The article deals with the heuristic potential of early medieval collections of saints' miracles (libri miraculorum, miracula) which are rarely studied in anthropologically oriented historiography, because they are literary fiction and, unlike the 12—17th century miracula, cannot serve as sources for studying folk piety or everyday life. Using the example of St. Willehadi's miracles (Miracula s. Willehadi, 860—865) by Bishop Ansgar of Bremen, the article analyzes the possibility of involving texts considered “unreliable” in terms of the facts described in them, within the framework of the cognitive theory of communication. The approach to the miraculous text as a message containing meaning-generating representations, which have a distinctly expressed communicative intent, allows to reassess its content, which in traditional studies is usually devalued as “hagiographic topics”, and to establish the pragmatic function of the text (causa scribendi), which is not always limited to the proof of the sanctity of the hero.