favor of peacefully converting native peoples without enslaving them. Las Casas protested the treatment of natives by Spaniards, and in 1520 was granted an audience with the Holy Roman Emperor Charles V (Charles I of Spain). He asked instead for their peaceful conversion. In April 1550, Las Casas and Juan Ginés de Sepúlveda met in Spain for a debate on the rationalization of native American enslavement and its morality based on Aristotle's idea of natural slavery. Sepúlveda defended the position of the New World colonists, claiming that the Amerindians were "natural slaves." Las Casas countered that Aristotle's definition of the "barbarian" and the natural slave did not apply to the Indians, who were fully capable of reason and should be brought to Christianity without force or coercion. Sepúlveda reasoned that the enslavement of natives was a result of war: the "superior" was dominating the "inferior", and the Spaniards had every right to do so. See also Natural law Natural order (philosophy) Slavery Slavery and religion Slavery in ancient Greece Valladolid debate References Slavery Philosophy of Aristotle Natural law