 The Academics attacked every part of this Stoic theory—their practice was to argue against all philosophical positions—but their criticism focused, unsurprisingly, on the central notion of the cognitive impression. The Stoics standardly defined a cognitive impression as one that came from what is, was stamped and impressed exactly in accordance with it, and was, accordingly, such that it couldn’t be false (see, e.g., Sextus Adversus Mathematicos [ M] 7.248 or Cicero Ac. 2.77). They took this to mean, roughly, that an impression is cognitive if and only if