 For some practitioners, however, the idea that epistemology is a normative discipline means more than this. For example, some think that epistemological terms (or concepts) like ‘knowledge’, ‘evidence’, ‘justification’, ‘duty’ and ‘virtue’ cannot be adequately defined or fully explained in purely non-normative vocabulary (e.g., Axtell &amp; Carter 2008; McDowell 1994; Roberts &amp; Wood 2007; and Zagzebski 1996, 2009), although others disagree (e.g., Goldman 1992; Greco 1999, 2009; Sosa 2007).