Consider Williamson-style beliefs that obviously have the property that they have to be correct if they are believed. For instance, if I believe that I have a belief, then that belief is guaranteed to be correct. Call beliefs like this obviously self-guaranteeing.
Suppose now that I am unable to introspect my beliefs and am not a sufficiently good observer to gain evidence as to what I believe on the basis of my behavior. Unsure whether I have any beliefs, but thinking that true beliefs are valuable to have although false ones are valuable to avoid, I try to will myself to believe that I have a belief, because it is clear to me that that claim will be true if I believe it. (You might ask: If I do that, don't I already believe something, namely that the belief will be true if I believe it? Maybe, but that's beside the point, since I am unable to tell that I believe it.) I don't know if I will succeed—and even if I do succeed, I won't know that I have succeeded—since willing myself to have a belief is a notoriously shaky thing. There seems to be nothing incompatible with the love of truth in willing myself to believe that I have a belief, indeed there seems to be nothing epistemically bad. But I am (a) willing myself to believe something I now do not have evidence for, and (b) if I do come to believe it, I will believe it without any evidence for it. If indeed there is nothing epistemically bad here, then (b) gives a counterexample to synchronic evidentialism and (a) gives a counterexample to diachronic evidentialism.
But perhaps there is something perverse here. See tomorrow's post.