Al-Ghazali's Break

Abu Hamid al-Ghazali, who died in 1111, wrote the Incoherence of the Philosophers, a sustained attack on the Aristotelian philosophers of the Islamic world, principally al-Farabi and Ibn Sina. It is a serious work of philosophy, and its most famous argument concerns causation: that what we call cause and effect is observed conjunction rather than demonstrated necessity, and that the connection is sustained by God rather than by the natures of things.

A widespread account holds that this book ended scientific enquiry in the Islamic world by undermining the rational basis for investigating nature. The account is popular, it appears in general histories, and it does not survive the dates.

Ibn Rushd wrote the Incoherence of the Incoherence in reply later in the same century. The Maragha observatory, which produced the mathematical models that would appear in Copernicus, operated in the thirteenth. Ibn al-Shatir, whose lunar model is mathematically identical to one Copernicus used, worked in Damascus in the fourteenth. Ulugh Beg's observatory at Samarkand produced its star catalogue in the fifteenth. Ottoman, Persian and Indian scientific work continued well beyond that.

Four centuries of productive astronomy after the book that supposedly ended it. Whatever caused the eventual relative decline, the cause was not published in 1095.

The causal argument is also worth taking seriously on its merits rather than as a villain's motive, because it is close to the one David Hume would make six hundred years later. The claim that necessary connection is not given in observation is a genuine problem in the philosophy of science and remains unresolved. Al-Ghazali reached it first and it is not obvious that he was wrong.

What the popular account is doing is looking for a single sufficient cause for a diffuse historical change, and preferring an intellectual one because intellectual causes are legible and satisfying. The historians who work on the actual decline point at other things: the reorganisation of trade routes after the Atlantic passages opened, political fragmentation and invasion, the funding structure of scholarship shifting toward religious endowments with narrower remits, and the printing press arriving late.

That last one deserves more attention than the philosophy. Printing in Arabic script was resisted and delayed for reasons involving calligraphic tradition, the guild interests of copyists, and religious concern over the reproduction of sacred text. Europe had presses from the 1450s. Sustained Arabic printing in the Ottoman lands is an eighteenth-century phenomenon. Three centuries of divergence in how fast a text can propagate is a more plausible engine of divergence than a book of philosophy.

The archive's interest in this is methodological rather than regional. The single-cause explanation for a civilisational change is nearly always wrong, and it is nearly always attractive because it assigns responsibility.

It also has a use, which is why it persists. A story in which Islamic science ended because a theologian argued against philosophy is a story with a moral about religion and enquiry, and people who want that moral will keep the story regardless of the dates.

The dates are checkable. Maragha is thirteenth century. Samarkand is fifteenth. The book is 1095.