In his introduction of intentionality to the focus of philosophical psychology, Franz Brentano made a passing mention of the medieval theory of intentional inexistence as an important precursor. Several historians of ancient and medieval philosophy have since argued that Arabic philosophers, Avicenna and Averroes in particular, played a crucial role in the formation of that theory by introducing the technical term ma‘nā, which was then translated to Latin as intentio. In the present paper, I want to adopt a strategy that, instead of focusing on the history of terms and concepts, takes its cue from one of the phenomena characteristic of intentionality. More precisely, I will ask how Avicenna explains the fact that our mental states can both refer and fail to refer veridically to the world. This requires a two-tiered approach. First, I will study Avicenna’s logical and epistemological treatises with a view to the questions of how he conceives of the intentional relation between our mental states and their extramental referents, and how he makes room for error in that relation. Having laid this foundation, I turn to investigate his cognitive psychology in order to sketch the psychological underpinnings of the semantic and epistemic framework.