The structure of art depends largely on its functions. Various functions have been proposed: entertainment, instruction, the catharsis of unpleasant and unconstructive emotions, imitation and fantasy. Certain artistic structures obviously carry out these purposes. The "theme" or "point" of a work of art clearly expresses the function of instruction; the convention of the "hero", by encouraging audience identification, fulfils the "fantasy" function of art; and the "fourth wall" convention of modern theatre was developed to intensify the effective "imitation" in drama. The main plot and the secondary plot of Henry IV, Part I is discussed along with the musical and symbolic structure.