  Cicero’s interpretation in Academica 2.66–7 &amp; 2.77 faces two problems. The first is that the argument against the existence of cognitive impressions depends on many facets of the epistemological framework of the Stoics. For the conclusion doesn’t follow unless it is true that there are impressions, that some are true, that there are no other routes to cognition, that the Stoic definition of cognition gives necessary and sufficient conditions for knowledge, etc. And there is reason to doubt Cicero’s testimony that Arcesilaus subscribed to these Stoic views, since we have some evidence that he argued against every aspect of Stoic epistemology and psychology. Plutarch, for instance, mentions an objection to the Stoic theory of the soul’s interaction with the body, which implies that Arcesilaus argued against the fundamental mechanism of impression in Zeno’s account (On Common Conceptions 1078c). Another fragment from Plutarch suggests that Arcesilaus argued against Zeno’s causal theory of perception (Fragment 215a). And Sextus reports that Arcesilaus also objected to Zeno’s conception of belief as assent to an impression, on the ground that assent is a matter of reason or thought, rather than the acceptance of a physiological item, the impression (M. 7.154).