In the series of extracts I’m running from my still-being-written book on the history of moral thought, I have reached Chapter 8, which explores the struggle between the Rationalists and the Traditionalists in early Islam, and the significance of that struggle not just to Islam but to Christianity and to the development of modern secularism too.

The expansion of the Islamic empire from India to Iberia created new political tensions and theological dilemmas. It also created new kinds of administrative problems, the most pressing being the practical question of how to collect taxes, keep accounts and maintain records of state in an empire consisting of dozens of languages, forms of law and administrative styles.  In the early eighth century Caliphs decided that Arabic should be the common language of empire, and the one in which public records and accounts were to be kept.  So there began what came to be called the translation movement – a huge project sponsored by caliphs, local governors and rich philanthropists to translate local records into Arabic.  Soon the translation movement spread its wings. The new empire had within its borders a treasure house of philosophical, scientific and religious texts, mainly Greek and Persian. Translators began first with those works that helped meet the pragmatic needs of the new rulers – works on subjects such as medicine, natural history, astronomy and astrology. Over time, intellectual horizons broadened further still. Translators moved from works of practical learning to more speculative philosophy. The Arab world discovered Plato and Aristotle.

The acquisition by Arabs of the philosophical jewels of the Greek and Persian worlds helped transform the intellectual culture of the new empire. In the mid-eighth century the Caliph al-Mansur built the new city of Baghdad to be his imperial capital.  And here his great grandson, the Caliph Al-Ma’mun, created the ‘House of Wisdom’, a celebrated library and centre for scholarship that helped turn Baghdad into the world’s greatest intellectual centre of its time, the Athens of its age.

As Christian Europe endured the so called ‘Dark Ages’ between the extinguishing of the final sparks of Hellenism in the fifth century and the re-ignition of cultural life in the Renaissance almost a millennium later, an intellectual tradition flowered in the Islamic world as lustrous as that of Ancient Athens before or Renaissance Florence after. Centred first in Baghdad and then in Cordoba, in Muslim Iberia, Arab philosophy and science played a critical role not just in preserving the gains of the Greeks but in genuinely expanding the boundaries of knowledge. It also laid the foundations for the European Renaissance and the Scientific Revolution. Neither happened in the Muslim world. But without the Muslim world, neither may have happened.

By the second half of the tenth century, the translation movement had come to an end largely because all the great works had already been translated and studied.  By now a new movement had begun – that of original Arabic scholarship. Over the next three centuries there was in the Muslim world a remarkable flourishing of science and learning. Arab scholars revolutionized astronomy, invented algebra, helped develop the modern decimal number system (a rudimentary version of which they had discovered in India), established the basis of optics, and set the ground rules of cryptography.

The translation into Arabic of Aristotle, Plato and other Greek philosophers not only transformed Islamic intellectual culture and theological debate, it also created a fissure that was to run throughout Islamic intellectual history. On the one side of that fissure stood the Rationalists, dedicated to the ideal of falsafah, by which they meant not simply the discipline of philosophy, but also a way of living rationally in accordance with the laws of the cosmos. The faylasufs saw learning as an ethical duty, in much the same way as Enlightenment philosophes (who were deeply indebted to Muslim Rationalists) were to do 700 years later. They took from the Greeks not just their spirit of rational inquiry but also their faith in the boundless power of human intellect and its ability to derive the ultimate truths through reason alone. Most were deeply pious, and accepted the Qur’an as the word of God. But they challenged the idea that religious truths could be accessed only through divine revelation, insisting that reason alone would suffice. Most faylasufs insisted, too, that all theological arguments must adhere to the principles of rational thought. Even the interpretation of the Qur’an and the Sunna were, in Rationalist eyes, subordinate to human reason.

On the other side of the divide were the Traditionalists who viewed human reason as weak and corrupt as human beings themselves, and for whom Revelation and Scripture was the only sure path to truth.  Traditionalists were often forced to engage with rationalists on philosophical ground, and appropriated many arguments from the Ancient philosophers. Perhaps the greatest of all Traditionalist philosophers, Abu Hamid Muhammad ibn Ghazzali, or Al-Ghazzali, (1058-1111), used the method of falsafah to attack its content, attempting to show rationally the incoherence of the Rationalist arguments. But more often than not Traditionalists dissociated themselves completely from falsafah on the grounds that it was either impious or foreign, or both. ‘We should not be ashamed to acknowledge truth and to assimilate it from whatever source it comes to us, even if it is brought to us by former generations and foreign peoples’, insisted Yaqub ibn Ishaq al-Kindi (d c 870), acknowledged as the first Muslim philosopher. It was precisely such openness that the Traditionalists so feared and detested.

