Apología del aventurero is the title of a book that José Carlos Mariátegui, the important Peruvian Marxist thinker, intended to write. In spite of his inexhaustible capacity for work and permanent intellectual production, the project was frustrated due to his premature death. The present work offers the reader an original portrait and a new reading of his writings and his thoughts, analyzing the trajectory of this influential thinker in the light of the social reality of the 20th century period in the history of Peru known as "the Aristocratic Republic".