During the two first centuries of Portuguese colonization in America there was an intense debate about the legitimacy of enslaving Africans and Indians. In Portuguese America, the mission to spread the Christian faith was connected with the subjection of populations on both sides of the Atlantic Ocean to an ideology that considered labour as God's punishment for Adam's sin. In that sense, the justification of the unfree labour inflicted upon Indians and Africans in Portuguese America was a product of the same ideology, one that condemned manual work as rendering a man dishonourable. The purpose of this article is to review the debate from its medieval origins in Portugal, and to examine what effect the arrival of the Jesuits in America had on that debate, until the final prohibition of Indian enslavement in the mid-eighteenth century, documented by letters, reports, and sermons.