Polemical texts are rather problematic documents for the study of cultural and ideological exchange. On the one hand, they often constitute our only sources on the opposition and debates between two opposing groups such as political parties, confessional communities or theoretical schools. On the other hand, it is now widely known that the rhetorics of controversy could be used as a mere literary device serving other purposes. For instance, some dialogues feature a Christian hero interacting with a fantasised, ideal-typical Jew in order to expose the fundamental elements of the trinitarian doctrine; a predicator could also expose the second figure to the scorn of Christian attendants, so that they feel more confident in the superiority of their own faith. However, it cannot be ruled out that some polemical texts were written as part of actual debates, either as direct contributions or as means to teach the readers how to respond to some arguments. In Late Antique, Byzantine and Islamic studies, scholars cannot usually benefit from many external sources, so they must investigate this matter from the texts themselves. In this communication, I will suggest methodological ways to conduct such investigation, indicating how and under which conditions some various criteria may be applied, including internal features of the text (genre, literary and rhetorical devices, intended audience and objectives) and intertextuality (comparing with texts written by the alleged opponents, as well as with works by the same author or other writers belonging to the same milieu or tradition). I will illustrate my points using examples taken from my doctoral research, which focuses on Greek polemical texts written by Christians in Syria, Palestine and Egypt in the second half of the 7th century, in particular the writings of Anastasius of Sinai.