How Muslim Society Rejected Greek Rationalism Roughly 200 Years After Learning it from the Persian Empire

Last Updated on May 6, 2022 by Shaun Snapp

Executive Summary

  • Muslims accessed Greek rationalism first from their conquest of the Sassanid Persian empire.
  • Greek rationalism conflicted with Islam, and within 200 years, it had been rejected and its adherents persecuted.


Muslims accessed Greek rationalism first from their conquest of the Sassanid Persian empire.

Greek rationalism conflicted with Islam, and within 200 years, it had been rejected and its adherents persecuted.

Much is made of the decline of the Islamic Golden Age of Discovery. This article covers the rejection of Greek or Hellenistic rationality that would have made the decline discoveries emanating from the Muslim controlled world predictable.

See our references for this article and related articles at this link.

Obtaining Greek Knowledge from The Persian Sassanid Empire

The Muslim Umayyad Caliphate turned their attention to conquering the Persian Sassanid Empire immediately after conquering Arabia. This was an 18-year process went spanning from 633 until 651. It is generally agreed that Hellenistic ideas never penetrated Arabia prior to this time. Therefore, this is most likely the first time Muslims would have come into contact with Hellenistic intellectual property, as the Persians had the Greek texts and had studied them for many years.

Dating How Long This Knowledge Influenced the Umayyad and Abbasid Caliphates

The influence of Greek knowledge on these caliphates can be said to have followed a U-shaped curve.

In the beginning, the Muslims thought that they could learn nothing from the infidel, as this has and currently is so strongly embedded into Islamic teachings. The high point of the acceptance of Greek knowledge was around 825, so 75 years after the Umayyad caliphate became aware of these texts they captured from the Sassanid Persians. The Mu’tazilites persecuted those who would disagree with rationalism. But the rational cause and effect model of the Greeks was influential in Muslim thought (among the educated elites) for only a short period of time. Soon after the Ash’arites gained the upper hand, being able to point to the Koran and Hadith to justify opposing the Hellenistic rational model and by 885 had persecuted and stamped out the rational movement and replaced it with the rejection of cause and effect, decreeing that things only happened because Allah wanted them to happen.

This is explained in the following quotation.

The use of rational arguments violated faith. Faith is not addressed to reason. Simply accept — bila kayfa (without saying how). As Ibn Hanbal declared, “Every discussion about a thing which the Prophet did not discuss in error.” Ibn Hanbal was said to have never eaten watermelon because there was no known instance of Muhammad having done so.

The name of the Ash’arite school came from its founder, Abu Hasan al-Ash’ari (873-935). Al-Ash’ari had been Mu’tazilite until the age of forty. He then announced: “He who knows me, knows who I am, and he who does not know me, let him know that I am abu al-Hasan ‘Ali al-Ash’ari, that I used to maintain that the Qur’an is created, that eyes of men shall not see God, and that the creatures create their action. Lo! I repent that I have been a Mu’tazilite. I renounce these options and I take the engagement to refute the Mu’tazilites and expose their infamy and turpitude.”

In voluntaristic Islamic thought, however, there are no natural causes to discount. As a result, reality becomes incomprehensible and the purpose of things in themselves indiscernible because they have no inner logic. If unlimited will is the exclusive constitutent of reality, there is nothing left to reason about. The primacy of will have no boundaries in reason. – The Closing of the Muslim Mind

Irrationality, Ash’aritism, and Sunni Muslims

Ash’aritism became the dominant logical framework within the Sunni religion, with the Mu’tazali “school” being the prevalent school of Shite Muslims, who are only dominant in one country, Iran.

Understanding The Ash’ari Versus Mu’tazilism Schism in Islam

This schism is explained in the following quotation.

Al-Mamun picked up the pro-science torch lit by the second caliph, al-Mansur, and ran with it. He responded to a crisis of legitimacy by attempting to undermine traditionalist religious scholars while actively sponsoring a doctrine called Mu’tazilism that was deeply influenced by Greek rationalism, particularly Aristotelianism. To this end, he imposed an inquisition, under which those who refused to profess their allegiance to Mu’tazilism were punished by flogging, imprisonment, or beheading. But the caliphs who followed al-Mamun upheld the doctrine with less fervor, and within a few decades, adherence to it became a punishable offense. The backlash against Mu’tazilism was tremendously successful: by 885, a half century after al-Mamun’s death, it even became a crime to copy books of philosophy. The beginning of the de-Hellenization of Arabic high culture was underway. – The New Atlantis

Ash’ari and the Denial of Cause and Effect

At the heart of Ash’ari metaphysics is the idea of occasionalism, a doctrine that denies natural causality. Put simply, it suggests natural necessity cannot exist because God’s will is completely free.

God wills every single atomic event and God’s will is not bound up with reason. This amounts to a denial of the coherence and comprehensibility of the natural world. – The New Atlantis


While al-Ghazali did defend logic, he did so only to the extent that it could be used to ask theological questions and wielded as a tool to undermine philosophy. Sunnis embraced al-Ghazali as the winner of the debate with the Hellenistic rationalists, and opposition to philosophy gradually ossified, even to the extent that independent inquiry became a tainted enterprise, sometimes to the point of criminality. some places, especially Central Asia, Arabic work in science continued for some time, and philosophy was still studied somewhat under Shi’ite rule. (In the Sunni world, philosophy turned into mysticism.) But the fact is, Arab contributions to science became increasingly sporadic as the anti-rationalism sank in.

