Comparing language with money has been customary since Classical Antiquity. The widely held opinion that this topos invariably highlights the conventional nature of language is however a fallacy. First of all, both sides of the comparison are in need of clarification - the theory of the symbols for money is just as problematic as the theory of linguistic signs. Secondly, topoi as a means of argumentation are remarkably flexible and need to be regarded in terms of the state of knowledge at a given time. A detailed introduction examines the significance of the study of topoi as a field of research in that specific area of literary studies concerned with the history of the discipline.