This study examines the question of how linguistic categories may influence thinking, with respect to the perception of time. Investigating the verb system of Navajo, the author determines that the notion of aspect is crucial; she describes one category, the Progressive, as it is used in various types of discourse. She concludes that, as studies of color terms and perception have shown, no direct link can be established between language categories and ways of perceiving the world, and yet there exist -idealized cognitive models- which suggest important differences between linguistic groups."