Abstract

In this thesis I am concerned to give a characterization of the nature of the sceptical challenge to the possibility of knowledge, as well as to assess the success of one particular way--the so-called best case scenario--of motivating that challenge. ;In Part I, I distinguish between two ways in which a demand for justification can be treated. By considering a range of quite detailed cases I provide a general account of how particular claims to know are called into question in particular practical contexts. This treatment of a demand for justification I call the ordinary treatment. Next, by following closely Descartes' "First Meditation" and, in particular, his use of dreaming as a ground for doubt, I argue that though the sceptic appropriates the structure of justificatory demand and reply embodied in practical life a new type of ground for doubt is, so to speak, plugged into that structure. I argue that unlike the grounds for doubt that motivate ordinary demands for justification, the sceptic's ground for doubt must be raised independent of the contextually articulated and detectable features of any particular practical context. This treatment of demand for justification I call the extraordinary treatment. Finally, in the discussion of the ordinary and extraordinary treatments I develop two technical measures--coherence and relevance--for assessing the sceptic's ground for doubt. I argue that a sceptical challenge to the possibility of knowledge stands motivated if and only if dreaming as a context-independent ground for doubt is a coherent and relevant ground for doubt. ;In Part II, I take up the task of assessing the coherence and relevance of the sceptic's ground for doubt by considering in some detail the best case development of the sceptical challenge. I argue that substantial worries can be generated about both the coherence and relevance of dreaming as a context-independent ground for doubt. I conclude that the best case fails to motivate a sceptical challenge to the possibility of knowledge