The earliest of the rationalist movements was the Mu’tazilite.  Founded by the theologian and jurist Wasil ibn Ata (c 700-748), it flourished mainly in Baghdad and Basra, but its influence was far-reaching. At its heart was a revolutionary defence both of human reason and of the rationality of God’s ways. Since God was entirely rational, so his laws could be substantiated intellectually without necessarily either leaning upon or repudiating the authority of Scripture.

The early insights of the Mu’tazilah were continually developed in the Rationalist tradition through a line of philosophers beginning with al-Kindi, continuing with Al-Farabi (c 872-951), often regarded as the founder of the falsafah school and known as the ‘Second Master’ (second, that is, after Aristotle), and culminating in the work of the two most important Muslim philosophers, Ibn Sina and Ibn Rushd, known respectively in the West as Avicenna and Averroes. This tradition of Muslim Rationalism is today barely remembered in the West. Yet its importance and influence, not least on so-called ‘Judeo-Christian’ tradition, is difficult to overstate.

Abu Nasr Muhammad ibn Farabi (c. 872-951), was a polymath who, aside from making advances in areas as diverse as cosmology, psychology, philosophy, logic, politics, and music, helped establish the Neoplatonist tradition in Islam, marrying the logical rigour and empiricism of Aristotle with the mysticism of Plato and Plotinus, and weaving both into Islamic theology.

If Al-Farabi was the founder of Islamic Neoplatonism, Abu Ali al-Husayn Ibn Sina (980-1037) was its greatest exponent. A Persian born near Bukhara, in what is now Uzbekistan, into a family of Shia officials, Ibn Sina was, like Al-Farabi, a polymath. He is said to have mastered logic, mathematics, physics and medicine by his teens. He read Aristotle’s Metaphysics forty times without understanding it, he tells us in his autobiography, before finally stumbling across Al-Farabi’s commentary on the work, which at once illuminated it for him.  He was a practicing doctor by the age of 16 – and one in much demand in the courts of caliphs and sultans.  His monumental al-Qunun al-Tibb  (Canon of Medicine) interweaves his own observations with a summary of classical clinical learning; it was still used by doctors in Europe as a practical textbook in the seventeenth century.

Ibn Sina wrote more than 400 works, probably the most important and influential of which was Kitab al-Shifa, or Book of Healing. A philosophical encyclopaedia, it is divided into four parts that deal with logic, physics, mathematics and metaphysics. Ibn Sina summarizes here the rational argument about God and faith, making a case not just for the existence of God but also for  Islamic social and ethical practices. He does so, however, with barely a mention of the Qur’an. Rather he stands his argument unaided upon reason.

Abu l-Walid Muhammad bin Ahmad ibn Rushd, or Ibn Rushd, (1126-1196), was the greatest Muslim interpreter of Aristotle and the Muslim philosopher with the greatest influence upon the non-Muslim world. He was born in Cordoba, in al-Andalus, into a family of distinguished scholars and jurists. Working at a time when the Rationalists were already on the defensive in the Muslim world, Ibn Rushd came to wield far more influence within Judaism and Christianity than within Islam. It was through Ibn Rushd that West European philosophers rediscovered their Aristotle, and his commentaries shaped the thinking of a galaxy of thinkers from Maimonides to Thomas Aquinas. In The Divine Comedy Dante places him with the great pagan philosophers whose spirits dwell not in Hell but in Limbo ‘the place that favor owes to fame’. And Raphael, as we have seen, depicts him with Aristotle, Plato and Socrates in his painting The School of Athens. Modern thinkers have described him as a ‘founding father of secular thought in Western Europe’, and even as ‘one of the spiritual fathers of Europe.’

