A Moorean fact, in the words of the late David Lewis, is ‘one of those things that we know better than we know the premises of any philosophical argument to the contrary’. Lewis opens his seminal paper ‘Elusive Knowledge’ with the following declaration.

Some metaphysicians believe that existence debates are easily resolved by trivial inferences from Moorean premises. This paper considers how the introduction of negative Moorean facts—negative existentials that command Moorean certainty—complicates this picture. In particular, it shows how such facts, when combined with certain plausible metaontological principles, generate a puzzle that commits the proponents of this method to a contradiction.

This paper argues that we should reject G. E. Moore’s anti-skeptical argument as it is presented in “Proof of an External World.” However, the reason I offer is different from traditional objections. A proper understanding of Moore’s “proof” requires paying attention to an important distinction between two forms of skepticism. I call these Ontological Skepticism and Epistemic Skepticism. The former is skepticism about the ontological status of fundamental reality, while the latter is skepticism about our empirical knowledge. Philosophers often assume (...) that Moore’s response to “external world skepticism” deals exclusively with the former, not the latter. But this is a mistake. I shall argue that Moore’s anti-skeptical argument targets an ontological form of skepticism. Thus, the conclusion is an ontological claim about fundamental reality, while the premises are epistemic claims. If this is correct, then the conclusion outstrips the scope of its premises and proves too much. (shrink)