To properly study foreign cultures, an ethnographer must immerse himself into the foreigner's society, often stripping himself of all common necessities. This practice is most purely illustrated by the accounts of Jean de Lery and Mary Jemison. Jean de Lery, a French Calvinist, in his History of a Voyage to the Land of Brazil, examines the Tupinamba, an Indian tribe, by allowing himself to separate from his Protestant rationality. To ensure her own survival, Mary Jemison, an Irish American taken captive by Shawnee Indians and adopted by a Seneca family, fully assimilates herself into tribal life, living as a Seneca woman for seventy years. Though Lery's account is one of an ethnographer and Jemison's of a captive, both narrations have a perspective of their particular Indians that differs from the normal white stereotypes of their times. Specifically, Jemison and Lery accept Indian brutality as a moral right, allowing them to recognize the inherent peaceable nature of Indians. Their narrations, however, are more than ethnographic: Lery and Jemison deliberately examine acceptable Indian violence in relation to civilization, either as an affect of white society or in comparison to white society. In fact, beyond their praise of the Indians, Lery's and Jemison's narrations are in actuality critical examinations of white society.
Though Lery finds cannibalism to be the most treacherous crime a man can commit, he concludes that the Tupinamba's custom is a testament of their investment in vengeance. To Lery, the Tupinamba's use of cannibalism is justified by the seemingly automatic retaliatory mind-setting of the warring Indian tribes. Thus, the Tupinamba are not thirsty for blood but gain so much from seeking vengeance. Furthermore, Lery finds that the Tupinamba practice cannibalism only "toward their enemies" (Lery, p. 128). The ability to distinguish friend from foe illustrates to Lery the inherent morality of the Tupinamba.