1. Hoodbhoy’s Conflict Thesis
It has often been argued that the theologian Al-Ghazali played a key role in the decline of science in the medieval period and that this explains the difficulty of incorporating a modern scientific and technological culture in the Middle East today. This story has become so standard that it has been accepted by both the critics of Islamic kalam, as well as kalam theologians themselves, who use it to treat modern science as a contamination that has been shown to be theologically unsound by Al Ghazali. A standard view along these lines is Pervez Hoodbhoy’s Islam and Science: Religious Orthodoxy and the Battle for Rationality 
At the time of Al Ghazali, science was largely represented by Greek science—especially Aristotelian science. Al-Ghazali worked relentlessly to rid Islamic culture from its contamination, as he saw it, by its Hellenistic heritage. Al-Ghazali’s condemnation of the followers of Aristotle was categorical:
Figure 1: Illuminated page from the Kitab Ihya’ ‘Ulum al-Din (Revival of the Religious Sciences), Al-Ghazali’s great masterpiece. Manuscript preserved in Tunisia’s National Library, Tunis. (Source).
“We must therefore reckon as unbelievers both these philosophers themselves and their followers among the Islamic philosophers, such as Ibn Sina, al-Farabi, and others, in transmitting the philosophy of Aristotle .”
It leads Hoodbhoy to conclude:
“The rumblings against the secular and universalistic character of Hellenistic knowledge started… almost from the time of its introduction into the Islamic culture. But the confusion of competing doctrines, lack of familiarity with the techniques of logic and science, and incessant bickering, did not at first allow for a sustained and decisive attack against rationalism. It was not until the theologian Al-Ghazali – a man who Seyyed Hossein Nasr gratefully acknowledges as having ‘saved orthodoxy by depressing science’ – that a coherent rebuttal of rationalist philosophy was attempted. With perspicacity, scholarship, and single mindedness, Al-Ghazali worked tirelessly to rid Islamic culture of the foreign intrusion of Greek thought .”
Hoodbhoy identifies Al-Ghazali’s critique of science as centred on the concept of causality that is “the cornerstone of scientific thinking .” This is because Al-Ghazali assumed that it is false to believe that there are physical laws in nature, because he followed the Asharite belief that God, at every instant, destroys and recreates the universe incessantly. Hence there is no continuity in the universe from one point in time to another. Fire does not cause burning of cotton, say, for the fire at one instant of time near the cotton and the cotton that burns at the next instant are not part of the same universe. One universe had been destroyed and another created in the intervening interval so that there is no continuity between them to allow us to legitimately claim that the fire was the cause of the burning. It is God who is the direct cause of the fire at one instant and the burning at the next that lead us to falsely suppose that one physical event caused another. It leads Al-Ghazali to write:
“This we deny, saying: the agent of the burning is God, through His creating the black in the cotton and the disconnection of its parts, and it is God who made the cotton burn and made its ashes either through the intermediation of the angels or without intermediation. For fire is a dead body which has no action, and what is the proof that it is the agent. Indeed, the philosophers have no other proof than the observation of the occurrence of the burning, when there is contact with fire, but observation proves only a simultaneity, not a causation, and, in reality, there is no cause but God .”
It leads Hoodbhoy to conclude:
“The decline of science in Islamic culture was contemporaneous with the ascendancy of an ossified religiosity, making it harder and harder for secular pursuits to exist. This does not pinpoint the orthodox reaction against science as the single cause. In particular, it does not exclude economic and political factors. But certainly, as the chorus of intolerance and blind fanaticism reached its crescendo, the secular sciences retreated farther and further. Finally, when the Golden Age of the Islamic intellect ended in the 14th century, the towering edifice of Islamic science had been reduced to rubble .”
Hoodbhoy quotes the admonition to young scholars by Al-Ghazali to support his conclusion:
Figure 2: Last page of Al-Ghazali’s autobiography in MS Istanbul, Shehid Ali Pasha 1712, dated 509 H/1115-16 CE. (Source).
