This was the time when Baghdad was the most exciting place to be, if you were a person who was interested in new ideas, in pushing back the envelope of human understanding. Philosophy, mathematics, astronomy, geography, engineering – all were explored and developed here.
Mathematics was further developed as a tool to make sense of the world. Algebra was invented (the system of balancing the sides of an equation to find the value of an unknown, usually described as ‘x’). This, we non-mathematicians may not realise, is a powerful tool indeed. As are five of the six trigonometric functions, the names of which I remember from school. The sine was brought from India. The others (cosine, tangent, secant, cosine, cosecant, cotangent) were developed in Baghdad in this period. The Indian numbering system that we still use, of nine digits and a zero, was promoted and explored.
The practice of philosophy, of studying how to think about the human situation, was brought into the modern monotheistic world from that of the Greeks.
Engineering techniques (the valve, the crankshaft, feedback controls) were rescued from the ancient world, understood, refined and applied in new ways.
This drawing for a self-trimming lamp is one of a hundred entries in the Book of Ingenious Devices by the Banu Musa brothers. The book also contains instructions and the design for a water-powered musical instrument, a concept not attempted again for a thousand years.
The Banu Musa brothers, as well as the multi-talented al-Kindi (known as the father of arabic philosophy) and the extraordinary mathematician al-Khwarizmi, were all employed in the House of Wisdom, the Bayt al-Hikma.
Their employer was the caliph al-Mamun.
How did this all come together? A combination of factors. Here are some of them, in no particular order.
The first paper mill opened in Baghdad in 795. The technology of paper-making was as profound in its significance as the development of the printing press in renaissance Europe or the internet in our own lifetimes. While northern Europeans used scraped animal skins to write on, educated Baghdadis had libraries with hundreds or thousands of books.
Baghdad itself was located at the meeting point of the Persian and Indian cultures to the east and that of the Mediterranean (particularly Greece) to the west. There is a long history of cultural exchange between India and Persia. Baghdad had been built 50km north of the ancient Persian capital of Ctesiphon. Indian mathematicians and their ideas were welcome in Baghdad.
The religion of the rulers, islam, was tolerant of (most) other faiths. Christians, Jews and Zoroastrians had to pay a poll tax but were otherwise largely left to pursue their own beliefs. In fact the administration sometimes preferred them not to convert to islam. Mass conversion meant a drop in tax revenues. As Constantinople was pursuing a less tolerant line to unorthodox christianity at the time, many non-mainstream christians found it healthier to live in the muslim world. They brought ancient Greek texts with them, and could read them.
The schools of Athens and Alexandria, with a continuous tradition of learning going back to ancient Greece, had been closed a century or so earlier.
Islam values literacy. The Quran is to be read and recited, in arabic.
Arabic was the common language from Cordoba in the west to Kabul in the east. Some said that they found it easier to express the new ideas in arabic than their native language. It was the language of learning, as latin was in the medieval world and English is now.
The translation movement had been in progress for some time. As well as Indian mathematical texts, Greek medical, scientific and medical texts were brought to Baghdad and translated into arabic. Translators were well paid for their work, sometimes the weight of the finished book in gold. Not only the caliph, but many of the elite joined in the search for ancient texts to translate. It is said that a condition of a peace treaty between Baghdad and Constantinople was that a copy of Ptolemy’s Almagest should be made available to Baghdad. To understand these texts well enough to be able to translate them, advanced knowledge of the subject is required. This then facilitated a comparison of the different traditions. Where do Greek geometry and Indian mathematics coincide, for example?
The culture of Baghdad was one of exchange, of ideas as well as goods. The Prophet himself had been a trader. There was a stable administration. Recently, a written cheque has been found which was issued in Baghdad and cashed in Cordoba. Baghdad became rich.
There were tensions, too. The differences of view about the human’s relation to God came into sharp focus. This is the time when the hadith, the sayings of the Prophet, were collected and catalogued. The ulama, the imams, theological scholars, valued the Quran and the hadith above any discoveries by the philosophers and scientists. Some of the points of contention: Was the Quran created at a moment in time, or as it is directly revealed from God is it co-eternal with God? The caliph and the scholars of the House of Wisdom thought the former, the scholars of the ulama thought the latter. Does a person find the way to God via reason, working it out, or inspiration, faith, devotion?
Caliph al-Mamun was an advocate of reason over revelation. He loved the inquiry, the finding it out. (Among other projects, he despatched his scholars to measure the size of the Earth. Ptolemy had given an estimate in the Almagest, measured in stades, but nobody knew what a stade was.) Towards the end of his life al-Mamun issued a decree that the Quran was created. As he was caliph and therefore successor to the Prophet, he declared himself authorised to make such a pronouncement. Any imam who disagreed with him was to be punished. This was a dangerous precedent for the ulama, who saw themselves as the ones best qualified to interpret the wisdom of islam.
Inevitably this hardening of positions led to the creation of heroes and martyrs in those who resisted the caliph. Fifteen years after his death in 833 the decree was revoked and the pendulum began to swing in the opposite direction. The scholars of the House of Wisdom went elsewhere.