In the Timaeus, Plato famously acknowledges the receptacle as extremely difficult to comprehend. It is neither intelligible (which is reserved exclusively for the Forms) nor sense-perceptible (as it is a principle far too basic). Instead, as Plato proposes, the receptacle can only be apprehended through a “bastard” sort of “reasoning” (νόθος λογισμός, Tim. 52b1-2.). This paper explores an exegesis of Plato’s claim as offered by Calcidius, the 4th century translator of and commentator on the Timaeus. I identify two distinctive methods (...) Calcidius advances when grappling with the knowability of the material substratum that underpins our world. The first method – analysis (resolutio) – traces its intellectual lineage to earlier philosophical tradition, and Calcidius primarily uses it to uncover the proper nature and ontological characteristics of matter. Conversely, the second method corresponds to the only cognitive grasp of matter Calcidius believes humans are capable of. In his view, we can neither sense-perceive nor rationally understand matter. Instead, matter yields itself only to the cognitive mode of suspicion (suspicio). The paper provides a detailed analysis of Calcidius’ suspicio, delving into its intricacies and exploring the interrelationships between suspicio and resolutio. As such it offers a pioneering and comprehensive exploration of Calcidius’ account of the knowability of matter. (shrink)