Nearly every variety of ancient skepticism includes a thesis about our epistemic limitations and a thesis about suspending judgment. The two most frequently made objections to skepticism target these theses. The first is that the skeptic's commitment to our epistemic limitations is inconsistent.
He cannot consistently claim to know, for example, that knowledge is not possible; neither can he consistently claim that we should suspend judgment regarding all matters insofar as this claim is itself a judgment.
Either such claims will refute themselves, since they fall under their own scope, or the skeptic will have to make an apparently arbitrary exemption.