Jim Al-Khalili in The Guardian:
Exactly 1,200 years after its foundation, I was born in Karradat Mariam, a Shia district of Baghdad with a large Christian community, a stone's throw away from today's Green Zone and a few miles south of the spot where one of Baghdad's most famous rulers was born in 786. His name was Abū Ja'far al-Ma'mūn. Half Arab, half Persian, this enigmatic caliph was destined to become the greatest patron of science in the cavalcade of Islamic rulers, and the person responsible for initiating the world's most impressive period of scholarship and learning since Ancient Greece. By the eighth century, with western Europe languishing in its dark ages, the Islamic empire covered an area larger in expanse than either the Roman empire at its height or all the lands conquered and ruled by Alexander the Great. So powerful and influential was this empire that, for a period stretching over 700 years, the international language of science was Arabic.
The teenage prince Ma'mūn would have known Baghdad at the height of its glory: a vast, beautiful city characterised by the domes and archways of its famously intricate Abbasid architecture. It had grown to become the world's largest city just 50 years after the first brick was laid, with some estimates putting its population at more than 1 million. Ma'mūn was not the only caliph to support scholarship and science, but he was certainly the most cultured, passionate and enthusiastic. As a young man, he memorised the Qur'an, studied the history of early Islam, recited poetry and mastered the newly maturing discipline of Arabic grammar. He also studied arithmetic and its applications in the calculation of taxes. Most importantly, he was a brilliant student of philosophy and theology, or more specifically what is referred to in Arabic as kalam, which is a form of dialectic debate and argument. The early Muslim theologians found that the techniques of kalam enabled them to hold their own in theological discussions with the Christian and Jewish scholars who lived alongside them, and who had had a head start of several centuries to hone their debating skills by studying the writings of philosophers such as Socrates, Plato and Aristotle – historical figures from ancient Greece whose names would certainly have been known to the young Ma'mūn. It is even quite likely that by the early 9th century, some of their work had already been translated into Arabic.
More here.