Despite President Obama’s recent suggestion, Columbus was anything but an unproblematic spokesman for innovative, modern, secular thought. Columbus was, instead, motivated by conservative prophetic and apocalyptic fears. He considered his voyage across the ocean as part of an effort to convert all the races of the world to Christianity before the end of the world. Columbus’s apocalyptic fears were fueled by his reading of Pierre d’Ailly’s Imago mundi. D’Ailly was bishop of Cambrai and worked to heal the Great Schism. Through d’Ailly’s text Columbus was influenced by Roger Bacon, the pseudo-Methodius, St. Augustine, among others. D’Ailly’s Imago mundi was particularly important for Columbus’s ideas about both the coming apocalypse and the size of the earth. He owned and annotated the 1483 edition of d’Ailly’s work.
Quite a number of Columbus’s annotations concentrated on chapter 8, “On the size of the habitable earth.” In this chapter d’Ailly surveyed the various opinions about how much of the earth was covered in water. Ptolemy, Aristotle, Pliny, and sacred texts disagreed, some claiming that as much as one quarter of the earth was covered in water and others claiming as little as one seventh. Columbus decided that scriptural references were correct and that only one seventh of the earth was covered in water.
The second important bit of information Columbus took from d’Ailly was the size of the earth. In chapter ten, “On the longitude and latitude of the climates,” d’Ailly reported the various ideas about the size of the earth. Citing the Arab astrologer Alfraganus, d’Ailly claimed that one degree at the equator equaled 56 2/3 miles “and thus the whole circumference is two thousand and four hundred miles” (from Pierre d’Ailly, Imago mundi (1483), fol. b1).
Columbus found support for his convictions in d’Ailly’s text. Further, Columbus was convinced that he had both experiential and textual evidence of the earth’s small size. In a letter to Ferdinand and Isabella he wrote:
The world is but small; out of seven divisions of it the dry part occupies six, and the seventh is entirely covered with water. Experience has shown it, and I have written it, with quotations from the Holy Scripture, in other letters, where I have treated of the location of the terrestrial paradise, as approved by the Holy Church; and I say that the world is not so large as vulgar opinion makes it, and that one degree from the equinoctial line measures fifty-six miles and two-thirds. That is a fact that one can touch with one’s own fingers.
(quoted in P.M. Watts, “Prophecy and Discovery: On the Spiritual Origins of Christopher Columbus’s ‘Enterprise to the Indies’,” American Historical Review 90 (1985): 73–102, quotation from 83)
So the question for Columbus wasn’t whether or not the world was round, but how big around was it. His work was convincing the Ferdinand and Isabella as well as their advisors that he was right, that it was only 2400 miles around.
The picture that emerges here is not one of a free-thinking, proto-modern Columbus struggling against the chains of an oppressive and conservative religion. Despite Andrew White’s fictions to the contrary, Columbus was not a warrior of rationality. He did not wage battle against the Church. And he did not “strengthen the theory of the earth’s sphericity” (A. White, A History of the Warfare of Science with Theology (1876), 19).
Columbus was, contrary to both White and Obama, deeply religious and motivated apocalyptic fears. His voyage westward seems to have been part of his efforts to bring Christianity to the peoples of the world, to save humans before Christ’s Second Coming and Judgement Day. He believed he could make that voyage because his sources had mislead him.