10th century AD

If you could see the whole world at once in this century, the thing that would strike you is how many centres there are and how little they know of each other's best work. Cordoba, Cairo, Baghdad, Constantinople, Kaifeng and Kyoto are all doing serious intellectual work simultaneously, and the traffic between them is thin and mostly one-directional.

In the Islamic world the confident phase of translation is over and what follows is argument. Al-Razi keeps case notes and, in a monograph on smallpox and measles, does something the Greek corpus never did: he distinguishes two diseases by watching how they present and progress rather than by fitting them into a humoral scheme. He is also willing to say that Galen was wrong where his own observations disagree, and to say it in print. Al-Farabi meanwhile builds a philosophical account in which prophecy and philosophy reach the same truths by different faculties, which is either a defence of revelation or a domestication of it depending on who is reading.

Jewish learning reaches a turn. The Babylonian Talmud has been closed for some generations, and the geonim of the Iraqi academies are answering questions from communities across the Mediterranean by letter, building a body of responsa. Saadia Gaon translates the Bible into Arabic for Jews who no longer read Hebrew easily, and writes a systematic defence of belief using the same rational tools the Muslim theologians use, because that is the argument he is actually in.

China after a half century of division is reunified by a dynasty that draws a deliberate lesson from the Tang collapse: generals brought down the last order, so this one will be run by examined civil officials and the army kept under civilian control. The consequences are enormous and mostly unintended - a state that prints money because it needs to move value faster than metal allows, a north Chinese iron industry burning coal at a scale Europe will not reach for eight hundred years, and a scholar-official class whose taste produces the landscape painting where mountains are enormous and the traveller at the foot of them is two brushstrokes.

In Japan the court at Heian has been left largely to itself for a century, the embassies to China discontinued, and a distinct literature grows in the gap. It is written substantially by women, in the vernacular syllabary rather than in Chinese, because Chinese is the men's official medium and the women are writing about what they actually notice. Within a few years of this century's end that will produce a long prose narrative about a courtier's emotional life that has no precedent anywhere.

Latin Europe is the poorest of these worlds and is beginning to notice. Gerbert of Aurillac studies in Catalonia, where Arabic learning is accessible, comes back with the abacus and the astrolabe, teaches at Reims and ends as pope, and is remembered by some as a magician because his mathematics is unfamiliar. Otto I stops the Magyar raids at the Lechfeld and has himself crowned emperor, reviving a title that had been vacant in the west. The monasteries have their libraries and the cathedral schools are starting.

Nobody in 990 would identify Europe as the coming power, and nobody would be wrong to omit it.