During the sixteenth century, true piety and virtue became issues of primary importance for the emergent Spanish imperial design which sought to define Catholic Orthodoxy and to evangelize the people of the newly discovered regions of America. The antagonists of the famous Contienda de Valladolid (1550), Bartolomé de Las Casas and Juan Ginés de Sepúlveda, were involved in responding to the emperor's inquiry about the legality of the war that Spaniards were waging against the indigenous people of the New World. The legal and political implications of their opposing arguments have been thoroughly studied by numerous scholars. Nevertheless, the main focus of this study is to explore the ways in which the implicit script of their work contributed to the religious debates of the century.

The ultimate question debated in Valladolid, I argue, was to inquire into and develop the methods and rules on how to preach and promote the Holy Catholic Faith in the New World, which was concerned, above all, with perfecting the life of the spirit. These evangelizing ideas appear in Sepulveda's Demócrates Segundo as well as the summarized content of Las Casas' De unico modo, whose doctrine served as the basis for his legal arguments during the dispute. Such emphasis reveals that, although Sepúlveda and Las Casas had differing interpretations of Aristotle's ideas and opposing views on the legitimacy of the conquest and colonization of America, the authors agreed on the need to readdress evangelization, given the new challenges posed by the cuarta terrae. This dissertation recovers the missionary plan outlined in the Valladolid Debate and examines the nuanced differences of the methods proposed by Las Casas and Sepúlveda. It suggests that Sepulveda proposes a quasi-natural way of Christianizing Amerindians that requires their submission to the Spanish government so that, by imitating a superior model, the naturally inferior beings would rise to the excellence prescribed by the law of nature and become Christians. On the other hand, Las Casas advocates a more natural way of arriving to the truth through a cognitive model that relies on their reasoning rather than on emotions, as was recommended by the ecclesiastical rhetoric of Fray Luis de Granada.