An untimely, cursed, and anti-modern author, even before the publication of Les Fleurs du Mal, Baudelaire had already made a name for himself among his contemporaries as a perceptive and formidable critic. His interests encompassed all artistic manifestations, from music to aesthetics, including literature, art, and translation. This volume brings together for the first time in Spanish his entire writings on aesthetics, which include not only such representative works as those dedicated to the Salons of 1845 and 1846 and The Painter of Modern Life, but also articles published in the French press, the prologues to translations of Poe, and the study he dedicated to the work of Wagner. All of these illustrate his artistic, literary, and musical thought, and the practice of criticism as a subjective and vehement task, aimed at proposing well-founded and unique perspectives. The texts we present today traced the roadmap of modernity and restore for the contemporary reader a current conception of the aesthetic phenomenon that transcends the confines of the arts to fully embrace the new.