Abstract
Since its birth at the end of the 16th century, many theories have been written about opera from a historical, poetic, musicological, aesthetic, political and other points of view. However, there has been no systematic attempt to organize these theories and to ask the more basic question: what is opera? We will show that the term “opera” responds to a philosophical idea, beyond any positive discipline. In fact, there is no one idea of opera, but several, some of them contradictory to each other. In this article we present a typology of ideas attending to three logical criteria, which we have obtained after analyzing the materials themselves: the subject/object distinction, the synchronic/diachronic distinction and the singular/plural distinction. This teaches us a lot about our understanding of opera, but it also forces us to ask ourselves if these ideas are adequate to understand the genre.