ABSTRACT
The most important skeptical problems and arguments belong to one or the other of two categories. Agrippan problems revolve around the apparent threat of an infinite regress reasons. Cartesian problems, while they sometimes incorporate Agrippan elements, differ from pure Agrippan skepticism in making essential use of skeptical hypotheses. This chapter addresses the anti-skeptical strategy, in Unnatural Doubts and some objections due to Duncan Pritchard. The Cartesian skeptic accepts that doubts need grounds and provides them in the form of skeptical hypotheses. The skeptic's response will be that the scenario is only meant to represent a 'logical' or 'metaphysical' possibility. Wittgenstein's account of knowledge as objective certainty fleshes out the diagnosis of Cartesian skepticism that offered in Unnatural Doubts. According to that diagnosis, the source of the skeptical problem is the idea that "empirical knowledge" answers to a circumstance-independent structure of epistemological priority.