“O youth, how many nights have you remained awake repeating science and poring over books and have denied yourself sleep. I do not know what the purpose of it was. If it was attaining worldly ends and securing its vanities and acquiring its dignities and surpassing your contemporaries and such like, woe to you and again woe” .
It is therefore evident that Hoodbhoy represents a fairly dominant view among historians of science who consider that Islamic theology, especially in the version developed by Al-Ghazali, to be essentially in conflict with science. Modern science requires that we explain the world in terms of cause-effect relations and the laws that regulate them. Al Ghazali argued that there are no necessary regularities in the world as the Aristotelians maintained and, therefore, the search for science is a futile quest. Hence, the decline of science that followed after his views came to dominate Islamic theological thinking can be directly attributed to his influence upon Islamic culture.
2. Saliba’s Neutrality Thesis
However, George Saliba, in his recent study Islamic Science and the Making of the European Renaissance , questions the claim that Al-Ghazali caused the decline of science in the Muslim world. He bases his argument on studies which showed that some of the most important developments in scientific thinking within Islamic civilization actually emerged after the lifetime of Al-Ghazali. He writes:
“The conclusion that is usually drawn from the success of Al-Ghazali’s religious thought is that this triumph must have caused the death of its counterpart, the rational scientific thought. Thus in a simple fashion Al-Ghazali was single-handedly held responsible for the decline of rational, read scientific, thought in Islamic civilization in these later centuries… Focussing on the conflict between science and religion before Al-Ghazali’s period may have contributed to the lack of awareness that there were scientists working during that period and whose main concern was to combat the imported Greek scientific tradition, because of the errors and blemishes it harboured, and not because of the religious thought of their time. Muhammad b. Musa’s critique of Ptolemy, or Razi’s ‘Shukuk against Galen’, or even Ibn al-Haitham’s ‘Doubts against Ptolemy’, among many others discussed above, have gained some importance only recently as texts rebelling against the religious authorities of their time” .
This leads Saliba to also argue:
“[T]hose who hold Al-Ghazali responsible for the age of decline will have to explain the production of tens of scientists, almost in every discipline, who continued to produce scientific texts that were in many ways superior to the texts that were produced before the time of Al-Ghazali. In the case of astronomy, one cannot even compare the sophistication of the post-Ghazali texts with the pre-Ghazali ones, for the former were in fact far superior both in theoretical mathematical sophistication, as was demonstrated by Khafri, as well as in blending observational astronomy with theoretical astronomy, as was exhibited by Ibn al-Shatir .”
However, Saliba maintains that Islamic science did not really decline until the discovery of America altered the relative positions of the wealth of civilizations. He writes:
“[I]n my opinion, this age of decline was less caused by such factors as a book of Al-Ghazali… what seems to have happened was the onset of a race between the European royal houses and the rest of the world, including the Islamic world. But no one should forget that the real race started in the sixteenth century as a result of the discovery of the New World, and that it was a race between Europe, on the one hand, and the rest of the world, on the other. The race continues to intensify till this very day. In relative terms then, when one culture begins to produce more and better science, for now it can afford to, the other culture will look like it declined, no matter what.”
Hence, Saliba rejects the notion that Al-Ghazali’s theology caused the decline of science in the Muslim world. It could not have since many of the major developments in Islamic science that made key contributions to modern science by breaking with the ancient Greeks actually developed only after the death of Al-Ghazali. Hence, he adopts what may be labelled as the neutrality thesis — Islamic theology may not have helped science, but it certainly did not hinder its growth in the Islamic world.
3. Al-Ghazali as Nemesis of Hellenistic Science
It is clear that two different notions of the impact of Al-Ghazali on science are offered by Hoodbhoy and Saliba. On the one hand, Hoodbhoy holds him responsible for the decline of science in the Arabic/Islamic civilization. On the other hand, Saliba sees his role as indifferent to science since many of the key developments of Arabic/Islamic science took place after Al-Ghazali’s demise in 1111 CE. These key developments involved new traditions of science that no longer remained subservient to Greek science but broke away from it.
