This dissertation consists in an analysis of the poetry in the Plato s dialogue The Republic. The proposal that Plato presents for the poetry has a deeply ethical and political motivation. The poetry (myth) is the main component of the first part of an educational process whose objective is to instruct certain class of citizens responsible both for the security guard and the government of the city idealized in the dialogue. In its works, the poets must follow some norms that obey pedagogical criteria. Such norms are needed to get the poetry to contribute positively for the development of a good and beautiful character. The poetical theory is first approached in Books II and III, but, due to a slight knowledge later clarified, its conclusion could only be reached in the end of the dialogue. Therefore, this work defends that Book X is necessary to conclude the determinations for the poetic art, and that there is a sense of continuity linking the propositions presented in the first period to those of the second stage of the poetical criticism. The first part of this work analyzes the arguments defended in Books II and III, in which Plato initiates the construction of the poetical norms paradigm. The second part analyses the conclusion of the considerations about the poetry presented in Book X.