Acceptance of the Arabic language helped promote learning. Beginning in the 8th century, Arabic became the language of scholarship and science throughout Islamic lands. A shared language and love of learning allowed scholars in Europe, North Africa, and the Middle East to exchange ideas and build on one another's work.
Muslim rulers built schools, colleges, libraries, and other centers of learning. From a small village, Baghdad grew into one of the world's largest cities. It became a major center of learning, where Persian influences combined with the Arabic heritage of Islam. There, Caliph al-Ma'mun founded the House of Wisdom in 830, where scholars from many lands gathered to do research and to translate texts from Greece, Persia, and India.
Like thinkers in Europe, thinkers in the Islamic world sometimes wondered how to make reason and logical proof agree with their faith. Al-Kindi, a 9th-century Arab philosopher, tried to resolve this issue. Humans, he said, had two sources of knowledge: reason and revelation by God. People could use reason to better understand the teachings of faith. Some truths, however, could be known only through God's word. For example, no one could prove that there would be a resurrection, or rising from the dead, on the day of judgment.
Ibn Sina (i-ben SEE-na), a Persian, is among the most famous of Muslim philosophers. Known as Avicenna in Europe, he wrote in the early 11th century. He believed that all knowledge could be known through revelation and reason. For example, he presented an argument that the soul was immortal. His writings were widely translated and influenced many thinkers in medieval Europe.