In 2003, teachers at the municipal high school in Belmonte, Brazil, began presenting students with a radically different ideology about racial categorization: an essentialized ideology that defines anyone not "purely" branco (white) as negro (black). This system of categorization conflicts with popular belief in a mixed-race moreno identity based not only on ancestry but also on observable physical features. Through a combination of ethnographic and experimental methods, I examine this apparent clash of ideologies in Belmonte with respect to academic theories on the cognition of race and ethnicity. I show how children and adults integrate certain aspects of essentialism but not others in their constructions of identity and in the way they reason about hypothetical scenarios. These nuanced solutions to the challenges posed by explicit conflicts over supposedly natural categories lead to my own questioning of race in anthropological theory.