Influence of Other Writers on the Travels of Christopher Columbus
Understanding Earth's Geography
In an exploration of the mental world of early explorers such as Christopher Columbus through an analysis of the works upon which such explorers have based their travels and resulting discoveries, one may come to an assessment of how earlier works of geography and travel shaped the journeys and resulting discoveries of Christopher Columbus. Through a careful reading of Christopher Columbus’s written firsthand accounts including the prologue to his 1492 journal, a letter from Columbus to the king and queen of Spain, and other such primary sources, it is possible to assess the influence of such earlier thinkers as Ptolemy, Pliny, Abu Abdallah, Ibn Fadlallah, John Monte Corvino, Marco Polo, Sir John Mandeville, and others on Christopher Columbus’s explorations. Throughout his 1501 letter to the king of Spain, Christopher Columbus outlines his forty years of experience in the field of navigation, including his extensive interactions with scholars, religious clergy, educated travelers, as well as his consultation of the works of such experts as astronomers, geologists, geometrists, mathematicians, seamen, historians, and philosophers. Through an analysis of Columbus’ writings in conjunction with an analysis of the sources upon which Columbus based his research, historians may better understand the influences of previous writings on Columbus’ explorations.
In a letter from Columbus to the King and Queen of Spain in 1492, which serves as the prologue to his first voyage journal, Columbus explains that his religious motivations for conversion of India to Christianity are in appeal to an anti-Semitic King, whose Christian faith was so stringent that an expulsion of the Jews in January of 1492 through a royal edict seemed imminent and necessary. Through such a mission, Columbus explains throughout his letter that he expects to be deemed the viceroy, and perpetual governor of any islands, which he may discover and acquire for Spain in his travels. In his letter, Columbus also expresses his desire to map his route and comprise a book of maps and descriptions of the Atlantic Ocean for publication in Europe.
Upon an analysis of Columbus’ biography, The Life of Admiral Christopher Columbus written by his son Ferdinand following Columbus’ death, the use of the ideologies of Ptolemy, Marinus, and Alfragan throughout Columbus’ theories of navigation are explored. Written to improve Christopher Columbus reputation following his highly controversial gubernatorial reign over Hispaniola and suspect ruling tactics, Ferdinand explains in the biography that based on the works of Ptolemy and Marinus, Columbus believed the distance between Europe and India, by sea, was much shorter than it really was due to Ptolemy’s geographical analysis and Marinus’ astronomical studies of constellations applied to maritime travel. As asserted by Ferdinand, Columbus also based his understanding of earth’s size on the studies of Alfragan’s astronomy and the geography theories of the eight-century. Likewise, Ferdinand’s study of his father’s theories and book collection led him to conclude that his father’s use of Pliny’s theory of earth’s size heavily influenced his father’s exploration ideas. Ferdinand contends that his father’s reliance on the earth’s size theories and calculations of Marco Polo, John Mandeville, Pierre d’Ailly, and Julius Capitolinus, also held great influence over Columbus’ navigation theories. Ferdinand does not ignore the impact of the stories of travelers such as Martin Vincente and Pedro Carrea on his father’s philosophy of navigation, however he recognizes these potential sources served to validate the scholarly accounts on which Columbus based his research; and that such individual encounters were not the origin of Columbus’ navigational theories but instead confirmation of their correctness.
Ptolemy’s Geography, on which much of Columbus’ theories of earth’s size were based, uses measurements of shadows at various points on the earth’s surface, to calculate the circumference of the earth. Ptolemy bases his work on the studies of Marinus the Tyrian, upon whose work Ferdinand claims his father also relied heavily due to their presence within his personal library. Similarly, Pliny’s Natural History, upon which Columbus appears to have based his knowledge of geography, explains what Columbus might expect of the natives of islands such as those including the Cannibal Scythians, which he could potentially encounter. Such descriptions of Indian women and others such as the “umbrella foot” tribe exemplified Columbus’ perceived need to Christianize the East and lended validity to Columbus’ letters to King Ferdinand and Queen Isabella.
Abu Abdallah Mohammed Idrisi’s Geography, which Ferdinand asserts his father studied to aid in his navigational skill, provides a detailed description of the lands, which Columbus might encounter, and their distances from Columbus’ European homeland. Likewise, Ibn Fadl Allah Al’Umari’s Masalik Al Absar, supposed by Ferdinand to have been studied by Columbus, contends that upon a distant navigation from Europe, lands in which a population awaiting Christian conversion such as the mythical converts of the fictional accounts of Prester John reside.
 Weisner, Merry E., Julius Ruff, and William Bruce Wheeler. Discovering the Western Part: A Look at The Evidence, Vol. II Fifth Edition. (Boston: Houghton Mifflin Co. 2004), 271-273.
 Ibid., 278-280.
 Ibid., 280-283.
 Ibid., 283.
 Ibid., 284.
 Ibid., 286.
 Ibid., 289.
A Not-So-Unique Perspective
The Travels of Marco Polo, written by Manuel Komroff, is a testament to the knowledge of exploration upon which Columbus based his impending navigation to India via the Atlantic crossing. According to Komroff’s account of Marco Polo’s travels, many islands lay awaiting Christianity’s arrival, such as the inhabitants of places including the Isle of Males and the Isle of Females, five hundred miles south of Kesmacaran. The Travels of John Mandevill, a part of Columbus’ extensive collection of navigational and exploratory manuals and descriptions, compiled within his library is assumed by Ferdinand to have influenced his father’s understanding of the resources and potential riches, which may have awaited his exploration. Mandeville’s description of natural resources including lumber, spices, gold, silver, and other such resources, claims that “all things there is plenty, save only of wine.” Such claims of wealth could have encouraged Columbus by providing him with expectations of economic gains through his exploration and conversions through his future control of such islands, which he thought it likely he would discover, conquer, and acquire for Spain. Likewise, Pierre d’Ailly’s Imago Mundi describes islands rich with resources, there for the taking by persistent explorers. D’Ailly’s description of places in which “fruits are plentiful” and “great herds of elephants” roam, is contended by Ferdinand to have encouraged his father’s explorations.
