José de acosta (1539–1600) was a Jesuit who served as a missionary in Peru from 1571 to 1587. His Historia natural y moral de las Indias (1590) was an extremely influential description of the history, geography, and ethnography of the New World and was translated into English by Edward Grimstone in 1604. Like Las Casas, he opposed the oppression and over-taxation of the Native Americans and had several audiences with King Philip II, who favored his views over those of Sepúlveda.

That the incapacity of the Indians proceeds not from nature but from upbringing and custom

I shall add something that I think of the highest importance. In every respect, the Indians' slowness of mind and savagery are not caused by factors of birth, origin, or native climate but by their daily upbringing, and by habits not greatly dissimilar from the life of beasts. I have indeed been convinced of this for a long time, and am now unshakeably assured by hard facts. If one considers the matter soundly, upbringing generally plays a far larger part in human intelligence than birth. Ancestry and country admittedly have considerable force: corroborating the poet Epimenides, the Apostle Paul wrote, “The Cretians are alway liars, evil beasts, slow bellies” (Titus 1:12), as though nationality contributed much to perversity of customs. The observation of another poet, however, is also widely known: “You would think him a Boeotian, born where the air is dense” (Horace, Epistles 2.1.244).