From this discussion.
But the most damning problem with Clifford's thesis is this:
Whatever criterion is used to measure the sufficiency or insufficiency of "evidence", by the very nature of the case, it is not something that is susceptible to evidential verification. Rather, such criterion are "brute" principles by which we must assess the adequacy or inadequacy of evidence. It [first principles] cannot be "proven". Therefore, Clifford's approach is self-stultifying and/or incoherent.
Consider Clifford's statement:
"It is wrong always, and everywhere, and for anyone, to believe anything upon insufficient evidence."
Question: how does Clifford prove his own statement? What does he mean by "wrong"? Are ethical principles the sorts of things that can be scientifically verifiable? Are the methods and principles of science, themselves, scientifically/empirically verifiable?
"Should one say that Knowledge is founded on demonstration by a process of reasoning, let him hear that first principles are incapable of demonstration; for they are known neither by art nor sagacity."
St. Clement of Alexandria in his "Stromata" Bk. II; Ch. IV.