It is surely harmful to souls to make it a heresy to believe what is proved.
― Galileo Galilei
There is a presumption nowadays that "progress" is an inevitable improvement, that the slow meandering of culture will by some invisible hand of morality tend towards an ever greater good. "The arc of the moral universe is long", Theodore Parker once said, "but it bends toward justice". Those words pronounce a sense of safety, assuring us that our hard-fought battles, once won, stay won forever.
But that is not true.
A Tree Begins With a Seed¶
For him who seeks the truth there is nothing of higher value than truth itself; it never cheapens or debases him who reaches for it but ennobles and honors him.
In the annals of history since the unification of the Arab world under Muslim conquest, one period clearly stands as the pinnacle of its tolerance and learning, of its innovation and openness. It is not, as the presupposition of progress might have you believe, towards the end of that history, but rather towards the beginning.
In the 8th century, there arose in the Muslim world the Mu'tazili school of Islamic theology, often called a "rationalist" school of Islam. It was at one time the favored position of the Umayyad Caliphate, the second Muslim caliphate which came into dominance thirty years after the death of Mohammed. While the Umayyads asserted this position in a particularly intolerant way, there can be little doubt that philosophical inquiry was at the heart of their highest values.
Immediately following the Umayyad Caliphate, the Abassid Caliphate came into power, and quickly became one of the strongest patrons of philosophy the world has seen. The Abassids heavily sponsored the Translation Movement which brought Greek philosophy into the Arabic world. Several of the world's greatest philosophers grew directly out of this movement, including Al-Kindi, Al-Farabi, and of course Avicenna.
Forgetting is the Plague of Knowledge¶
The heretics in our times have heard the awe-inspiring names of people like Socrates, Hippocrates, Plato, Aristotle, etc. They have been deceived by the exaggerations made by the followers of these philosophers... that the mathematical, logical, physical and metaphysical sciences developed by them are the most profound... They refused to be content with the religion followed by their ancestors. They flattered themselves with the idea that it would do them honour not to accept even truth uncritically.
...It was only a few persons having irresponsible views and perverted minds who denied these principles. But in serious discussions no importance can be attached to such persons ; and no notice ought to be taken of them. And they must be branded with diabolical perversity and stupid contumacy, so that their example may be a deterrent to people who tend to think that a vainglorious conversion to unoriginal heresy would be an indication of intelligence and good sense.
...If someone says: Now that you have analysed the theories of the philosophers, will you conclude by saying that one who believes in them ought to be branded with infidelity and punished with death?
We shall answer: To brand the philosophers with infidelity is inevitable.
― Al-Ghazali, "The Incoherence of the Philosophers"
As the Seljuk Empire rose and contested for cultural dominance with the Abassids, the Seljuks founded "Nizamiyyah", institutions which combined philosophical teaching with religious policing to centralize ideological control and ensure their influence rose to dominance. Al-Ghazali, one of the teachers at the Bagdhad Nizamiyyah, quickly penned as part of that project a work, "The Incoherence of the Philosophers", reproduced in part above, which widely recognized as a pivotal turning point in Arabic thought.
As quoted above, Al-Ghazali explicitly condemned to death any who disagreed with his strict list of philosophical points. Of those points, the most contrary to rational inquiry was "Occasionalism": in direct contrast to much of the tradition before him,1 Al-Ghazali advocated the position that any talk of causation was heresy, because claiming that some cause would have some effect stripped God of his sovereignty, because it did not recognize that in fact effects only occur at God's whims.2 This attitude still persists in many places in the Arab world to this day.
Because of these positions, investment into the Nizamiyya did not spur learning in the Arab world, but extinguished it. Though ostensibly an institution of learning, it instead set its sight on correcting wrong-think, and the sciences, cancelled for their inherent heresies, quickly withered away.3 Astronomy was the only field which continued to innovate after this declaration, because it made predictions without making any causal claims and because those predictions were important for religious observance. Averroes, whose ideas became a foundation of philosophy in the West, was labelled a heretic in the course of his disagreements with Al-Ghazali, and many of his works were burned, and he was banished from his home of Córdoba. The policing of thought had put and end to reason.
If the growth of reason is to continue, and human rationality to survive, then the diversity of individuals and their opinions, aims, and purposes must never be interfered with.
― Karl Popper
Like all social technologies, reason is a verb ― a process, not a product. This feature, from which reason derives its timelessness, also portends the possibility of its demise. Unlike monuments or fixed institutions, reason exists as an action to be performed and is constantly reified in the minds of those who practice it. Entropy, the bane of the material world, cannot neither sully its clarity nor erode its utility. Yet that same foundation ― continuous reification ― requires a constant upkeep, without which its flame can burn out. Like with writing, which was lost to the Mayans and to the Mycenaeans, a disruption in practice in a single generation can lead to ruin beyond revival.
Each generation is responsible for maintaining the life of those principles which it holds dear. If you lead a life without reason's principles, then you have nothing to fear. But if stars fill your sky, if guiding lights of philosophy light your way, if you stand on the shoulders of giants and strive to see ever farther, then know that the tools you wield are not dead tools. Reason is alive, and it can die. It has died before, and it may die again.
The knowledge of anything, since all things have causes, is not acquired or complete unless it is known by its causes. Now it is established in the sciences that no knowledge is acquired save through the study of its causes and beginnings, if it has had causes and beginnings; nor completed except by knowledge of its accidents and accompanying essentials. Of these causes there are four kinds: material, efficient, formal, and final.
Mokyr, A Culture of Growth, 2017.↩