Geography. Having been influenced by traders' successes, especially the exploits of Far Eastern merchants, explorers became the foremost proponents by the end of the Middle Ages of a connection with other lands. Their background as warriors or merchants and their love for adventurous travel formed their belief that exploring would be useful for their lives and their society. To that end they envisioned a new kind of formal outing that would reveal the world's future boundaries. Until 1492, however, what Ptolemy had displayed in his Geography (second century C.E.)—a world limited to the Mediterranean basin and its adjacent hinterlands, northern Africa, and parts of Asia— would not be extended. Drawn in about 1300, England's Hereford Mappa Mundi included nothing farther away than Eden, at the eastern extreme from Britain.

Roman Legacy. The medieval Christians' ideas departed little from the fundamental geography...