Fittingly, perhaps, it was the story of the Original Sin which did it.
That was my third (or possibly fourth - long ago, gentle reader, and I didn't keep a diary) year at a Catholic secondary school in the English town where my father had decided to finish out his career with the USAF. (Both my parents held dual Irish and American citizenships, so there was no barrier to his retiring there.)
Prior to that I had experienced only secular American schools on various Air Force bases, and the change had actually made me rather devout. I was even an altar boy (and no, I was never sexually abused, nor to the best of my knowledge were any of the other boys). Even more significantly, now that I was taking Religious Education classes I began to read the Bible thoroughly, and apply a great deal of thought to what I read. That, and a dab of the deadly sin Pride, were to be the beginning of my downfall or liberation, depending on your point of view.
The story of the Original Sin, the Fall from Grace, was a natural fit for a class full of gawky adolescents struggling with puberty, I suppose. It was the first subject for which we were required to write a lengthy essay expressing our own thinking on a religious matter, and we were to concentrate on how it related to our own onrushing adulthood.
As it happened the subject was one I'd already been worrying at outside of class, because something about the story bothered me. What bothered me was this: Adam and Eve (and all their descendants, which also bothered me but that's another story) were punished for disobeying God. That was the Original Sin. This is the fundamental story of humanity's relationship to God, and it seemed to me then, and still seems to me now, that there's a gaping hole in the narrative logic which I have never seen addressed.
My concern was this: We were told that Adam and Eve were given the choice between good and evil, and chose evil by disobeying God... but at the time they did not know good from evil, not having eaten of the Tree of Knowledge of Good and Evil, so how could they possibly know it was evil to disobey God?
It seemed utterly wrong to me, because we were otherwise told that sin follows the intent - that to consider adultery was to have committed it, for example. To punish Adam and Eve (incredibly harshly) for doing something which by definition they couldn't know was wrong seemed impossible to justify, like holding a pre-verbal child to the standards of an adult.
(I hope I've made my objection clear; I have rarely if ever gotten a religious Christian to understand it, or at least to admit they understood it.)
Now, the Catholic Church does not in modern times insist on taking the Bible completely literally, which does save them from having to explain some of the more obvious impossibilities. (Then they dispose of the advantage by declaring the Pope infallible ex cathedra but that's yet another story.) Acceptance of (suitably theistic) evolution was allowed even thirty years ago, and the Eden story could be regarded as a parable, an allegory, a story essentially but not literally true. (Unlike, say, virgins getting pregnant or three-day corpses returning to life, but that's yet another whole collection of stories.)
So, since it was just a story, I decided to rewrite it. My version, somewhat condensed, went something like this:
There were in Eden two Trees, a Tree of Life and a Tree of Knowledge. God, who was knowing*, did not want Adam to become as God was, and therefore warned Adam that if he ate of the latter he would surely know death.
Now it happened that the serpent, who was one of God's earliest creations, found himself becoming too slow to obtain his customary food. The serpent therefore ate instead the fruit of the Tree of Life, and that night to his astonishment he shed his skin and became young again.
Eve saw the serpent and, amazed at the transformation, asked the serpent how he had become so beautiful. The serpent duly told her that he had eaten the fruit of the Tree, and had shed his skin during the night, and been made clean and new by it. Eve decided therefore to eat from the Tree also, thinking to make herself beautiful for the pleasure of Adam's sight.
Unfortunately, she plucked the fruit of the wrong Tree; she ate from the Tree of Knowledge, and not the Tree of life.
Adam came upon Eve just as she ate, and he was horrified at the thought that his heart's love would die, simply because he'd failed to pass God's warning on to her. When Eve explained to Adam that the serpent had already eaten of it, that it would not kill them, and that in the morning they will have beautiful new skins, Adam wanted so mightily to believe her that he began to doubt his memory of God's warning.
In any case he did not want to live without Eve, if she were to die, so Adam bit into the fruit also.
Alas, when the sun rose their skin was not made new as the serpent's had been, and for the first time it appeared ugly to them, for they saw how it had the beginnings of age upon it. Ashamed for the first time of their nakedness, they set about making new skins for themselves out of leaves and thread. Thus it was that when God came looking for them, they were hidden in the forest by their clothes. Their shame had hidden them from God's sight, and when God realized this His Heart filled with angry grief.
God then proceeded to tell them that they would now know death, and age, and sorrow, and pain. God was not imposing punishment on them by this; rather, those things had already existed in their lives, but they didn't know those things. They were unconscious of the meaning of death, in their innocence, but now they knew death, just as God had originally warned Adam he would.
By eating of the Tree of Knowledge, they had indeed become like God; they had become adult, in fact, and not even God could ever return to them the Eden of their former innocence.
* Not, you'll note, all-knowing, any more than he was in the original.
I was rather pleased with my effort. Not only did it avoid holding the first people culpable of evil despite their innocence from evil, and not only did God come off less of a vindictive bastard, but even the serpent caught a break from the blame-fest... yet it still retained and even expanded upon the themes of natural justice, of the loss of innocence and the shouldering of responsibility, plus it put in a good deal more about the nature of love.
Did I mention the school practiced corporal punishment? My ass was bruised for a week.
The physical beating was nothing compared to the guilt trip they put on me, though. Rewriting a bible story? I learned it was the blackest sort of heresy, and my soul was a hair's breadth from being used as Lucifer's cigar lighter. Oh, I can joke about it now, but I believed then, and the idea terrified me to tears, even more than the idea of them calling my parents in. I avoided both fates by agreeing to hie me to the church to confess and repent directly after school, which I did. And yet, and yet...
It did not escape me that I was suffering dire punishment, and threats of more punishment, infinitely worse punishment, for doing something I hadn't even known was wrong, and with the best of intentions. More, in the course of haranguing me and batting aside my explanations, my teachers had made clear to me that hellfire awaited many, many innocents - millions of them, in fact, millions guilty only of not knowing what God considered a crime, not knowing what God wanted.
It also didn't escape me, upon reflection, that God could have avoided all that, by being just the teensiest bit clearer in his wishes and evident in his presence... and therefore he must have wanted it to be that way.
As I said in the beginning, it took decades more to get where I am; one decade to fully shake the belief, I'd say, one to shake the belief in belief, and this last one to fully commit myself, publicly and proudly, to fighting the evil skewing that religion does to the minds of even - dare I say it? - the innocent.