Points and lines were the stellar guides not only of the Babylonians but eventually also of Pytheas from Massalia (presently Marseilles), the Greek traveler who some time before 320 BCE left his home town for an adventurous journey to the northernmost limits of the oikumene. Most people still thought of the land mass of Europe, Asia, and Libya (that is, Africa) as a huge island surrounded by a big Ocean. It was Anaximander who initiated the radical thought which eventually made the mythical image of the Ocean fade into the rational geography of later explorers, most prominent among them Alexander in the southeast and Pytheas in the northwest. It has been suggested that the real reason Pytheas undertook his voyage was that he wanted to verify what geometry had already taught him. This chapter also examines Eratosthenes' work in geography, geodesy, and cartography, focusing on latitude and longitude, which came to form the skeleton of his world map, as well as Ptolemy's use of the terms “lines” and “labels” for what modern semioticians call visual marks and proper names.
Keywords: Pytheas, oikumene, Ocean, geography, Eratosthenes, cartography, world map, Ptolemy, latitude, longitude