I'll try to be a bit less verbose this time. First I'll finish my response, and then I'll attempt a summary of my points.
You may feel equally confident about the stability of the ground beneath your feet and the truth of the Resurrection, but the former is subject to constant experiential confirmation in a way that the latter is not; subjective certainty does not establish objective truth.
But just because you've demonstrated that the ground has been stable for your entire life doesn't mean it must continue to be. We can reasonably expect it to, certainly, but, to Chesterton's point, that doesn't mean that it must. I don't wish to be overly pedantic, yet the logic behind perpetual continuation of the common place escapes me. Believing such should, I insist, be chalked up to a minuscule, but again, entirely reasonable, bit of faith.
Second, by definition, a historical occurrence cannot be retested; but that does not mean it cannot be falsified. Would it be rational to dismiss the theory of evolution--as applied from apes to man--simply because we cannot repeatedly test it? To reiterate, I accept the Resurrection because I believe it happened. Were it falsified, I couldn't help but disbelieve it.
Catholicism, I continue to maintain, requires an arbitrary and irrational assent to external authority.
I'd disagree, naturally. If God exists, and if God became man in the person of Jesus Christ, and if Christ imbued the Catholic Church with his Holy Spirit to guide it lo these many years, the assent is neither arbitrary nor irrational. Of course, disagreeing with any one of these premises breaks the chain of rationality, but if they are accepted, the synthesis is cogent.
I would add, too, that the apparent absurdity become easier to accept and even understand with a little bit of natural theology. As Augustine put it, "I believe, in order to understand; and I understand, the better to believe." Specifically worth studying is the Catholic doctrine of the simplicity of God, which Aquinas deals with in the third question of his Summa, expounding thereon with the next several questions.
Although I agree that Catholicism has effectively served many of its adherents as a map in the way Chesterton so eloquently describes, the world that it depicts is no longer the world in which we live, which is home to a diverse array of incompatible religious and secular traditions.
In what ways has the world changed? Human nature doesn't change, which is why Catholic doctrine always and everywhere applies. The just war doctrine wasn't made only to serve contemporaries of Augustine, and thank goodness. We would have done much better had our leaders recognized the permanent things, rather than insisting that" 9/11 changed everything".
Competing claims deserve to be entertained to determine their validity, but that doesn't mean that some claims aren't true. Now, again, you can pronounce the Catholic Church wrong on any variety of issues, but it's not because the world is always changing. If it were, no system of ethics would be of any use.
Right now it looks like what would be most helpful for me to do is (1) to offer some kind of naturalistic account for the existence of religion, (2) to provide some examples of what I think Christianity gets right and wrong, and (3) to sketch a secular ethics.
If you would be so kind, with the following amendments. Anyone can come up with a reasonable hypothesis for the rise of religion. On this point, I'd prefer if you could discuss the Catholic faith, which I hold to be unique among religions--with all due apologies to my heretical protestant brethren as well as those from the various orthodox churches of the east. On the third point, if you could concentrate on the reasons one would follow an ethical system, I would appreciate it. I'm reasonably familiar with most of the ethical systems, so we need not get too heavy into Kant for instance. Thanks!
To summarize, I maintain that the Catholic Church's claim to be sole guardian of universal truth to be thoroughly convincing. Once it's premises are accepted, it offers a consistent framework in which and by which to live, as well as a reason--avoiding hellfire for starters, but better still, desiring to please God who is all good--for behaving ethically. Many systems of ethics exist, but while the atheist can point out the utility of certain ethics, and he can even live an exemplary moral life, he can give no reason for doing so.
I further maintain that the person of Christ, and the Catholic Church--which He founded--are unique. The rise of the small cult in the backwaters of the Roman Empire is without precedent in human history. (I can offer an explanation for Islam if you wish me to do so.) The consistency with which the Church has promulgated doctrine is similarly inexplainable without accepting her claims.
Lastly, miracles deserve to be investigated with as much honesty and as much skepticism as we would take any claim from a reasonably mentally stable person. Explanations which evade science do not "prove" miracles, but they suggest the distinct possibility of the existence of the supernatural.
I look forward to your reply.