In a letter to Columbus from Paolo dal Pozzo Toscanelli, Toscanelli explains his support of Columbus’ impending journey to India, and includes a letter formerly sent to Fernan Martins of Lisbon. In his letters, Tosanelli explains his perception of the map of the Earth with navigational precision, the possibility of Christian conversions, and acquisition of riches from Spain, similarly to Columbus’ later letters to Ferdinand and Isabella.  Throughout Columbus’ letter to Lord Raphael Sanchez, the treasurer of the King of Spain, Columbus explains his 1492 discoveries, including a detailed description of the potential for Christian conversions and acquisition of resources; to gain support and funding for further exploration. Unlike Columbus’ earlier letters to King Ferdinand and Queen Isabella, the letter to Sanchez is less speculative of what Columbus might find, and more to serve as encouragement of further exploration of what was now known to be in existence. Columbus’ explorations reflected his cultural assumptions based on previous writings of other explorers, geographers, geologists, cartographers, astronomers, and other scholars. Following his explorations, Columbus’ writings such as his letter to Lord Sanchez reflect Columbus’ yearning for further exploration, stylistically reminiscent of the writings of the aforementioned scholars and explorers; believed by Ferdinand to have largely impacted his father’s cultural and scientific understandings. Columbus’ perceptions of the cultures and lands he would encounter were shared through his letters such as those to Ferdinand and Isabella, and were later validated by his letter to Lord Sanchez. Columbus’ letter to Sanchez was not his new perception of the world held uniquely by Columbus, but was instead a continuation of a long tradition of trade, warfare, missionary establishment, and exploration of Europeans throughout the world around them.
 Ibid., 290-291.
 Ibid., 293-294.
A Shared Pool of Knowledge
According to historian Robert Paine, at the time of Christopher Columbus, the unknown was linked to the known through the notion of discovery “within a given canon of knowledge; note is taken of certain intellectual implications.” Paine contends that this cannon of knowledge included Ptolemy’s Geography, “together with other 'pre or non-Christian scientific authority” such as those asserted by Columbus’ son Ferdinand. Likewise, Karl Butzer contends that the works of Marco Polo and Pierre D’Ailly were heavily influential to Christopher Columbus’s explorations. According to historian Karl Butzer, “the discoverers, explorers, and observational scientists of the Renaissance were at best familiar with a very limited selection of classical works, that were frequently cited only for effect, sometimes in the final stages of revision. Columbus's consultation appears to have been very selective and from a derivative digest in his possession” such as those Ferdinand mentioned his father possessed in his personal library. According to historian E.G.R. Taylor, “whatever is not of Europe or of Africa is of Asia; so every fifteenth century schoolboy learned his lesson, and so Christopher Columbus must have learned it.”
While Taylor, Butzer, and Paine are speculative in their assessments of the sources of Christopher Columbus’ exploratory and navigational knowledge, it is clear through an analysis of the letters of Columbus and the biography compiled by his son that the sources outlined by Weisner were very possibly highly influential in Columbus’ exploration experience in the New World. Written to emphasize his competence and the potential for Spanish glory from what Columbus believed to be awaiting him across the ocean, the letters written by Columbus reflect an existing body of knowledge including Ptolemy, Marco Polo, and others spanning the centuries before the Columbus expeditions. Although there are no written documentations of the influences of former writings on Columbus’ expeditions written by Columbus himself, an analysis of the writings of Columbus in comparison to the sources upon which Ferdinand places his emphasis may help validate Ferdinand’s claims and lend credence to the arguments of historians such as Butzer, Paine, and Taylor.
 Paine, Robert. “Columbus and Anthropology and the Unknown” The Journal of the Royal Anthropological Institute, Vol.1, No.1 (Mar. 1995) pp.47-49.
 Butzer, Karl W. “From Columbus to Acosta: Science, Geography, and the New World” Annals of the Association of American Geographers, Vol. 82, No. 3, (Sep., 1992), pp. 543-565.
 Taylor, E. G. R. “Idee Fixe: The Mind of Christopher Columbus” The Hispanic American
Historical Review, Vol. 11, No. 3 (Aug., 1931), pp. 289-301
Butzer, Karl W.. “From Columbus to Acosta: Science, Geography, and the New World” Annals of the Association of American Geographers, Vol. 82, No. 3, (Sep., 1992), pp. 543-565.
Paine, Robert. “Columbus and Anthropology and the Unknown” The Journal of the Royal Anthropological Institute, Vol.1, No.1 (Mar. 1995) pp.47-49.
Taylor, E. G. R. “Idee Fixe: The Mind of Christopher Columbus” The Hispanic American Historical Review, Vol. 11, No. 3 (Aug., 1931), pp. 289-301
Weisner, Merry E., Julius Ruff, and William Bruce Wheeler. Discovering the Western Part: A Look at The Evidence, Vol. II Fifth Edition. (Boston: Houghton Mifflin Co. 2004)