghdad, and Cordova. Islamic philosophers published major works in metaphysics, epistemology, and natural philosophy. Key Islamic scholars who carried classical philosophy forward include Ibn Sina (whose Latin name became Avicenna), Ibn Rushd (whose name was Latinized to Averroes), and Al-Gazali. Of these three, Ibn Sina is the linchpin of Muslim philosophy. His genius inaugurates the shift from an early period focused on the consolidation of Greek learning to a later period of philosophical and scientific innovation (Adamson 2016).

Ibn Sina (Avicenna)

Abū-ʿAlī al-Ḥusayn ibn-ʿAbdallāh Ibn-Sīnā (c. 970–1037 CE) was a Persian polymath who published works in philosophy, medicine, astronomy, alchemy, geography, mathematics, Islamic theology, and even poetry. Because of the vast scope of Ibn Sina’s intellectual endeavors, he is considered the linchpin between Islamic philosophy’s formative phase and its more creative phase during the Golden Age of Islam, which extends from roughly the 8th through the 13th centuries. During this period, Islamic culture and learning flourished, and the Muslim-ruled lands spread from the Middle East, through Northern Africa, and into the Iberian Peninsula. Taking his cue from Aristotle, Ibn Sina sought to present a complete philosophy that would address both theoretical and practical philosophy. Some have estimated that Ibn Sina published as many as 450 works, though others place the figure at under 100 (Namazi 2001).

Ibn Sina’s work was highly influential within both the Muslim and the Christian world. His proof of the existence of God became predominant. Called the Proof of the Truthful, the argument proposed that existence requires that there be a necessary entity—an entity that cannot not exist. Elements of the material world—animals, plants, rivers, mountains—are contingent—that is, they come and go. They may have existed in the past but do not exist now, or they may exist now but will not exist in the future. Therefore, they can not exist. Therefore, there must be a nonmaterial entity that causes this material world to come into existence.

Much like Aristotle, Ibn Sina believed that the rational order of the universe was comprehensible by our human minds, and his well-ordered and complete philosophical project demonstrated this (Gutas 2016). Ibn Sina’s most influential book is the Canon, a five-volume medical encyclopedia that—translated into Latin and Hebrew—became the textbook for the study of medicine in European universities from the 12th to the 17th century (Amr and Tbakhi 2007). Ibn Sina’s epistemology—and in particular, his development of an empiricism that advances far beyond the Epicureans and is, in fact, comparable to that of John Locke—has received less attention.

Ibn Sina, similar to Locke, proposed that humans are born with a rational soul that is a blank slate. The child possesses the five external senses associated with the animal soul (sight, smell, sound, taste, and touch) and two internal senses of the human rational soul, memory and imagination. The child gathers and stores information from the senses and is able to abstract intelligible concepts about the world from this sensual data and about the human soul (rationality) through reflection (which Locke later calls experience). So, a child in a high chair might drop food and observe that it falls to the floor, based on experience, but a child through reflection also observes a causal relationship. For Ibn Sina, gravity exists both in the materialist realm of the senses and in the cognitive realm of the mind or soul. Like gravity, numbers exist in both realms, the abstract concept of the number two and concrete pairs of objects, such as two shoes or two apples. He explains in The Metaphysics of Healing, “Number has an existence in things and an existence in the soul” (quoted in Tahiri 2016, 41).

The child’s mind organizes this information—making generalizations, separating out the essential from the nonessential, and affirming or negating relationships. Through this process, the child forms definitions and propositions that reflect the logical and mathematical modes of rational thought (Gutas 2012).

Ibn Sina stated that all knowledge is a result either of forming concepts or acknowledging the truth of propositions. He distinguished different types of propositions, each of which have different sources and therefore different ways to prove or disprove the proposition. Table 4.2 lists 5 of Ibn Sina’s 16 types of propositions and examples (Gutas 2012).

Some types of propositions, such as sense data and data based on reflection, are knowledge based on the external or internal senses. Tested data, however, can be accepted as true only after repeated observation and attribution to a cause. For example, “fire causes burns” would be based on the observations that fire is hot, hot things burn objects (cause), and flesh is an object. The truth of data provided by multiple reports can only be confirmed if it has been reported by so many sources that it is highly unlikely to be a falsehood.