Figure 3: Front cover of The Alchemy of Happiness, by Mohammed Al-Ghazzali, the Mohammedan Philosopher, translated Henry A. Homes (Albany, N.Y.: Munsell, 1873). Transactions of the Albany Institute, vol. VIII. Digital version. See another digital publication edition: The Alchemy of Happiness by Al-Ghazzali, translated by Claud Field, 1909.
How could such different views emerge concerning Al-Ghazali’s impact upon science? How could Al-Ghazali be seen as destroying science and yet also science be seen as progressing to even greater heights after Al-Ghazali, within the civilization during the time his influence was growing? Is it possible that Hoodbhoy and Saliba are speaking of the same tradition of science? Indeed we will find that Al-Ghazali’s critique was essentially directed at the Greek tradition of science — especially the Aristotelian tradition — and that the science that grew after Al-Ghazali, which Saliba appeals to in order to reject the charge that Al-Ghazali caused the decline of science in the Muslim world, essentially broke free from the Greek heritage. Hence, there need be no incompatibility between the views of Hoodbhoy and Saliba since Al-Ghazali may have had a negative impact on the Greek heritage of science, but no such adverse influence on a different non-Greek tradition of science. However, neither Hoodbhoy nor Saliba seem to have entertained such a nuanced position.
Indeed, we will find that such a more refined understanding is quite illuminating. First, it explains why many are led to think that Al-Ghazali was vehemently opposed to science since he opposed the notion of science which dominated thought during his lifetime — namely the science embraced by the followers of Aristotle. He argued against Aristotelian science and its notion of cause-effect relations in the world. Moreover, since he offered no alternative framework for science it is easy to see him as having a negative impact upon science in the Arabic world.
However, his opposition to Aristotelian science also raises the following question: Would Al-¬Ghazali be opposed to the modern conception of science? After all modem science emerged with Bacon, Descartes, Galileo, Kepler, and Newton in vehement opposition to Aristotelian science. Of course, Al-Ghazali did not know modern science — it developed after his lifetime in another cultural arena. But in order to decide whether Al-Ghazali caused the demise of science per se, it is crucial to determine whether the reasons Al-Ghazali gave for opposing Aristotelian science are also applicable to modern science. If such were not the case, then al-Ghazali cannot be charged with subverting science per se, but only the Aristotelian conception of science.
Indeed a closer examination of Al-Ghazali’s views show that what he objected against was the particular kind of cause-effect relationship which under-girded Aristotelian philosophy and science. This assumed that the link between a cause ‘A’ and its effect ‘B’ was a necessary linkage, and that the goal of science was to establish such necessary cause-effect connections. But Al-Ghazali recoiled at the notion of causal necessity because it seemed to place limits on the omnipotence of God. It implies that when God created the universe He could not have made it differently — i.e. He could not have made it a world where the cause ‘A’ did not give rise to the effect ‘B’ since ‘B’ necessarily follows from ‘A’.
Figure 4: A leaf from Ihya’ ‘Ulum al-Din. Manuscript in naskh script from Eastern Anatolia or Iran, circa 14th century. Part of the celebrated treatise on the Muslim faith and Sufi life, Arabic manuscript on buff paper, 104 folios in naskh script, titles in large size, minor headings in red, very good condition. (Source).
