In his works on argumentation, Aristotle develops three main forms: apodeictical, dialectical, and rhetorical argumentation; dialectic is subdivided into several subspecies. The purpose of this paper is to discuss all of the forms described by Aristotle, to examine their differences and to point out their interrelations. This leads to an examination of the differentiating criteria and their applicability in the case of each argumentation form—and in particular to the question regarding the number of criteria that are necessary to describe each (...) form clearly and unambiguously. It is argued that Aristotle’s works on argumentation contain an implicit system of argumentation forms that is based on no more than three criteria. (shrink)