Building on Aristotle’s idea of induction conveyed in Posterior Analytics, Ibn Sina developed a scientific methodology of experimentation in his treatise “On Demonstration” within his Book of Healing. Induction involves making an inference based on observations. Ibn Sina stated that—unlike untested induction—experimentation provides the basis of certain knowledge. He used the example of the relationship between consuming the plant scammony and purging (vomiting). He noted that the observation of a positive correlation does not prove that the relationship exists but rather that the lack of observation of a negative correlation (cases in which scammony did not cause purging) provides stronger evidence. Ibn Sina’s experimentation involved a search for falsification of a correlation—just like the scientific method used today, which, for example incorporates control groups (McGinnis 2003). Furthermore, Ibn Sina insisted that a causal term be inserted into the relationship that is observed. It is not scammony that causes purging but a property that scammony has that requires further investigation. So Ibn Sina’s argument is (1) scammony has the power to purge, (2) scammony causes purging, (3) a power to purge causes purging. Exactly what the power to purge is remains uncertain until further investigation. In the first example above, the cause is established: (1) fire burns flesh, (2) fire is hot, (3) heat burns flesh.

As advancement of experimental knowledge challenged Islamic theology, debate emerged over how to reconcile faith and science.

Ibn Rushd (Averroes)

Ibn Rushd (1126–1198), known as Averroes in the Latin world, was born into a family of jurists in Cordova in Andalusia, or Muslim-ruled Spain. Like Ibn Sina, his philosophy took its inspiration from Aristotle. Like Ibn Sina and Aristotle, his work ranged across a number of domains, from metaphysics and logic through medicine and natural philosophy. Much of this work took the form of commentaries on Aristotle. He thought that the Neoplatonic interpretation of Aristotle had distorted the original meaning of Aristotle’s work and sought a return to Aristotle’s original works in his commentaries. Ibn Rushd was pivotal to the revival of Aristotle in Europe. The tradition of commentary on Aristotle’s works that developed among Islamic philosophers developed Aristotle’s thought in fascinating ways and kept Aristotle scholarship alive.

Ibn Rushd saw demonstration as the key to logic and the condition for philosophical certainty and scientific reasoning (Ben Ahmed and Pasnau 2021). This had important theological implications and led to confrontations with theologians who believed that philosophical reflection was at odds with the Muslim faith. He sought to demonstrate the existence of God by showing that his creation was fine-tuned for humans in a way that could not be simply a matter of chance. In addition, he advanced an argument, taken up today by intelligent design advocates, that holds that it is not possible to explain the complexity of living beings without a creator.

Even as philosophy gained ground in the Islamic world, theological traditionalists remained influential. These traditionalists denied that reason could bring one closer to God. Ibn Rushd was among a number of philosophers who opposed this traditionalism and sought to show the compatibility of faith and reason. Not only did Ibn Rushd seek to show that reason was compatible with faith, he went further and cited Quranic scripture to show that religion required philosophical reflection. He wrote, “Many Quranic verses, such as ‘Reflect, you have a vision’ (59.2) and ‘they give thought to the creation of heaven and earth’ (3:191), command human intellectual reflection upon God and his creation” (quoted in Hiller 2016).

Al-Ghazali, The Incoherence of the Philosophers

Al-Ghazali (c.1056–1111) was one of the most prominent Sunni Muslim theologians and philosophers. Writing in a period after the initial establishment of the Sunni sect, he sought to refute various challenges to its teachings from both Shi’ite religious scholars and philosophers. In his most well-known work, The Incoherence of the Philosophers, Al-Ghazali sought to refute these challenges while also strengthening the theological basis for Sunnism. Ibn Rushd wrote a refutation of Al-Ghazali’s The Incoherence of the Philosophers. In it, he argues against Al-Ghazali’s claim that philosophical reflection must remain distinct from the Muslim faith and that mystical union with Allah or God is the only true path to religious enlightenment. This dispute between Al-Ghazali and Ibn Rushd represents the conflict between faith and reason that characterized medieval Islam. This same conflict remains relevant in the present.