“Should I just continue to form opinions and interpretationsMy concern with this approach – and the implicit claim that Catholicism would remove this autonomy – is the fundamental problem that it doesn't recognize that all revealed religion is self-referential and its “own authority”. If we take revealed religion at its word, then the self-referencing authority is a being of some sort. If it’s an all-powerful being, then perhaps that’s reason enough to submit. But the point is, what we’re trying to get at the truth of is precisely the reality of this being. If we’re unwilling to take revealed religion at its word (which presumably we aren’t if we’re asking the question “what is true?” in the first place), then what is self-referencing is the revelation itself. Having lost the author of that revelation we come back to this convert’s initial conundrum: any conclusion based on revelation is going to be a conclusion derived from our own authority, our own interpretation – from ourselves. This is the heart of what it means to have "faith" - it is to trust in your own authority and assessment of something that you have no other evidence for. If you have faith in something someone else told you, then you are authorizing them to provide you with truth, but you are still the source of any authority that you actively or passively ascribe elsewhere (to a text, to a cleric, etc.).
with lots of prayer and reflection? Should I just do my best to be part of the
group I feel conforms most closely with Scripture? No, I can't because any
options within this paradigm of Sola Scriptura lead to the same fateful
conclusion that I am my own authority.”
Standard Epistemological Foundation 1: Rationality
Traditionally, standards of what is considered "knowledge" have had to be based on more external foundations. We derive knowledge logically that is indeed contingent knowledge, but it is still independent contingent knowledge. Given a set of axioms and given a set of rules, we say that a deduction is true. This knowledge is contingent on these givens, but it is independent insofar as (1.) the axioms are not argued from authority, but from consensus and mutual agreement, and (2.) there is consensus and mutual agreement on the rules of logic. Nobody can assert axioms or rules on his own authority or on the authority of some magisterium. Moreover, the useful knowledge that we derive in this way is derived. We don't consider the axiom itself to be useful knowledge so much as tautological or definitional knowledge. In Real Analysis, you start with the "field axioms" - all the various real number properties, the existence of the additive identity, the existence of the additive inverse, etc.. Likewise, we axiomatically claim things like "all bachelors are unmarried". The claims of revealed religion (authority of scripture, apostolic succession, reality of God) are treated as axiomatic in this sense (and we can think of theology as the body of knowledge derived from these axioms), but there is a problem with this. Axiomatic claims are supposed to be simple, basic, tautological or definitional if possible, and a starting point of broad agreement and concurrence. Or, if not broadly agreed upon at least useful assumptions (neoclassical economics, for example, is built up from some dubious axioms that we explicitly assume - but then the conclusions we derive are tested for veracity).
With revealed religion or theology, the axiomatic presupposition is in fact exactly what we want to prove! God is assumed. The authority of scripture is assumed. And details are derived from there. This, of course, is backwards. It's a way of churning out volumes of doctrine, but it's not a way to find assurance of the most important questions: is there a God? and has He interacted with us? These important questions are just asserted and the less important questions are the ones that are derived or proven (if we choose to think of the tenets of a faith as axiomatic).
