‘Extraordinary claims require extraordinary evidence’, is false. Any claim requires exactly one thing: sufficient evidence. The problem is that people would rather be impressed by something extraordinary than convinced by something sufficient. Sufficient evidence may be dull, ordinary, commonplace, not very impressive, but if it’s sufficient, then that’s all that is needed. Of course, evidence may be spectacular, jaw-dropping, amazing – but these factors have nothing to do with the sufficiency qua sufficiency . The problem, as I said, is that people conflate and confuse being convinced with being impressed, and take the latter to be the former. This is sloppy thinking.
The central thrust of properly basic beliefs ( a theory of knowledge developed by in part by Alvin Plantinga, referred to has PBB from here on out) is that there are certain things (God, other minds, the past) that do not require evidence to be rationally believed in. They can be believed in the properly basic way – to believe otherwise would seem to indicate some cognitive dissonance. This seems to be the case – to not believe that the past happened because of a lack of convincing argument would indeed seem to be odd.
Is this self-defeating, however? If I claim that I don’t need evidence to believe in, say, God, because I can believe in things like other minds, the past, etc, that’s giving evidence that I don’t need evidence.
Or, perhaps, this is a more helpful way of thinking of it: PBB says that evidentialism is wrong – but surely it says this on the basis of evidence. This seems to me to be a bit self-defeating. Can one say on the basis of evidence that evidentialism is wrong? If it’s not self-defeating, it certainly seems suspicious.
But perhaps PBB says something true: it says that on the basis of evidence, evidentialism is wrong – evidentialism cannot justify all our beliefs in a non-circular way. It is evidently true that evidentialism is wrong. If something is self-evidently wrong, then one is not unjustified to call it wrong on the basis of its self-evidence.
So on the basis of evidentialisms self-evident falsity, PBB can claim that evidentialism is indeed false without that claim being a case of self-defeat. It is not self-defeating for PBB to claim that evidentialism is false on account of its self-evident falsity.