In his influential work, The Incoherence of the Philosophers, Al-Ghazali writes:
“According to us the connection between what is actually believed to be a cause and what is believed to be an effect is not a necessary connection, each of the two things has its own individuality and is not the other, and neither the affirmation nor the negation, neither the existence nor the non-existence of the one is implied in the affirmation, negation, existence. and non-existence of the other — e.g. the satisfaction of thirst does not imply drinking nor satiety eating, nor burning contact with fire, nor light sunrise, nor decapitation death, nor recovery the drinking of medicine, nor evacuation the taking of a purgative and so on for all the empirical connections existing in medicine, astronomy, the sciences and the crafts. For the connections in these things are based on a prior power of God to create them in a successive order, though not because this connection is necessary in itself and cannot be disjoined — on the contrary, it is in God’s power to create satiety without eating and decapitation without death and so on with respect to all connections. The philosophers however deny this possibility and claim that that is impossible. To investigate all these innumerable connections would take too long, and so we shall choose one single example, namely the burning of cotton through contact with fire; for we regard it as possible that the contact might occur without the burning taking place, and also that cotton might be changed into ashes without any contact with fire, although the philosophers (Aristotelians) deny this” .
In this passage, Al-Ghazali develops a powerful attack on the Greek conception of science by arguing — as Hume was to do much later — that there is no necessary link between an event we take to be a cause and another we take to be its effect. The attack is all the more telling because Greek science had assumed that possessing knowledge of the nature of something ‘A’ – what can be termed the essence of ‘A’ – would enable us to logically deduce what its effect would be. Moreover, Aristotelians had also presupposed a four-fold order of causes for any effect — what they termed material, formal, efficient and final causes. To explain an effect was to show how it necessarily followed from these four causes. However, by demonstrating that such a necessary connection is not demonstrable since God could have created another universe in which the same set of causes could have led to a different effect from the one actually observed, Al¬-Ghazali subverted the epistemological basis of Aristotelian — i.e. Greco-Arabic – science of his time. Knowing the essence of a thing cannot explain its effect since the same essence could, in principle, have led to a different effect. Reason cannot reveal what effect would arise from a known cause.
However, Greek science demanded that we explain an effect only by showing how it rationally followed from its cause even if Platonists and Aristotelians differed as to how such a rational link gets discovered. For Plato reason has not only involved a deductive method that produces new knowledge by inference from well-established first principles, but also a dialectical method to establish with certainty the first principles of any science. Hence, by deploying dialectical and deductive reason Platonists not only gave an approach to arrive with certainty at first principles, but also proceed to infer other equally certain principles by deduction. In contrast to Platonic rationalism, Aristotle stressed that experience of actual phenomena is a prerequisite to apprehending the first principles of a science. However, once we arrive at knowledge of such principles we can also come to recognize them as self-evident. The difference between the Aristotelian and Platonic views can be explained as follows. Plato saw things in the world as imperfectly embodying ideal forms that could be apprehended only by the intellect. For Aristotle the forms did not exist in a transcendental realm, but only in particular objects. Hence, they could only be known by direct observation. This implies that the first principles of a science can only be apprehended by perception and not reason. However, Aristotle agreed with Plato that the first principles cannot possibly be false since they could be apprehended as self-evident once we arrived at knowledge of them through direct experience.
Figure 5: Page from the manuscript of the Ihya’, vol. 3: Kitab al-Raja’ wa-‘l-Khawf (The Book of Fear and Hope). MS in Arabic on vellum, Morocco, 1350, 17 folios in Maghribi script of Fasi style, with royal Marinid waqf inscription. (Source).
Al-Ghazali’s argument against the notion of self-evident first principles is the following. He agrees that in order to deduce cause-effect relations we need to begin with some principles that can function as the premises of the argument. But these principles can be either discovered by reason as Plato held, or experience as Aristotle maintained. Let us also assume that either reason or experience (or both) make it possible to establish these principles as self-evident — i.e. certain and indubitable. We can then use them to predict cause-effect connections by making deductions on their basis. Hence, since the principles we start with could not be otherwise, being self-evident, and the cause-erect relations could not be otherwise, being deductively connected by logic, we have established that the cause-effect relations are necessary in every conceivable universe. God could not have created a universe where these causal necessities would be violated. By thus setting limits on the Will of God, they impugn the omnipotence of God. Hence, argues Al-Ghazali, since God is omnipotent there cannot be self-¬evident first principles for a science. Since indubitableness of the first principles is the cornerstone of Greco-Arabic science, Al-Ghazali’s argument attacks the foundations of the established scientific tradition of his time.
