Why is it that people are often inclined to accept irrational arguments or to reject rational ones? It is, the author argues, because discussions in everyday life are both dialectical - conducted with the best possible solution in mind - and rhetorical - organized by the interactors in the form of a discursive event. By combining argumentation theoretical and discourse analytical insights and revisiting ancient and medieval rhetoric and dialectics, this study transcends the assumption of a symmetrical communicative situation in which only -good- arguments matter. It redefines dialectical concepts, e.g., acceptability or conclusiveness, from a rhetorical and dialogic perspective and is thereby able to address colloquial speech arguing as the inherently asymmetrical discursive event it is."