In 1550 and 1551, Juan Ginés de Sepúlveda and Bartolomé de Las Casas engaged in a significant debate over the justification of the Spanish conquest of the New World before the Royal and Supreme Council of the Indies at Valladolid. Their arguments reflected a longstanding tradition of just war theory, shaped by two generations of Spanish philosophers, theologians, and legal experts. Sepúlveda, in his unpublished dialogue, presented four key arguments advocating for the legitimacy of the conquest. These arguments were articulated through a learned Greek character, Democrates, who defended the Spanish position against a pacifist German named Leopold, echoing views similar to those of Erasmus of Rotterdam. The arguments included the barbarian status of indigenous people, their offenses against Natural Law, the need for humanitarian intervention due to practices like human sacrifice, and the right to free religious and cultural exchange. Sepúlveda cited esteemed philosophers such as Augustine, Thomas Aquinas, Ulpianus, and Aristotle, whose theories influenced his reasoning. This application of Aristotle’s concept of natural slavery to the indigenous populations drew severe criticism from Las Casas and other contemporary theorists, ultimately preventing the publication of Sepúlveda’s dialogue until a few manuscripts were rediscovered in the late 19th century.