In place of the notion of self-evidence as the basis of for cause-effect linkages Al-Ghazali introduces a different idea. He argues that when we observe an event ‘A’ to be regularly connected with another event ‘B’ as its effect, it is not because of any necessary link between ‘A’ and ‘B’, but because it has been so willed by God. The regularities we find in causal relations are, according to Al-Ghazali, “The Habits of God”.
One important motivation for Al-Ghazali’s critique of the Greek conception of science is to counter the argument that the miracles described in the Quran are impossible because they violate the necessary cause-effect relations in nature. This can be illustrated by considering the example of fire causing cotton to burn. If the burning is necessary once the cause — cotton contacting fire — takes place then not even God could have stopped it. But if the burning is simply the outcome of the habits of God, who regularly ensure that cotton burns whenever made to contact fire, then a miracle would occur when God suspends this habit and cotton ceases to burn even in contact with fire. Miracles can then be said to occur whenever God, in order to vouch for the authenticity of a prophet, suspends His habit, and the expected effect does not occur.
Hence Al-Ghazali’s theological motivations lead him to argue against the conception that the causal regularities we see in the world are logically necessary relations. Clearly his views are subversive of Greek science which holds these regularities to follow from self-evident first principles. But are they also subversive of modern science? If this is not the case it puts into question the notion proposed by Hoodbhoy that Al-Ghazali subverted science per se simply because he undermined the belief in Greek science. It also suggests that Saliba may be right in claiming that Al-Ghazali had no impact in slowing down the progress of science in the Muslim world — especially those traditions of science that sundered the Arabic heritage from its Greek predecessor.
4. Al-Ghazali and Modern Science
In order to appreciate how Al-Ghazali’s view of causality impinges on the modern conception of science, consider Isaac Newton’s formulation of how the universe came to possess the properties and causal regularities we find in it:
Figure 6: Front cover of Al-Ghazali’s book Letter to a Disciple, translated by Tobias Mayer. The Islamic Texts Society, 2005.
“… it seems probably to me that God in the beginning fanned matter in solid, massy, hard, impenetrable, moveable particles of such sizes and figures and with such other properties and in such proportion to space, as most conduced to the End for which He formed them… And therefore, that Nature may be lasting, the changes of corporeal things are to be placed only in the various separations and new associations and motions of these permanent particles… it seems to me farther, that these particles have not only a ‘vis inertia’ [inertial force], accompanied with such passive laws of motion as naturally result from that force, but also that they are moved by certain active principles, such as that of gravity, and that which causes chemical fermentation and the cohesion of bodies .”
Indeed it is possible to see the Newtonian view as lending support to Al-Ghazali’s critique of Greek science. Newton clearly relinquishes the Aristotelian conception of cause-effect relations as necessary, and assumes Al-Ghazalian view that they are contingently dependent on God’s Will. However, in contrast to Al-Ghazali, Newton explicitly recognizes that the laws of nature are not simply sustained by God as habits, though God could suspend them if he wished, but are commands upon nature laid down by God. These commands are what generate the correlations between causes and effects we find in nature. Hence, God as the primary cause produces effects in the world through secondary causes that are also the result of God’s action. Hence the Newtonian view contrasts with Al-Ghazalian position in making a distinction between primary and secondary causes – a distinction that Al-Ghazali does not invoke since for him God directly intervenes to produce every effect in the world.
