Reassessing the case for evidential externalism

Let internal twins share ‘the same non-factive mental states to the same degree - the same beliefs, apparent experiences, apparent memories, and so on’ (Silins 2005: 376-377). We can then ask: must internal twins have the same evidence as each other? Following Nicholas Silins, we’ll call an affirmative answer to this question Evidential Internalism and a negative answer Evidential Externalism. Evidential Externalism is not equivalent to the thesis that evidence is factive. One can consistently hold that evidence must be true and that evidence must be shared by internal twins if one holds that one’s evidence consists of true propositions about how things seem to one, for example. So accepting factivity does not suffice to make one an Evidential Externalist. Accepting factivity isn’t necessary either. For example, one might hold that one’s evidence is just what one is non-inferentially justified in believing and have a reliabilist conception of what such justification requires (e.g., Goldman 2009); on such a view, one’s evidence can in principle contain falsehoods, but external differences can make for differences in what evidence twins possess. Nor is Evidential Externalism to be equated with the thesis that in epistemically favourable cases, one can have entailing evidence for propositions about one’s external environment: evidence that entails the truth of the proposition it is evidence for. Again, we can demonstrate the point with appeal to reliabilism; I might not share the same evidence as my internal twin due to differences in our external environments giving rise to differences in the reliability of the methods we each use, but it may additionally be that the best that either of us can hope for is to have evidence for propositions about our environment that makes them very likely to be true without entailing their truth (compare Silins 2005: 399-400, n. 11). That duly noted, the kind of Evidential Externalism that will be our focus here does accept that epistemically successful subjects will have entailing evidence lacked by their less successful internal twins; Silins calls this variety of Evidential Externalism Entailing Evidence Externalism. It is in this sense, then, that we are engaged with the factive turn in epistemology