  The third doctrine we might ascribe to Arcesilaus on the basis of his sources is a so-called practical criterion, i.e., a theory that makes action without assent possible (see [iii] in sect. 2).  Arcesilaus’ argument for a ‘practical criterion’ responds to two Stoic objections of ‘inaction’ (apraxia). The first, found in Plutarch, is that action is impossible without assent, since action is caused by assent to an impression of something suited to the agent’s nature, i.e., ‘oikeion’ (Against Colotes 1122a–d; cf. Cicero Academica 2.37–8). The second objection, reported by Sextus, is that a good or successful life is impossible without assent, since a good life requires action based on knowledge of what is good and bad, and hence assent (M. 7.158; cf. Cicero Academica 2.39). Arcesilaus’ reported replies to these objections are brief, and accordingly difficult to interpret (see Bett 1989). His counter to the first objection is the suggestion that action is possible without assent, since even on the Stoic account animal action is triggered directly by their impressions of something oikeion: the addition of assent, and so a belief that the object is in fact naturally suited to the agent, is redundant and liable to be a cause of error. In response to the second objection, Arcesilaus argued that the person who suspends assent universally will successfully guide their actions in light of their sense of what is ‘reasonable’ (‘eulogon’).