9th century AD

The word for what Baghdad is doing in this century did not exist before it. Manuscripts are hunted in Byzantine libraries by state agents, bought, and given to salaried translators who work in teams and check one another. Hunayn ibn Ishaq describes his own procedure with a candour that would satisfy a modern editor: he lists which Greek manuscripts he could find for a given treatise of Galen, which were defective, where he had to reconstruct, and whether he translated into Syriac first and then Arabic or straight across. The point of saying so is that accuracy is contested and he expects to be checked.

Out of this comes something that is not translation. Al-Khwarizmi's book on restoring and balancing is not a commentary on anything Greek. It takes equations as things to be handled by a general procedure - move the unknowns to one side, complete the square, apply the rule - and it works through inheritance division and land measurement because those are the problems people bring. The Greeks had solved particular equations geometrically and brilliantly. This is a method any competent person can be taught, and that difference is the point.

The intellectual confidence has a sharp edge. The Mu'tazila argue that God's justice must be intelligible to reason, that the Qur'an is created rather than eternal, and for a period the caliphs enforce that position on unwilling scholars. Ibn Hanbal is flogged and imprisoned for refusing it. When the policy is reversed, the reversal is remembered as the triumph of scripture over speculation. The question at issue - whether reason may sit in judgement on revelation - is not settled by either outcome, and everyone involved knows the stakes are not academic.

Europe this century is being raided into a different shape. Viking crews arrive first for portable wealth and then for land, and the political effect is that authority devolves to whoever can actually mount a defence, which is the local lord with mounted men and a fortified place. Charlemagne's empire is divided among his grandsons at Verdun and the divisions harden into countries. In this same environment Eriugena, an Irishman at the West Frankish court, translates the Greek Dionysian corpus and writes a work of philosophical theology so ambitious that later centuries will find it alarming.

China reaches a turn that no one at the time reads correctly. In 845 the state suppresses Buddhist monasteries on a large scale, seizing land and metal and returning hundreds of thousands of monks to lay life. The stated reasons are fiscal and the deeper one is that a foreign religion holding that much wealth is a rival. Buddhism does not disappear, but the schools that survive best are the ones needing least institutional apparatus. Three years earlier, in Tibet, the empire that had taken Chang'an eighty years before comes apart entirely.

And almost invisibly, in the same decades, a Chinese printer finishes a scroll of the Diamond Sutra with a colophon giving the date and the donor's reason, and a Daoist writer warns that mixing saltpetre with sulphur and charcoal has burned down buildings and injured people. One is the earliest printed book that survives with a date on it. The other is the earliest description of gunpowder. Neither is presented as important.