Standard Epistemological Foundation 2: Empiricism
Another epistemologically valid option is inference from empirical observation. This doesn't necessarily have to be rigorous if we're willing to attach an element of doubt. In other words, we can make valuable, useful inferences about the nature of water fowl without strict falsification if we keep in mind the possibility of a black swan. "Almost all swans seem to be white, but I guess there could always be a black one" is a piece of knowledge that we can work with and use in every day life, that is based on empirical evidence, even if it is weaker than the definitive "all swans are white". Revealed religion isn't based on this form of knowledge either. To the extent that people cite empirical evidence, it is exceedingly vague. It is a feeling or an intuition. For a moment we can put aside everything we know about brain chemistry and moments of euphoria, and simply observe that even if this intuition or feeling is genuine, it can't be conclusively attributed. Did it come from the Holy Spirit? Or did it come from Allah? Even assuming that it is a genuine external force acting on us, how do we have any confidence in attribution? Often, the confidence for believers comes from corroboration. An intuition is consistent with Scripture, for example ("test the spirits"). But what value is it to be consistent with Scripture? Again, the authority of Scripture is ascribed (either by oneself or by an institution to whom one attributes authority), not inherent. What revealed religion does is take a prefabricated understanding of the universe and overlays that on top of feelings and intuitions that on their own could not be ascribed to any source. There is something that objectively exists - a feeling, an intuition. That's not the problem and the observation of that feeling or intuition is not the problem. The problem comes from what sort of knowledge is derived from it. To put it in swan terms, revealed religion says "I see many, many white swans and I conclude that the white swans are black swans that have painted themselves white". The problem here isn't the observation per se (the observed white swans are analagous to the spiritual feelings or intuitions that I'm not trying to deny happen) - it is the fact that every important element of the knowledge that we try to derive from these feelings and intuitions is brought to the experience or speculated, and not inherent in the experience itself. Approaching our knowledge of revealed religion as an empirical endeavor is problematic for much the same reason that approaching it as a rational endeavor is: every informational contribution that meets epistemological standards (either rational or empirical) is vague and unattributable to any god, much less a specific god; every informational contribution that provides clarity, specificity, and significance is information that is assumed or self-referential.
This is all obviously extremely problematic. We like to think that the strength of an argument for the truth of a claim should be proportional to the significance of the claim we are making. "I am the Son of the one true God and I have come to Earth to be sacrificed, an act which will absolve your sins" presumably requires considerably more evidence than "the sky is blue". A casual, unscientific empiricism suffices for the latter. And yet the former many of us treat as axiomatic! Why? How? Scripture? That just regresses the problem back one step - what is the authority of Scripture? That too is axiomatic. The convert from Presbyterianism to Catholicism cited earlier is concerned with the shakiness of this step back to Scripture. His solution? The magisterium! But from whence does the magisterium derive its authority? God. And how do we know the magisterium derived its authority from God? Two ways: Scripture and that the magisterium told us so! It's all axiomatic! And unlike definitional axioms like the associative property or “all bachelors are unmarried”, these axioms are complex, specific, and ultimately precisely the points that we wanted to verify!
This may sound harsh to revealed religion, but it shouldn’t be understood that way. What I’m being harsh with are the claims of individuals who make inappropriate claims for revealed religion. Ultimately where all this leads us to is the self. Belief in revealed religion is belief in something that you authorize yourself to consider “true,” not belief in something that any established epistemological standard (either rational or empirical) allows you to claim is true. In terms of the truth-claims of revealed religion all authority is vested in the believer. Now, if those claims are indeed true, then perhaps other types of authority reside elsewhere – perhaps with God. But the claim itself by the believer is made on the authority of the believer. And that believer may delegate authority to a text or to a cleric or to a magisterium. This is what faith is – it is the self-authorization to believe something that you have no justification for believing aside from your own self-authorization to believe it (of course we can mix faith and evidence. I can say “I have faith that my wife won’t cheat on me”, which is based on observational evidence of her past behavior as well as a hope that I authorize myself to maintain for sentimental reasons, or just to keep myself sane).
Being serious and honest about the epistemological problems with revealed religion actually reinforces a lot of what (at least Christianity – particularly Protestant Christianity) has to say about itself. Whether faith is a wise choice is another question entirely, and I’m not even sure how one would answer that question.
I’d conclude with another hesitation – the point that what we are trying to understand here (the existence and nature of God) by definition eludes epistemologically sound verification. We are talking about an invisible or spiritual being that wants to let humans have a substantial degree of free will and free reign. It is a singular being supposedly – we don’t have lots of them to compare and look at, as we do with the classic case of the swans. It is a being that withholds judgment for quite a while. It is a being that said his piece two millennia ago and let a Spirit take the initiative from there. This is a being which, if we were trying to pursue empirically, we would not expect to get very far with. The noise swamps the signal. The appropriate response to this situation isn’t to declare its non-existence, but to say that we “fail to reject the null hypothesis”. We can’t make a claim one way or another, but we do declare that we are unable to embrace the affirmative.