Flat or Globular? From the time of the fourth-century philosopher Anaximander, the ancients held to the belief that the earth was a globe. Until the work of Ptolemy in the second century C.E., most writers also believed that the inhabited world was a vast island surrounded by Ocean. The idea was not completely rejected until the time of Ptolemy, who speculated that there must be unknown lands beyond Asia. In the second century B.C.E. Crates of Mallos had already advanced the idea, though with incredible arguments, that the inhabited world of Europe, North Africa, and Asia was not the only inhabitable place on the globe. As Crates's theory had it, the globe could be divided into four regions, of which only one was known by actual exploration, the one that contained the continents of Europe, Asia, and Africa. Although...