Ok, some continuing thoughts.
1) I don't contest that it's possible to hold a rational belief in Christianity, and to argue convincingly that your belief is well founded. Of course, there's a wide spectrum of Christian belief, and a lot of it isn't rational - eg. a belief in biblical inerrancy flies in the face of strong evidence.
2) It's certainly possible to argue your way out of belief in Christianity. I seem to have done so.
3) Arguing your way back into a belief seems to require a willful suspension of disbelief. The sticking point is that Christianity doesn't just require you to agree with principles, it requires you to believe in certain facts which are either unfalsifiable, or for which the evidence is at best ambivalent and buried in the past.
1) I'd say that it might be possible to hold some degree of a rational belief in Christianity. Now, can that belief by convincingly argued? I say no. But that doesn't mean you can't still believe in Christianity. It simply means that your belief is rooted in faith. If one is comfortable with faith, they can be Christian or any other religious belief.
2) I'd say it is possible to argue out of any belief due to the first point. And at some point in the argument, invariably, the word faith comes up. Faith cannot be argued. Faith is a decision made by the believer. It is a personal choice.
3) You will find this probably true of any religion. Arguing back in to a religious belief requires belief in things that can't be proven, hence faith.
Thus, I would argue that if religious conversion was based on logical and rational argument, there's little chance of going back to that religion.
I've seen people convert from Christianity to Islam because they viewed God as something that operates on a simple and basic premise, do good, and God rewards. Do bad, and God punishes. And some people like this.
I've seen people convert from Islam to Christianity because they felt God should be more personal and accessible. Just as Kathy argued when she quoted her husband on this thread. Some people like this.
And some deny either religion because, inevitably, they look at the sources and applied logical and rationale arguments. The key is not arguing the principles of the religion, because those principles can work for anyone based on personal preference and you are left inevitably arguing about the very nature of God in that case.
But, if faith is not good enough, then one might be encouraged to look at the source of a religion within historical context, applying logical and rationale arguments and analysis. And belief in a religion via this path is doomed to fail.
This is why faith, I think, is considered a virtue in many religions. Without it, you can't be a believer.
Whereas, in any other activity in society, faith is recognized as lazy and useless. You don't become an accountant because you have faith the numbers will work out. You don't make a good scientist if faith guides your approach to experimentation. An engineer that believes her contraption will work with out evidence (testing it) will find few buyers and/or endanger lives.
But religion answers the questions otherwise unanswerable:
Why are we here?
Where do we go when we die?
Is there a God, and if so, what are His qualities?
Faith will always have a place in this world so long as these questions are conclusively answered by old books written by unverified authors.
Dioptre, if you are comfortable with faith, to whatever degree, then I believe that you can be a believing Christian. Whether or not you want to base your beliefs in faith is up to you. But I see no way you can go back to Christianity by looking for evidence outside of religious texts.
The best evidence ends up being personal experience. Pretty much every KuriousKathy post reinforces this. If faith works for you, go for it.
Dioptre, if you don't feel satisfied with faith, if you want the conclusive evidence for any religion, I am personally not aware of it. Quite the contrary. However, that has been my own personal experience, and should be taken as such.
Good luck.
