Dale Matthew, a grad student at York, sent me a case that raises an interesting issue for evidentialists. Here’s the case:
It is the consensus of a scientific community that P. In coming to accept P they used all the available resources (theories, observation equipment, etc.) as best as they could. Further, in coming to accept P they were as epistemically responsible as they could be. In other words, they are blameless all around. But then a genius scientist, Insight, arrives on the scene, and through his sheer brilliance is able to discern that instead of P being true, -P is true. Further, Insight is able to discern that the basis on which the scientific community in question came to accept P made P unlikely to be true, highly improbable in fact. Insight relates his, well, insight to the scientific community and the community promptly recants its acceptance of P. Now was the community justified in accepting P before Insight arrived to save the day?
Notice that it is central to the case that the body of evidence is the same for Insight and the rest of the community; what’s different is the assessment error made by the community and the correction by Insight. Since it’s obvious that such cases can occur and that after being corrected by Insight, the community is no longer justified in accepting P, the evidentialist can’t accept the description that the community was justified before hearing from Insight and also hold that justification is a function of total evidence.
I believe this is the issue that Dale hangs his argument on, though he can correct me if I’m wrong. He’s hoping for responses from blog readers, and I’ll hold off commenting on the issue here in the main post to allow the case and the issue to stand on their own.