Defending the Spanish conquest of the Americas, Sepulveda argued that the Indians had forfeited their rights because they violated natural law by cannibalism and human sacrifice.

Las Casas defended the Indians not by denying the charges but by defending human sacrifice on the basis of natural law. “Be natural law,” he argued, “men are obliged to honor God, and to offer the best things in sacrifice,” since sacrifice is the best way to worship God. Since “nothing in nature is greater or more valuable than the life of man or man himself,” then “natural reason” shows that “men should be sacrificed to God.” Christians must condemn human sacrifice, and thus means that it is an error, but it is not an atrocity.

Besides, nearly every culture has offered human sacrifice, and Aristotle insisted “that must necessarily be judged to be good or better which is so judged by all, or the majority of persons of good judgment.”