Oh, that’s simple. Looking at most religions which are strongly defined religions*, we really have only the Abrahamic faiths.
Now, with regards to Christianity, I believe its claim is by far the strongest. It includes everything of consequence in Judaism. Its miracles were seen and attested to by hundreds, and have continued to be (false ones, and general idiots notwithstanding). We have a clear record carried down to the present day about a Man who was not just a Man.
I did consider Islam closely. I eventually had to reject it, however, because Islam, even the relatively kindly version we have here, was itself the rejection of human reason in favor of, well, blind fanaticism. Secondly, I have extreme doubts about the validity of the Koran/Qur’an. Not only are certain passages highly suspect (it’s fascinating to see how Muhammed’s opinion of the Jews changed with whether or not he could borrow cash from them), but the whole text has been pretty definitely pinned down to a corruption of a Gnostic or Nestorian bible. (I think).
It is possible that the religion had a truly holy foundation, but it was twisted by someone very early on, possibly Muhammed himself.
Continuing on, we have Buddhism. Let’s seee… original form of Buddhism. I disagree with some of ist priciples slightly, but more or less it’s a philosophical concept and does not in the least contradict Christianity. I would contest its modern Chinese-religious form.
*Now for that little star. There are many religions, such as Shinto, were are highly sectional and really dont’ even claim to be valid outside of their “home-turf” and which are more ritual and myth than belief or faith. Likewise the Norse or Greco-Roman Pantheism. Hindu has a special place in my heart, although it is really not much different.
Not back to Christianity. I looked at Protestantism. I think it is sectionalism, and frankly that breaking the Church any way at all is morally wrong. more to the point, none of the Protestant Particular Churches can stand for all Christianity, everywhere:ironically, they make too strong a claim for understandding things (or once did, anyway). I could go for Orthodox, but I do accept Papal Succession.


