Rachel Newcomb is an anthropologist and the Diane and Michael Maher distinguished professor of teaching and learning at Rollins College. She is the author of “Everyday Life in Global Morocco.”

How does knowledge travel? It can be difficult in our Internet-driven era to envision how knowledge was shared in the ancient world. Historian Violet Moller’s “The Map of Knowledge: A Thousand-Year History of How Classical Ideas Were Lost and Found” re-creates the pathways by which scientific and philosophical texts were passed down from the classical world to the modern era.

Popular opinion seems to assume an unbroken connection from the ancient Greeks to the Renaissance, but after the decline of the western Roman Empire in 476 A.D., most of what is now Western Europe was in fragments. The rise of Christianity led to the destruction of libraries and nonreligious (hence “pagan”) texts, and “by the year 500, secular book production had effectively gone underground.” Moller enhances our understanding of the period from late antiquity until the Renaissance by highlighting the many cities where knowledge continued to thrive during the Medieval era, and where important manuscripts were lovingly translated and protected while elsewhere they had been reduced to ashes.

Moller argues that stable and prosperous empires, combined with tolerant and intellectually curious rulers, supported the flourishing of knowledge. She introduces this premise through a discussion of the ancient library of Alexandria, Egypt, built around 300 B.C. She follows the trail of works created by three scholars who at various times studied in ancient Alexandria: Euclid’s mathematical treatise “The Elements” (300 B.C.), Ptolemy’s astronomical compendium “The Almagest” (around 150 A.D.) and the 3 million-word body of medical knowledge produced by Galen (approximately 129-217 A.D.), which influenced what was known about medicine for the next 1,300 years. All three works, despite their inaccuracies, were tremendously influential in creating the foundation for contemporary math, astronomy and medicine. Yet no original copies remain — so how did these works spread and influence the world as we know it today?

Baghdad, the Mesopotamian “cradle of civilization,” is the first stop on the map of this journey. In the prosperous court of the Abbasid caliphate (750 to 1258), paper, a necessary tool of the scholar, arrived in 793 from China via the Silk Roads. Along with other innovations in bookbinding, it allowed for an impressive output of research, writing and translation. Euclid, Ptolemy and Galen were all translated from Greek into Arabic, and scholars used this knowledge to develop multiple scientific fields. One scholar, al-Razi, drew on Galen to establish psychology, pediatric disciplines, hospitals and the practice of clinical trials that used control groups. Influenced by Ptolemy’s calculations, other scientists were able to determine the Earth’s circumference to within 400 miles of today’s more accurate measurements. “At a time when many Europeans were living on turnips and trying to fend off the Vikings,” Moller writes, Baghdad’s scientists were fostering a “golden age of discovery and enlightenment,” even inventing the crankshaft, which didn’t make it to Europe until the 14th century and is still used in today’s engines.

Other cities also flourished during the Medieval period. In Spain, Cordoba and Toledo were important centers of knowledge. Cordoba was a major site of exchange for scientific ideas originating in the Middle East, and Moller describes the routes of translation as well as the new studies in science, philosophy and medicine that fed Cordoba’s impressive production of 70,000 to 80,000 books per year in its heyday. As Cordoba’s prominence began to wane, Toledo rose to importance. Located at the edge of Muslim and Christian lands and reconquered by Christians in 1085, Toledo attracted scholars from all over Europe. Moller imagines the journey that Gerard of Cremona might have taken from Italy to Toledo to survey its impressive collection of manuscripts. His translations, including “The Elements” and “The Almagest,” brought “the great ideas of ancient Greece and medieval Islam to Western Europe.” Translating more than 71 books from Arabic to Latin, Gerard of Cremona brought this ancient Greek knowledge back into Western Europe.

Finally, Moller describes how Salerno, Palermo and Venice became epicenters of medical and scientific knowledge in Italy from the 11th century onward. Particularly entertaining is how conquest became intertwined with learning in Palermo, as Norman conquerors with a sense of curiosity encouraged scientific inquiry. However, in Salerno, something peculiar was beginning to happen: Authors were taking credit for Arab scientific ideas without attributing them. It’s possible, Moller asserts, that this was done because of attitudes toward Muslims during the Crusades, but nonetheless, this erasure of sources led to the suppression of Muslim contributions to the history of science. “The Map of Knowledge” goes a long way toward restoring our understanding of their role.

Moller ends the journey with the introduction of the printing press to Europe by Johannes Gutenberg around 1450. As this invention spread, so too did the availability of books. Although new discoveries would bring into question the accuracy of Galen and Ptolemy (while Euclid’s “Elements” still remains relevant), the work of these scholars was essential to scientific development in the modern era. Such work, Moller argues, would not have been possible without the remarkable cities she highlights in “The Map of Knowledge,” renowned not just for their political stability and the scholars who were drawn to them, but also for “an atmosphere of tolerance and inclusivity towards different nationalities and religions.” Visiting them through Moller’s imagination, the reader is invited to marvel at how multicultural the ancient world was, and to consider how the foundational knowledge of the Western world did not simply leap from the ancient Greeks to modern times but was painstakingly preserved, analyzed and innovated upon for almost 1,000 years.

The Map of Knowledge

A Thousand-Year History of How Classical Ideas Were Lost and Found

By Violet Moller

Doubleday.
310 pp. $30