 Sextus tells us that the distinctively Skeptical ability is the one which enables its possessor to set out oppositions of such a sort that suspension of judgment ensues (tranquillity, we learn later, will follow  ‘fortuitously’—see 3.3 below).  The sort of opposition which will achieve this is one where ‘none of the conflicting accounts takes precedence over any other as being more convincing’ (I 10) (this is the elucidation of ‘equipollent’). So, a Skeptic is someone who has the ability to find, for any given argument in favour of a proposition P, a conflicting argument (i.e., one whose conclusion is a proposition which cannot be true together with P—call it P*) which is equally convincing.