The two treatises are companion pieces and each refers to the other. The Poetics analyses how tragedy produces its effect on an audience; the Rhetoric analyses how a speaker produces an effect on one. They share a vocabulary and a method, and the discussion of style and diction in the third book of the Rhetoric points back to the Poetics directly. Taken together they are the foundation of the European tradition of treating persuasion and dramatic structure as craft with describable rules, rather than as inspiration.