In general, the purpose of ethnographic writing is to define a group of people by shared cultural traits, such as language, religion, dress, hairstyle, marriage customs, and other social norms. Ethnography can be used either to integrate different peoples or to separate them. Usama ibn Munqidh's ethnography of the "Franks" (an excerpt from his autobiography) and William of Rubruck's ethnography of the Mongols (written during his voyage to Asia) fit the latter model. Both were written by visitors to foreign cultures, and both define structural oppositions between cultures in their narratives in order to divide their subject cultures from their own.

Usama creates such structural oppositions between his Arab society and the "Franks" (European Christians) so as to define the latter as alien. In his chapter on "Frankish Medicine", Usama tells of an Arab-trained doctor, Thabit, who goes to heal a woman who suffers from consumption. Thabit prescribes for her a "refreshing diet" which apparently aids her recovery. However, a Frankish doctor countermands Thabit's order, and instead cuts the woman's hair off. When she fails to heal, he removes her brain and rubs the inside of her skull with salt, killing her instantly.1 Usama relates this episode to establish the opposition as he sees it between the educated, scientific Arabs and the ignorant, superstitious Franks. Usama does the same when he describes the wine seller who catches another man in flagrante delicto with his wife, but merely threatens legal action against the interloper if he ever catches the couple together again. The Franks have no sense of jealousy and marital propriety, while the Arabs are implied to be protective of their wives. Usama also makes observations about the deceitfulness of the Franks: the Frankish King promises safe-conduct for Usama's family, but then decides to pillage their ship. Implicit here is the opposition between dishonest Franks and trustworthy Arabs. Overall, the Arab reader would get the impression that the Franks are hopelessly uncivilized and, since they are firmly entrenched in their ways, have no hope for change.

William of Rubruck, a French subject, sets up similar oppositions in his description of the Mongols in order to create a contrast between civilized Europeans and uncivilized Mongols. The Mongols live in movable tents and "have no abiding city."2 In contrast, Europeans live in fixed homes and are increasingly urban: if they do not live in a city, the regional seat of power is probably at least located in one. The opposition between nomadic Mongols and sedentary Europeans is thus produced. William goes on to describe the "shameful custom" of Mongol sons taking their late fathers' wives (except their own mothers) as their own.3 In a Christian culture, this practice would be immoral and illegitimate. Therefore, William creates an opposition between the proper marriage customs of Europeans and the improper ones of the Mongols. Mongols also give birth standing up instead of lying down, drink cosmos instead of beer and wine, and barter instead of trading in a market economy. All of these oppositions define the Mongol ethnic group as foreign to Europeans.

Usama's narrative undoubtedly establishes the Franks as an inferior group to the Muslims. Of course, he does not explicitly state his reasons for doing so, but possible motives can be deduced from the historical circumstances. Usama was writing during the first century of the Crusades. Christians, called to war by Pope Urban II, had invaded the Holy Land. In order to retake the conquered land, the Muslims had to organize and motivate their forces. Usama could be attempting to disgust his fellow Arabs with the Europeans occupying the Holy Land. After reading his descriptions, Muslims would become angry that such a barbarous people held on to what was rightly Muslim territory, thus encouraging them to join the battle against the Christians. Usama could also have had personal motivations. He was a foreigner in the Christian culture, and he must have felt very alienated. Usama could have written this text to bolster his self-confidence by giving himself a feeling of superiority. This would have aided him in retaining his own cultural values even though he was in the minority. Of course, the possible political and personal goals are not mutually exclusive, but compatible.

William's account makes the Mongols seem uncivilized, but not necessarily uncivilizable like the Franks. William's background as a Franciscan friar influenced his perspective considerably: the Franciscans placed heavy emphasis on preaching the Gospels and missionary activity.4 Therefore, it is not surprising that William's account leaves hope for conversion of the Mongols to Christianity. He has Mangu Chan remark about the Mongol soothsayers that "we do what they tell us, and live in peace."5 Indeed, the soothsayers are believed to influence the weather, foretell fate, and have other powers very useful to a steppe nomad culture. That is, the Mongols possess a pragmatic religion, not a revealed one like Christianity. William seems to believe that if he had only had the chance, he could have brought the Chan to Christ, but he "had neither the opportunity nor the time to put the Catholic Faith before him".6 In his ardor to convert the Mongols, William requests the opportunity to return to the Chan's court, presumably with other missionaries. Regrettably for the Church, he is never able to. Perhaps part of his motive in constructing the ripe-for-conversion Mongol "other" is to motivate the King and others who would read his account to send other missions to convert the Mongols. While certainly bringing salvation to the Mongols was attractive to William, he likely had other reasons as well.

William's chronicle reflects the process of colonization that the contemporary European core (here, France) imposed on the peripheries of Europe in the High Middle Ages. In the religious sphere, missionaries brought the orthodox Christian religion to people outside its base of influence. The Mongols could not easily be conquered militarily by Western Europe, but Europe's religion had a chance of replacing their varied systems of belief. In doing so, Europe would gain cultural hegemony over the Mongols, and thus likely reduce their aggression. The King of France, to whom William was writing, would certainly be receptive to this idea.

Usama's account has no similar hope of converting the Christians to Islam, perhaps because the Arab world was not so aggressive as Europe in exporting its culture. While William looks to expand the Christian world, Usama simply justifies the recapture of lost Muslim lands. The different functions of their two ethnographies illustrate the great adaptability of ethnography: a writer can twist it in whatever manner his goal demands.