  The second, more pressing difficulty is that, although these premises are adapted to the Arcesilean context in which nothing can be known and the wise person does not assent to anything, they are manifestly variants of the Stoic theory. The Stoics claimed that a good life is the result of performing ‘appropriate actions’—defined as “those that, once done, have a reasonable defense”—from a disposition of wisdom, i.e., knowledge of what is good, bad and neither. But if nothing can be known, as Arcesilaus has already argued ([5]–[7] in sect. 3, above), the wisdom of the sage consists in not having any beliefs. This disposition will still allow the sage to perform appropriate actions, however, if, as the Stoics claim, they are defined by reasonable defenses or justifications. The connection between performing such actions through a wise disposition and success is, Arcesilaus suggests, something that the Stoics can’t deny, because they agree that opinion is the cause of error (this is the justification for premise [6] in sect. 3, above).  Hence, the perfect exercise of our rationality—reflection without assent, as Arcesilaus has argued—will lead us to find the action that is appropriate to us as rational animals, i.e., the reasonable thing to do, and this guarantees success. Arcesilaus therefore employs the Stoic definition of appropriate action to defend acting on views that are reasonably justified. But, for the Stoics, what is reasonably justified is what conforms with the sage’s knowledge of what is good, bad, and neither. Arcesilaus, it seems, cannot borrow his opponents’ theory without also accepting the possibility of knowledge.