For 10 points, name this theory positing doubt about our ability to know common-sense things.
Contextualists such as DeRose resolve the problem posed by this theory by claiming standards change with conversational context. Dretske argued against this theory with an example considering whether zebras in a zoo were really mules. That argument against this theory was expanded on by the non-justified-true-belief definition of knowledge in Nozick's tracking theory, in which certain claims track truth but their entailments need not, and so denies the deductive closure principle. One argument against a formulation of this theory used the causal theory of reference to argue that words would refer to objects-in-the-image, and thus this claim couldn't even be properly formulated. The "Here is one hand" argument by Moore was meant to refute this theory with respect to the external world. For 10 points, name this theory positing doubt about our ability to know common-sense things.
Contextualists such as DeRose resolve the problem posed by this theory by claiming standards change with conversational context.
skepticism [accept closure (or more specific forms) before mention; accept idealism after "Here is"; anti-prompt on "brain in a vat"]