
Richard F. answered 10/27/21
Cornell Ph.D with teaching experience from MS/HS through Ph.D.
There's a lot to say here but I'll stick to one thing: it raises the q whether there can really be such a thing as purely private evidence.
I can be (now) the only person who knows that Dr. X stole the necklace, but this ordinary kind of case assumes that we understand what it would be for me to share my evidence and have others judge it good or bad. If we instead try to describe the case as one in which my evidence is in some sense inherently private, then it becomes unclear how this is ever evidence - crucially, not just for those others who can never access it, but also for me, who can never have any means for responding convincingly to the claim (say) "you were just hallucinating." (I might feel convinced I'm not hallucinating. But what's my external evidence that I'm not?)
This is essentially the point of Wittgenstein's private language argument: he says there actually can't be a genuinely private language, because attaching meaning to things is necessarily a business of sharing and comparison.
Notice this: I haven't said God can't be offering private evidence of His existence to some and not others. But it would be a weird thing for Him to do, since if Wittgenstein is right it's not just others, but me too, who has a reason not to believe that my experience should count as evidence in this case.