 Philo’s motivation for his final shift away from skepticism in the Roman Books can be seen, at least in part, from the criticisms directed at him by his ex-student Antiochus before their publication in 88/7 BCE. These criticisms point to a kind of instability inherent in mitigated skepticism: it seems to waver unhealthily between a dogmatic position allowing for something approaching certainty about some questions and a radical skepticism about our ability to make any epistemic progress. More specifically, it suggests that we can take persuasive impressions as evidence for the truth that is firm enough to warrant assent—thus allowing for a life guided by reasoned belief, and even ethical teaching—while simultaneously maintaining that even the most perfect rational consideration of the evidence is compatible with wholesale error. (See the argument in Cicero Ac. 2.111, addressed explicitly to Philo prior to his Roman view, and its elaboration in Ac. 2.34–6 &amp; 2.43–44. These Antiochian criticisms are echoed almost verbatim by Aenesidemus in Photius Library 212 170a 14–38.)