What “counts” as reliable data? Nahua science and the tlapohualiztli (reading) of earth and sky

In this article, I explore what “counts” as reliable data in Nahua science by examining how Nahuas systematically perceive and interpret phenomena across earthly and celestial realms. Using sixteenth- and seventeenth-century Nahuatl and Spanish sources, I trace how Nahuas identify signs on the ground and in the sky to diagnose instability and guide collective action. Far from superstition, these interpretive practices form a rigorous analytical tradition based on patterned inference and community consensus. Viewed through Indigenous science frameworks, Nahuas demonstrate a relational way of reading (in the broadest sense) and engaging with the world. Focusing on Nahua methods broadens the understanding of what counts as reliable data, ultimately challenging Eurocentric knowledge hierarchies and promoting a more inclusive view of scientific inquiry.