This dissertation argues that if we are to respect the common sense perspective then Pyrrhonian scepticism can be neither avoided nor defeated. While Pyrrhonian scepticism can be diagnosed it cannot be cured, at least, so long as we take a non-revisionary attitude towards common sense. The fundamental reason for this is that Pyrrhonian scepticism derives from the application of norms of inquiry that constitute part of the content of common sense in unusual but not fanciful or impossible situations.
Implicit in this dissertation is a distinction between Cartesian and Pyrrhonian scepticisms, and for present purposes these two scepticisms can be distinguished on two criteria. First, unlike Cartesian scepticism, Pyrrhonian scepticism is not global in its doubts. It is not global because it does not attempt to question our entitlement to entire domains of commitment, for instance commitments to anything beyond the content of our perceptions, all at once. Nor does Pyrrhonism attempt to deny the possibility of knowledge. Rather, Pyrrhonian scepticism questions our entitlement to one commitment at a time and is hence iterative rather than global. This leads to the second far more interesting criterion in that unlike its Cartesian cousin Pyrrhonian scepticism claims not to be revisionary of the common sense perspective. In fact Pyrrhonian scepticism represents itself as the common sense perspective under special conditions. On this reading Pyrrhonian scepticism is a form of common sense scepticism.
The claim that Pyrrhonian scepticism is commonsensical calls for a clarification of in what exactly the common sense perspective consists, and its relationship to scepticism. Of particular interest in this regard is a position that has been called Common Sense Naturalism (CSN). CSN consists, in part, in three important claims. First, that we are constrained, both logically and psychologically, to take ourselves to have an entitlement to common sense. Second, that because we are thus constrained, we have an entitlement to those commitments that constitute the content of common sense. Third, that the content of common sense is inherently anti-sceptical. These three claims jointly warrant
the conclusion that appeals to commitments to which we are commonsensically entitled can feature prominently in refutations of scepticism.
I argue that CSN is incorrect in that even if we have an entitlement to our common sense commitments we have an equally valid entitlement to Pyrrhonian scepticism, as Pyrrhonian scepticism can be derived from the common sense perspective itself. I also argue that CSN is correct but misleading in suggesting that we are constrained, both logically and psychologically, to take ourselves to have an entitlement to the content of common sense. CSN is correct in that we are always forced to take ourselves to be entitled to some commonsensical commitments but overlooks the fact that the content of these commitments varies, becoming at times amenable to Pyrrhonian scepticism. In fact what we take to be commonsensical is sensitive to our mood at the time. This can be used to explain that feature of the phenomenology of scepticism according to which Pyrrhonian scepticism is a recurrent but not a constant problem. Presenting these arguments requires both that the nature of CSN be clarified (chapter 1), that the relationship between common sense and Pyrrhonian scepticism be established (Chapter 2). Finally, we must also provide an account of the content of common sense be given (Chapter 3) which provides warrant for continued inquisitive activities even after the emergence of Pyrrhonian scepticism from within common sense.