This article explores the volatility of indigenous identity, not as inconsistency or exception but as its central explanatory principle. This research is based on ethnographic and historical examples from Mexico and Latin America. Despite general recognition that "identities are contextual," I show that it is still relevant to dismantle the ontological register associated with identifications, whose philosophical underpinnings might be traced back to Aristotle's theory of classification. As an alternative, I develop an analytical model centered on the elusiveness of identities, based in Ernst Cassirer's theory of classification, for whom classifying means momentarily stabilizing incessantly mobile content. I also draw on theories of ethnicity and in an intellectual history framework to propose three dimensions in which the volatility of identifications can be captured: meanings, configurations, and experiences. I conclude by discussing some of the political consequences of adopting this interpretive model. [categories of identification, collective action, essentialization, indigeneity, indigenous identity] R e s u m e n Este artículo explora la volatilidad de la identidad indígena, no como inconsistencias o excepciones, sino como su principio explicativo central. Esta investigación se basa en ejemplos etnográficos e históricos de México y América Latina. Aunque en general se reconoce que "las identidades son contextuales", muestro que todavía es relevante desmantelar el registro ontológico asociado a las identificaciones, cuyos fundamentos filosóficos se remontan a la teoría de la clasificación de Aristóteles. Como alternativa, desarrollo un modelo analítico centrado en la elusividad de las identidades, basado en la teoría de clasificación de Ernst Cassirer, para quien clasificar significa estabilizar