The Ash’ari view has endured to this day. Its most extreme form can be seen in some sects of Islamists. For example, Mohammed Yusuf, the late leader of a group called the Nigerian Taliban, explained why “Western education is a sin” by explaining its view on rain: “We believe it is a creation of God rather than an evaporation caused by the sun that condenses and becomes rain.” The Ash’ari view is also evident when Islamic leaders attribute natural disasters to God’s vengeance, as they did when they said that the 2010 eruption of Iceland’s Eyjafjallajökull volcano was the result of God’s anger at immodestly dressed women in Europe. – The New Atlantis

Islam Versus Christianity

Far from accepting anything close to the occasionalism and legal positivism of the Sunnis, European scholars argued explicitly that when the Bible contradicts the natural world, the holy book should not be taken literally. Influential philosophers like Augustine held that knowledge and reason precede Christianity..Galileo’s house arrest notwithstanding, his (Augusine’s) famous remark that “the intention of the Holy Ghost is to teach us how one goes to heaven, not how heaven goes” underscores the durability of the scientific spirit among pious Western societies. Indeed, as David C. Lindberg argues in an essay collected in Galileo Goes to Jail and Other Myths about Science and Religion (2009), “No institution or cultural force of the patristic period offered more encouragement for the investigation of nature than did the Christian church.” And, as Baylor University sociologist Rodney Stark notes in his book For the Glory of God (2003), many of the greatest scientists of the scientific revolution were also Christian priests or ministers. – The New Atlantis

Estimating the Actual Impact of Rationalism on Muslim Society

While the discovery of Greek rational through to the final and complete rejection of this knowledge spans over 234 years, the effect of Greek rational thought was far shorter than this, as it was not immediately accepted, and the Mu’tazilis only “reigned” for a relatively short period of time.

Major Islamic Historical Dates

YearDiscovery or Caliphate Event
610Mohammed is proclaimed as prophet
623For first 13 years, Mohammed only accumulates roughly 100 followers.
628Defeats Jewish fortress of Kaybar
629Mohammed and his army conquers Mecca
632Beginning of Rashidun Caliphate
638Muslims Conquer Roman/Byzantine Syria
661End of Rashidun Caliphate
651Sassanid Persian empire is conquered in its entirety after 18 years of war.
661Beginning of Umayyad Caliphate
698Muslims conquer North Africa
750End of Umayyad Caliphate, which followed extreme Arab supremacy overall all other Muslims.
750Beginning of Abbasid Caliphate led to more power being shared with non-Arabs, and less expansionary foreign policy.
820Persian Muhammad ibn Musa al-Khwarizmi makes major contribution to what is now algebra, astronomy, trigonometry, geography.
825Al-Mamun pushes Greek rationalism, called Mu'tazilism, undermining Islamic scholars.
861Abassid empire splinters into many factions after 861 (Right around the rational schism)
880Excluding expansion into SE Asia 100s of years later, Islam does not expand much geographically from this point.
885Mu'tazilism is soundly defeated by irrational non cause and effect Ash'arism
950Islamic Discoveries Slow After This Point
1099Islamic law stops making progress.
1199Islamic Discoveries Completely Stop
1238Christian Europeans Take Back Cordoba
1250Christian Europeans Take Back Seville
1258End of Abbasid Caliphate
1258Beginning of Ottoman Caliphate
1492Christian Europeans take back Granada and push Muslims and Jews out of Iberia.
1512End of Ottoman Caliphate

The Reduction of Golden Age Discovery in 950

The Islamic Golden Age of Discovery is often presented as 500 years in duration. This in a way matches the cultural posturing of the Chinese, who often say theirs is the only civilization that goes back continually for 5,000 years. Or as the Chinese say “5,000 years of culture.”

However, clearly 500 years were not “golden.”

How Ash’aritism Would Have Shut Down Thought

The discoveries were less important to the later advancements in Europe that are often presented by Muslims, but the progress slowed considerably by 950. Because doing research that would propose cause and effect would normally get one persecuted by the dominant Ash’arites, it is not difficult to see why discoveries lagged after 950.


Discoveries and innovations from the Muslim world not only slowed to a trickle after 950 but tremendously lagged the output of western societies all the way to the present day. However, this is not that unusual. There is no society that is close to European-based societies (so including countries based on European culture like the US, Canada, Australia/NZ, etc..) that are not in Europe but are birthed from that culture. Muslims tend to focus on “what happened after the Golden Age,” without considering that the Golden Age of Islamic Discovery is in great part a project by Muslims designed to build Muslim self-esteem and that fits in the Islamic supremacy mental model that is built into Islam that declares all non-believers as inferior to Muslim believers. Muslim invaders took and took credit for the inventions and intellectual property of societies they conquered though while not militarily their equal, were significantly more advanced than them culturally.

This book is published by National Geographic. However, it is authored by a Muslim pride organization based in the UK that has little concern for historical accuracy. 

Muslims tried as hard as they could to continue to assert their superiority over these cultures, and now try to present the discoveries of these cultures as uniquely Muslim. When Muslims look to western societies, they again find themselves culturally inferior, and so they must flip the narrative such that there are superior, and The Golden Age of Islamic Discovery is a major part of this initiative, attempting to trace every European invention to a Muslim point of origin. Anyone who investigates and questions The Golden Age of Islamic Discovery is characterized as an Islamaphobe.