It is an undeniable fact that there are many mutually contradictory religious belief systems, many, if not all of which have devout adherents who claim to have arrived at what they firmly believe to be absolute truth via subjective faith in divine revelation, scripture study and/or prayer.  This is the strongest evidence I can possibly imagine of the inherent unreliability of that approach to discerning any kind of truth whether religious or secular.  Even if one of these mutually contradictory belief systems really is the absolute, divinely revealed truth its adherents believe it to be (which no more than one of them can be), the unreliability of that approach is still solidly established!  Consequently, no conviction or doctrinal claim is more deservedly suspect than one that can only be supported by claiming divine authority for it--no matter who or what claims such authority.

One can justifiably argue, of course, that human reason and judgment are not infallible, and that even with the most honorable intentions (and certainly when dishonorable intentions are involved), occasional errors are inevitable.  However, it is also undeniably true that absolutely nothing more clearly demonstrates the truth of that fact than the abundant nonsense and numerous atrocities that we humans have perpetrated on each other in the guise of religion and in the very name of God!  In fact, it often seems that the more outrageous and nonsensical the claim, the more likely it is that its principal advocates will invoke the claim of divine authority for it.  After all, what else can they do if determined to defend and promote claims that they know will not otherwise survive exposure to objective evidence and critical, honest scrutiny and reason?  This is yet another reason why convictions supported only by subjective, religious faith are highly and deservedly suspect.

It has become increasingly clear to me that one of the silliest notions ever conceived by human minds is the idea that we don't necessarily have to have conclusive, objective evidence for something before concluding that it must be true.  This notion is not the slightest bit less silly in the case of religious or spiritual convictions than it is for secular convictions!