In literature, genre has been known as an intangible taxonomy. This taxonomy implies a concept of containment or that an idea will be stable forever. The earliest recorded systems of genre in Western history can be traced back to Plato and Aristotle. Gérard Genette, a French literary theorist and author of "The Architext", describes Plato as creating three Imitational genres: dramatic dialogue, pure narrative, and epic (a mixture of dialogue and narrative). Lyric poetry, the fourth and final type of Greek literature, was excluded by Plato as a non-mimetic mode. Aristotle later revised Plato's system by eliminating the pure narrative as a viable mode and distinguishing by two additional criteria: the object to be imitated, as objects could be either superior or inferior, and the medium of presentation such as words, gestures or verse. Essentially, the three categories of mode, object, and medium can be visualized along an XYZ axis.