This article shows that the Rhodian model of metatheory can be successfully applied to nonformal systems of a methodological rather than an axiological nature if the demands of the model are satisfied. This requires that we take into account the possible variations of Rhodian models of argumentation and choose the most effective of them. Plato's model of meta-argumentation is only applicable to fields of argumentation that are completely formalized and could be presented as whole general theories.