European expansion had multiple causes. By the middle of the fifteenth century, Europe was experiencing a revival of population and economic activity after the lows of the Black Death. This revival created demand for luxuries, especially spices, from the East. The fall of Constantinople and subsequent Ottoman control of trade routes created obstacles to fulfilling these demands. Europeans needed to find new sources of precious metal to trade with the Ottomans or find trade routes that bypassed the Ottomans.

Religious fervor was another important catalyst for expansion. The passion and energy ignited by the Christian reconquista (reconquest) of the Iberian Peninsula encouraged the Portuguese and Spanish to continue the Christian crusade. Overseas exploration was in some ways a transfer of the crusading spirit to new non-Christian territories. Because the remaining Muslim states, such as the mighty Ottoman Empire, were too strong to defeat, Iberians turned their attention elsewhere.

Combined with eagerness to earn profits and to spread Christianity was the desire for glory and the urge to chart new waters. Scholars have frequently described the European discoveries as a manifestation of Renaissance curiosity about the physical universe. The detailed journals many voyagers kept attest to their wonder and fascination with the new peoples and places they visited. Eagerness for exploration was heightened by a lack of opportunity at home. After the reconquista, young men of the Spanish upper classes found their economic and political opportunities greatly limited. The ambitious turned to the sea to seek their fortunes.

Their voyages were made possible by the growth of government power. The Spanish monarchy was stronger than before and in a position to support foreign ventures. In Portugal, explorers also looked to the monarchy, to Prince Henry the Navigator in particular, for financial support and encouragement. Like voyagers, monarchs shared a mix of motivations, from the desire to please God to the desire to win glory and profit from trade. Competition among European monarchs and between Protestant and Catholic states was an important factor in encouraging the steady stream of expeditions that began in the late fifteenth century.

The people who stayed at home had a powerful impact on the process. Royal ministers and factions at court influenced monarchs to provide or deny support for exploration. The small number of people who could read served as a rapt audience for tales of fantastic places and unknown peoples. Cosmography, natural history, and geography aroused enormous interest among educated people in the fifteenth and sixteenth centuries. One of the most popular books of the time was the fourteenth-century text The Travels of Sir John Mandeville, which purported to be a firsthand account of the author’s travels in the Holy Land, Egypt, Ethiopia, the Middle East, and India and his service to the Mamluk sultan of Egypt and the Mongol Great Khan of China. Although we now know the stories were fictional, these fantastic tales of cannibals, one-eyed giants, men with the heads of dogs, and other marvels convinced audiences through their vividly and persuasively described details. Christopher Columbus took a copy of Mandeville and the equally popular and more reliable The Travels of Marco Polo on his voyage in 1492.