If the sceptic holds nothing to be true, his dogmatic opponent argues, he is not able to act. This is the core of the famous Apraxia challenge, arguably the best known anti-sceptical argument in antiquity. Several versions of this argument figure in ancient scepticism. At least for the most part, these arguments rely on core assumptions of Stoic epistemology and theory of action: that we have impressions (phantasiai), some of which are practical, i.e. prescribe an action as to be done, and that we either assent to our impressions or not. In assenting to an impression, we hold something to be true. For fools (i.e. almost everyone), this amounts to having an opinion. For the wise person, every instance of holding something to be true is a piece of knowledge. In the case of practical impressions, assent (sunkatathesis) is further identified with impulse (hormê). If there are no external impediments, impulse sets off action.

The sceptic’s explanation of his actions most importantly consists in his response to the Apraxia challenge, and more particularly, in his critical engagement with the Stoic claim that, in action, we assent and thus hold something to be true. Our interpretation of his response to the Apraxia challenge, however, relates to a broader framework of questions. First, how closely does the sceptic’s life resemble ordinary life? Are the sceptic’s actions, in the end, like everybody’s actions? Secondly, does the sceptic consider his way of life as an attempt at living well? Is suspension of judgement, perhaps, a safer road to happiness than adherence to a (potentially false) philosophical account of what is good and bad?