There are good grounds to assume that the Newtonian view itself is the outcome of the response of Scholastic philosophers in Europe to Al-Ghazali’s conception of causality. Thomas Aquinas introduced the notion of secondary causes as mediators between God as primary cause and the effects we observe in nature in order to accommodate both Aristotelian science and Al-Ghazali’s critique of the epistemology of Greek science. Aquinas’ account acknowledges Al-Ghazali’s demand that God could have made the world otherwise by making it subject to a different set of regularities, but also accommodates the Aristotelian view that the cause effect relations are subject to well-defined regularities. It does this by preserving the concept of regularities in nature, but rejecting the notion that such regularities are necessary or self-evident principles. This intermediate position of Aquinas acknowledges that the doctrine of creation out of nothing, which affirms the dependence of all beings upon God as its primary cause, is not inconsistent with the discovery of secondary causes in nature .
After the collapse of Aristotelian philosophy in the 17th century, the distinction between primary and secondary qualities served to reconcile the mechanical conception of nature with religious beliefs for many of the thinkers who pioneered the Scientific Revolution. It is also noteworthy that when David Hume studies the problem of causality in the 18th century, he too came to argue that there is no necessary connection between a cause and its effect. He even went further. He maintained that only custom and habit lead us to treat the causal nexus as necessary. This is interesting because both Hume and Al-Ghazali reject the conception of necessity by treating it as an illusion created by custom and habit — that of God or humans. But what is significant is that in both cases the regularities of the cause-effect linkages are seen as contingent — they could have been otherwise. Being contingent, the only way we can discover and justify what they are is by appeal to empirical data. The idea of self-evident first principles so integral to Greek science is thereby rejected.
This raises the question of the extent to which the views of Hume were influenced by Al-Ghazali. Historian of science, Osman Bakar, argues that the influence could be much greater than is often supposed because not only Hume’s arguments, but also his exemplars, have striking parallels in Al-Ghazali’s writings.
Figure 7: Manuscript of The Alchemy of Happiness, Farsi copy held in the Bibliothèque Nationale de France in Paris. From Iran, 1308. (Source).
“Interestingly enough, in his repudiation of causality, Hume presented arguments very similar to those offered by the Asharites, but without positing the Divine Will as the nexus between two phenomena which the mind conceives as cause and effect. Moreover, some of his examples were the same as those of the Asharites. This led certain scholars to assume that Hume must have been acquainted with Asharite atomism through the Latin translations of Averroes’ “Tahafut al-Tahafut” (The Incoherence of the Incoherence) and the above mentioned work of Maimonides [The Guide to the Perplexed] .
In the discussion above, we have considered the relationship between Islamic theology and science — especially by looking at the work of Al-Ghazali whose status in Sunni Islam parallels that of Shankara in the Hindu world and Chu Hsi in the Chinese world. It is often supposed that Al-Ghazali demolished the basis for science in the Muslim world by both his theological followers and his scientific dissidents. Hoodbhoy represents the view of many scientists who bemoan the negative impact of Al-Ghazali on science, and blame the lack of development of science in large sectors of the Muslim world on his influence. Religious fundamentalists celebrate his achievement in saving orthodoxy by depressing science, and take it as one further argument for resisting the intrusive ideas of modern science.
However, we have seen there are good grounds for questioning such views on both historical and epistemological grounds. Historically, Saliba has argued that science advanced in the Muslim world even after Al-Ghazali — especially in directions that broke free from the heritage of Greek science. Even if he thinks that this shows Al-Ghazali’s view did not have a negative impact on science in the Muslim world, it also raises the question of whether Al-Ghazali had a positive impact on scientific developments in the Muslim world after his time.
There are reasons to suppose that Al-Ghazali’s impact may indeed have been positive in this sense. It gave strong epistemological and theological grounds for breaking free from the rationalist straitjacket of Greek science. It therefore liberated thought in new directions within the Muslim world. His impact on the Western world can also be seen as liberating in that Scholastic philosophy, in response to problems he posed, developed new ideas that separated secondary and primary causes and paved the way for a science able to see that first principles of knowledge cannot be rationally adjudged to be self-evident, but are always contingent.
This laid the basis for modern empirical science.
Figure 8: Page from the Munqidh manuscript by Al-Ghazali (Suleymaniye Library: Sehid Ali Pasa No. 1712/2). (Source).