 The resolution of these questions depends primarily on an interpretation of Cicero’s Academica, our principal, and only first-hand, philosophical source for Academic skepticism. But this text strongly suggests Philo held three epistemological positions over his career, since Cicero identifies and distinguishes three positions held by different Academics in Philo’s lifetime: a radical skepticism associated with Clitomachus (e.g., in Ac. 2.78, 2.108); a form of mitigated skepticism held by a group of Academics who regarded it as incompatible with the Roman Books (Ac. 2.148, 2.11–12 &amp; 2.18); and the Roman Book view (Ac. 2.18). So it is clear that the Roman Books did represent a third distinct Academic position. It also seems clear that they represented Philo’s third epistemological view, because the interpretation of Carneades that generated the second view is explicitly tied to Philo and Metrodorus (Ac. 2.78, cf. 2.148), while we know that the Roman Books offered a novel interpretation of Arcesilaus and Carneades that was contested by the proponents of the second view (Ac. 2.11–12, 2.18). We can thus safely infer, in response to the first question above, that Philo advocated mitigated skepticism at some point in the 90s BCE, prior to the Roman Books of 88 BCE and after his election to the scholarchate as a Clitomachian radical skeptic in 110/9 BCE. That this is correct is confirmed by the criticisms of mitigated skepticism aimed at Philo by his student Antiochus before the Roman Books (see  section 3.4  below), and by the fact that virtually all the generic references to Academic skepticism in later writers assume that it was a form of mitigated skepticism (see, e.g., Gellius Attic Nights 11.5.8, Photius Library 212.170a, Plutarch Stoic Contradictions ch. 10, and Sextus Outlines of Skepticism [PH] 1.226–31). Since Metrodorus was regarded as unorthodox, the only plausible candidate for the creation of this received view of Academic skepticism is a work by Philo from the 90s BCE.