This article takes as its point of departure a discussion of José María Arguedas’s engagement with Marxism, the ideas of José Carlos Mariátegui and the journal Amauta. It argues that Arguedas’s distance from official party politics should not be confused with an abandonment of politics as such. It also underscores Arguedas’s reflections on the relationship between lived experience, socialist theory and literary writing. This sets the stage for an exploration of a core problem in Arguedas’s oeuvre: the missed encounter between Marxist organisations and indigenous communities, which is to say, the failure to form an alliance between these groups based on mutual understanding and reciprocal enrichment. The article turns to Arguedas’s first major novel, Yawar Fiesta (1941), and traces its portrayal of such a missed encounter as it occurs around the celebration of turupukllay, an Andean translation of a Spanish bullfight that commemorates Peru’s independence from colonial rule. The wager of the article is that Yawar Fiesta’s capacity to illuminate key contributing factors of the missed encounter enables Arguedas to advance an immanent critique, a critique of a certain tendency of Marxism from within Marxism itself, and that, as a result, the novel supplements socialist theory by simultaneously exposing its limits and enhancing its claims.