Ptolemy (AD 87–150)

Of all Roman intellectuals, Claudius Ptolemaeus, or Ptolemy, perhaps more than any other classical scholar, did the most to influence subsequent European notions of geography for the next millennium by dominating the popular and literary view of Earth throughout the Middle Ages. Little is known of his private life. Greek by birth, as were many scholars during the Roman Empire, he spent his career in Roman Egypt at the famous museum at Alexandria, then the epicenter of intellectual life. Ptolemy was, among other things, a mathematician, an astrologer, and an astronomer who studied optics and refraction; the Arabs later credited him with the invention of the astrolabe. His greatest work in this domain was the geocentric Almagest, or “Great Treatise” concerning the movement of the sun, moon, and planets, the only surviving ancient text on astronomy.

But his greatest fame was in geography, which he took to mean the description of Earth as a whole. He differentiated between geography as the study of universals, topography as the study of localities, and chorography as the means of integrating the two scales. Ptolemy ridiculed Strabo's emphasis on individual regions, arguing instead for a holistic view encompassing the entire globe; he maintained that the regional emphasis was akin to painting a person by only showing his or her eye or ear.

In his famous eight-volume Geographia, a compilation of data about the geography of the Roman world, Ptolemy synthesized and extended Hipparchus's grid system of latitude and longitude for plotting the surface of the Earth, dividing it into 360 degrees and dividing each degree into seconds. It consists of the first known projection of a sphere onto a plane. The Geographia thus deployed a view of space as abstract, geometric, and homogeneous, invoking concepts derived from Euclidean geometry. He also attempted to map the known world with a map stretching from the Atlantic to China and speculated about the terra incognita (unknown territory). The Geographia became a canonical text in medieval Europe.

Although no Ptolemaic map survives, his descriptions formed the foundation on which the Western geographic imagination would be based well into the 16th century. His works were translated from Greek into Arabic in the 9th century and into Latin in 1406. During the Renaissance, Ptolemy, for all his errors, remained the chief classical authority to whom geographers turned in making sense of the newly unfolding world. When Columbus set forth on his voyage in 1492, it was Ptolemy's conception of the world that he relied on, although Ptolemy's estimate of the size of Earth was too small. Ultimately, however, colonial voyages of discovery and conquest put to rest Ptolemaic conceptions of Earth and opened the way for newer, more pragmatic accounts.

Figure 1 Ptolemaic world map from the 15th-century codex of Nicolaus Germanus

Source: National Digital Library of Poland.