  Sextus himself thought that the Five Modes had universal application: ‘That every object of investigation can be referred to these modes we shall briefly show as follows’ (PH I 169). Unfortunately, what follows (PH I 170–77) is far from clear, and doesn’t take the form one expects, namely the observation that any argument whatsoever must have one of the three forms of hypothesis, reciprocality, or infinite regression. That stretch of text remains mysterious.