The Introduction explains the purpose and scope of the book, and the research questions it addresses, as well as its place within recent scholarship – both in relation to works focusing on languages in Late Antiquity and to more theoretical studies of various forms of group identity and its attributes. We open with a discussion on changes in the linguistic views of the increasingly Christianized elites in the late antique Mediterranean and the ways they experienced and conceptualized linguistic differences. The chapter defines such important concepts as “metalinguistic comments,” “the alloglottic Other,” “communities of linguistic sensitivities,” “objectification of language,” “linguistic awareness,” and “a different language”; clarifies the linguistic and religious terminology to be used; outlines the geographical scope, chronological limits, and the range of primary sources analyzed; and describes the book structure. The Introduction also explicates possible methodological problems in research like this and suggests the ways in which one could overcome them –avenues this book further explores.