This paper seeks to elucidate the distinctive nature of the rational impression on its own terms, asking precisely what it means for the Stoics to define logikē phantasia as an impression whose content is expressible in language. I argue first that impression, generically, is direct and reflexive awareness of the world, the way animals get information about their surroundings. Then, that the rational impression, specifically, is inherently conceptual, inferential, and linguistic, i.e. thick with propositional content, the way humans receive incoming information from the world. When we suspend certain contemporary assumptions about propositional content, the textual evidence can be taken at face value to reveal why, for the Stoics, rational impressions are called thoughts (noēseis) and how the Stoics’ novel semantic entities called lekta (roughly, the meanings of our words) depend on rational impressions for their subsistence.