 With Arcesilaus (316/5–241/0 BCE) and his role as leader of the Academy (266/268 BCE), Plato’s Academy turns skeptical. Arcesilaus does not refer to himself as a skeptic—this nomenclature is a later designation. However, Arcesilaus stands at the beginning of a re-orientation in the history of Platonically inspired philosophy. He rediscovers Socrates the examiner, arguably based on his reading of Plato’s dialogues (Thorsrud 2018). Socrates’ commitment to investigation, to the testing and exploring of one’s own and others’ beliefs, and his passion for weeding out falsehoods, are the starting-points of his Academic skepticism (Cicero, Acad. 2.74, 1.46). Throughout the history of this skeptical school, these traits, and the corresponding commitment to a life guided by reason, remain alive (Cooper 2004b, Vogt 2013). When, as we shall see below, Arcesilaus defends a skeptical life without belief, this is because, as he thinks, reason itself, if properly and faithfully followed, leads us to live that way. To Arcesilaus, the skeptical life is a life lived following reason, a life based on reason—just as the competing Stoic and Epicurean lives are alleged by their proponents to be. Arcesilaus engages with the epistemologies of these contemporaries of his. In particular, the Academics call into question that there is a criterion of truth, as both Epicureans and Stoics, beginning in the generation before Arcesilaus, claim there is. One interpretive question that concerns Arcesilaus, but also later Academic skeptics, is especially vexed. According to Seneca (Letter 88, 44), the Academics paradoxically claim to know that nothing can be known. Scholars disagree on how this and similar reports fit together with the picture of Academic skeptics as open-minded inquirers (Allen 2017). According to Sextus Empiricus, the Academics skeptics say that everything is inapprehensible (PH 1.226, cf. PH 1.3). Is “everything is inapprehensible” the single thing that can be apprehended? Does so-called “non-apprehension” (akatalêpsia) amount to the general claim that there is no knowledge? Alternatively, the Academics may dialectically appeal to the Stoic notion of katalêpsis, and argue merely that the Stoic notion of apprehension is not compelling (Allen 2022).