Why is it a “theory” of story? Why not a “model” or a “paradigm”?
Dramatica is different from most of the story models proposed by other writing gurus. Many writing "systems" attempt to classify patterns in stories and give those patterns names. Dramatica takes this process several steps further: Dramatica's theory looks at deep structure, and proposes that the patterns of plot, theme, character, and genre that we see expressed in stories are interconnected . Dramatica tries to explain why these patterns might exist, and tries to postulate which patterns are compatible with other patterns.
Dramatica is a theory much in the same vein as other theories of story, such as deconstruction, semiotics, reader reception, structuralism, et al. So although Dramatica's patterns are compelling, it's difficult to prove them true with absolute certainty.