The starting point for most of the Rationalists was God’s truth as revealed to Muhammad. But the stress they placed upon reason raised questions about the very nature of, and indeed need for, Revelation.  A coherent account of the universe, the Rationalists insisted, required a God, an Unmoved Mover that was the cause of all matter and motion but was itself uncaused, a being that by definition had to be outside of space and time for He was the cause of space and time. The Rationalist God was an all-powerful, all-knowing, completely good being, wholly simple in the sense that He possessed no parts, no body, no physical existence. He was immutable, unchangeable, necessary, a God modelled both on Aristotle’s Prime Mover and on Plotinius’ concept of the One that transcends thought and being altogether. This God was not unlike the Allah imagined by most Muslims. But the implications the Rationalists drew from the nature of God were distinct and revolutionary.

As pure being, God was not like any created matter, nor like a human person. As an expression of perfect unity, He was not divided in any way.  He had no brain through which to think, no soul through which to express Himself, no limbs through which to act, no vocal cords through which to speak. Hence, for the Rationalists, God possessed no attributes, either in terms of physical form, such as a body or a face, or in terms of more abstract qualities of mind or character such as wisdom or will. Physical forms, such as bodies, and qualities such wisdom and justice, were, the Rationalists suggested, simply human ways of thinking. Humans possessed no language through which to describe God as a Being-in-Himself. In Plato’s dialogue Parmenides, the old Presocratic philosopher points out to Socrates that to imagine a transcendental realm is to imagine a realm of which humans can have no understanding. And ‘just as we know nothing of the divine by our knowledge’, Parmenides suggested, ‘so they in turn are, for the same reason, neither our masters nor, being gods, do they know human affairs.’

Few Rationalists would have gone as far as Parmenides. Reason led them to see the necessity for God. But reason also led them to insist that it was impossible rationally to define God, and to deny that God could intervene in the mundane aspects of human affairs. A simple being, outside of time and space, and without physical or metal attributes, could not act upon space and time.  God, Ibn Sina suggested, is far too exalted to partake in the humdrum reality of human life. He is the condition of being of the cosmos, and He apprehends everything that has emanated from him and that he has brought into being. But He knows the human world only in general and universal terms. God did not deal in particulars. Nor can humans cannot talk positively of God, only negatively. They can only define what God is not – He is not human, He is not material, He does not consist of parts – not describe what He is.

Both the idea of a simple God, and that of the via negativa – the insistence that it was not possible to speak positively of God – became highly influential, not just in Islam, but in Judaism and Christianity too. But Muslim Traditionalists were aghast. They accepted the simplicity, purity and unity of God. They could not, however, imagine Allah as possessing no attributes or as unable to intervene in every aspect of human life. The Qur’an describes a God that walks, talks, wills and judges, a God that possesses bodily parts (‘But the face of thy Lord shall abide resplendent with majesty and glory’) and sits upon a throne (Allah ‘mounted his throne and imposed laws on the sun and moon’). How could a being outside of time and space, completely unified and possessing no parts also have a face, a body, sit on a throne and be wise and judicious? The Traditionalists’ answer was to shrug their shoulders. ‘Bila kayfa’, they said – ‘Don’t ask how’.

For the Rationalists such an answer was incoherent and unacceptable. In making God so transcendent, pure and good that He could only be spoken of in the negative, however, and in insisting that God was reason itself, the Rationalists paradoxically both diminished the status of God and exalted that of humans. Human reason had to be powerful enough to divine God’s message and human will had to be strong enough to act upon it.

For the Rationalists, divine justice had to be as pure as God Himself. God could do no evil. The Traditionalists accepted that God alone defined good and evil. That which God had decided to be good or evil may sometimes seem arbitrary or unjust but it is not for humans to question. Bila kayfa. The Rationalists, on the other hand, insisted that God could not do that which was contrary to reason or act with disregard for the welfare of His creatures. No omnipotent deity could act in violation of the precepts of justice and righteousness by, say, torturing the innocent, or demanding the impossible, simply because He was God. Good and evil were not arbitrary demands but rational categories that could be established through unaided reason.

This debate returns us to the dilemma that Plato raised in Euthyphro.  Either goodness is divinely defined but arbitrary, or it is rational but exists independently of the gods. The Traditionalists were happy to accept the seeming arbitrariness of God’s commands so long as believers unquestioningly accepted those commands as divine law. The Rationalists could not accept the idea of God making irrational moral demands. But this, as Plato recognized, was to question the very belief that God defined goodness and badness.  Or, to put it another way the idea of a rational morality and that of a rational God came to pull Rationalists in two different directions.