The purpose of this paper is to refute the widespread view that challenging a knowledge-claim always raises the original standards of justification–a view often associated with contextualism. To that purpose the distinction between undermining and overriding defeaters will be used. Three kinds of challenges will be considered that differ in their degree of specification. In all three kinds of challenges, the rising standards of justification model fails to capture the dialectic of justification in the case of undermining defeaters. At the (...) end, the skeptical challenge will more briefly be given a similar analysis. (shrink)