The world of Islamic civilization cohered not only as a network of faith but also as an immense arena of exchange in which goods, technologies, food products, and ideas circulated widely. Now large areas of the Afro-Eurasian world operated within a single political system, practiced Islam, and spoke Arabic. This huge region rapidly became a vast trading zone of hemispheric dimensions. In part, this was due to its central location in the Afro-Eurasian world and the breaking down of earlier political barriers between the Byzantine and Persian empires. Furthermore, commerce was valued positively within Islamic teaching, and laws regulating it figured prominently in the sharia, creating a predictable framework for exchange across many cultures. The pilgrimage to Mecca, as well as the urbanization that accompanied the growth of Islamic civilization, likewise fostered commerce. Baghdad, established in 756 as the capital of the Abbasid Empire, soon grew into a magnificent city of half a million people. The appetite of urban elites for luxury goods stimulated both craft production and the desire for foreign products.

Thus Muslim merchants, Arabs and Persians in particular, quickly became prominent and sometimes dominant players in all the major Afro-Eurasian trade routes of the third-wave era—in the Mediterranean Sea, along the revived Silk Roads, across the Sahara, and throughout the Indian Ocean basin (see Chapter 7). By the eighth century, Arab and Persian traders had established a commercial colony in Canton in southern China, thus linking the Islamic heartland with Asia’s other giant and flourishing economy. Various forms of banking, partnerships, business contracts, and instruments for granting credit facilitated these long-distance economic relationships and generated a prosperous, sophisticated, and highly commercialized economy that spanned the Old World.

The vast expanse of Islamic civilization also contributed to ecological change as agricultural products and practices spread from one region to another, a process already under way in the earlier Roman and Persian empires. Among the food crops that circulated within and beyond the Islamic world were different varieties of sugarcane, rice, apricots, artichokes, eggplants, lemons, oranges, almonds, figs, and bananas. Equally significant were water-management practices, so important to the arid or semi-arid environments of many parts of the Islamic world. Persian-style reservoirs and irrigation technologies spread as far as Tunisia and Morocco, the northern fringes of the Sahara, Spain, and Yemen. By connecting different environmental zones, particularly those where water availability was the major obstacle to agricultural growth, particular regions could draw upon a wide range of crops and practices. All of this contributed to an “Islamic Green Revolution” of increased food production as well as to population growth, urbanization, and industrial development across the Islamic world.

Technology too diffused widely within the realm of Islam. Muslim technicians made improvements on rockets, first developed in China, by developing one that carried a small warhead and another used to attack ships. Papermaking techniques entered the Abbasid Empire from China in the eighth century or earlier, with paper mills soon operating in Persia, Iraq, and Egypt. This revolutionary technology, which everywhere served to strengthen bureaucratic governments, passed from the Middle East into India and Europe over the following centuries. Everywhere it spurred the emergence of books and written culture at the expense of earlier orally based cultural expressions.

Ideas likewise circulated across the Islamic world. The religion itself drew heavily and quite openly on Jewish and Christian precedents. Persia also contributed much in the way of bureaucratic practice, court ritual, and poetry, with Persian becoming a major literary language in elite circles. Scientific, medical, and philosophical texts, especially from ancient Greece, the Hellenistic world, and India, were systematically translated into Arabic, providing an enormous boost to Islamic scholarship and science for several centuries. In 830, the Abbasid caliph al-Mamun, himself a poet and scholar with a passion for foreign learning, established the House of Wisdom in Baghdad as an academic center for this research and translation. Stimulated by Greek texts, a school of Islamic thinkers known as Mutazalites (“those who stand apart”) argued that reason, rather than revelation, was the “surest way to truth.”30 In the long run, however, the philosophers’ emphasis on logic, rationality, and the laws of nature was subject to increasing criticism by those who held that only the Quran, the sayings of the Prophet, or mystical experience represented a genuine path to God.

But the realm of Islam was much more than a museum of ancient achievements from the civilizations that it encompassed. Those traditions mixed and blended to generate a distinctive Islamic civilization with many new contributions to the world of learning. (See Snapshot, above.) Using Indian numerical notation, for example, Arab scholars developed algebra as a novel mathematical discipline. They also undertook much original work in astronomy and optics. They built on earlier Greek and Indian practice to create a remarkable tradition in medicine and pharmacology. Arab physicians such as al-Razi and Ibn Sina accurately diagnosed many diseases, such as hay fever, measles, smallpox, diphtheria, rabies, and diabetes. In addition, treatments such as using a mercury ointment for scabies, cataract and hernia operations, and filling teeth with gold emerged from Arab doctors. The first hospitals, traveling clinics, and examinations for physicians and pharmacologists were also developed within the Islamic world. In the eleventh and twelfth centuries, this enormous body of Arab medical scholarship entered Europe via Spain, and it remained at the core of European medical practice for many centuries.