What is Catholic?

A complicated story, really, though hardly uncommon. You're right to start here, of course, given the importance of the emotional meanings layered in it for the reasoning that follows. But perhaps, precisely because you do need to start with a story, you should then proceed directly to articulating the actual subject of the essay, informing the reader clearly about what's to follow, leaving the story to resonate, as in vibrato, around the actual note being struck.

Because of course the Church, founded long before this nation and on very different principles, doesn't actually need or want to conform its practices, doctrines, and its bigotries, let alone its basic sources of political authority, to those of the upstart republic within which it momentarily is compelled to exist.

It seems to me that it matters, to this story, whether the speaker was saying that she wouldn't have an abortion herself, "because I'm Catholic," or whether she was saying instead that she supported making that decision not only for herself but for all other women, on the same ground. In the first case, she's saying that she was brought up in a particular moral and cultural system, and she therefore believes that voluntarily ending a pregnancy is wrong, so she wouldn't do it. In the second case, she is stating that she's committed to the belief that her religion and moral system are exclusively right, all others are wrong, and it's her duty to impede or prevent the ability of other moral systems to function in the community where she lives, so far as is consistent with the discipline and current policy of the Church, as expressed through the (exclusively male, "celibate") hierarchy. The two meanings of "because I'm Catholic" are obviously quite different. She might mean either. Her bishop, on the other hand, and even her parish priest, are required to mean the latter.

You are saying that, for you, the latter meaning is personally inaccessible, and perhaps repugnant. As you say, that would make you, from the Church's point of view, not Catholic in your doctrine. Depending on the degree of insistence on orthodoxy, convenient to the Church at the moment, refusal to conform would be either peacefully ignored, as in the United States at present, or violently suppressed, as in Spain until the 19th century, or somewhere in between.

Whether the test of a creed's social utility should be its effectiveness in arranging the thoughts of a powerfully intelligent and clear-minded seven year old is hard to say. On the one hand, no system incapable of answering such a child's questions is worth serious consideration, which is why—as Gibbon famously pointed out—none of the great Greco-Roman thinkers who lived at the time of Christianity's founding gave the slightest sign of interest in the intellectually negligible philosophic content of the new religion. Despite the immensity of powerful thought subsequently generated in the Christian world, and even under the particular direction of the Roman Catholic Church, the philosophic basics of the religion are incapable of resisting the straightforward realism of a bright and inquisitive child, possessed of a rudimentary understanding of the scale and nature of the universe, and set upon having important beliefs confirmed by immediate tangible demonstration. We are scientists from the crib. "Faith," like other forms of dubious cognitive sophistication, we must be taught by someone less realistic than ourselves.

On the other hand, the Church, like any other cultural system, can only exist by addressing unconscious aspects of human life with which the child mind is not yet in a position, experientially or developmentally, to cope. Purgatory, as Luther perceived, had its origin in an immense scheme of taxation, to take the dead hostage in order to extort property from the living. Yet so adroitly does the concept answer to the unconscious needs of our psyches that even as penetrating a skeptic as Erasmus was unable to stop believing in it.

This section is weak. It veers from spot to spot under poor argumentative control. That priests are sometimes criminals, or that voters vote sometimes vote against their economic interests are not particularly relevant points for you in the context you've set so far.

Your argument so far is that the form of social discipline on which the Roman Catholic Church is based does not naturally lend itself to coexistence with democratic polities based on freedom of thought. This is historically correct. Your references to Arnold bring more baggage with them, perhaps, than they are worth, and too rigid a functionalism about religious institutions loses some important portions of their social meaning. But the centerpiece of your inquiry, beginning with your own story of childhood heresy, is to interpret the consequences of remaining at least partly within a cultural system in whose shaping myths one no longer believes. Arnold himself, if you mean to maintain his relevance, would say that this is inevitable for any observant and self-aware person in any organization, because creeds are inherently self-contradictory and vacuous, as they must be flexible enough to carry the organization coherently across social changes that compel modification of operating principles. But he means "creed" differently than we mean it when we talk about the Nicene Creed.

Belief

But this is nonetheless an insight well worth your further consideration. The private religion of many congregants is no doubt the same meditative discipline you are discovering in yourself. You have been discreet enough in this essay not to express directly the state of your theology, Christology, conception of the Eucharist, etc. But whether you believe or do not believe that the body and blood of the risen Christ are actually present in the miracle of the Mass has ceased to matter. The value of the experience has shifted to the well-learned and well-beloved habit of the dismissal of distraction, the subduing of hectic consciousness. That value you can make for yourself, as the most spiritual of Protestant seekers also discovered. Or, at the price of outward conformity to myths no longer inwardly engaged, you can remain within the bosom of the Church, and take your meditation in that familiar weekly form.

I don’t fit into the prototype created by the creed and written constitution of the Church. But then again, Robinson, despite not fitting the mold of the criminal lawyer nor believing in the legal system of “equal justice for all,” was still a part of the legal system, whether he “believed” in it or not.

And is in that respect like every other individual engaged within the structure of any social organization.

This is a very valuable first draft. More than anything else, it seems to me, it requires sharpening: you need to give a clear statement early of precisely the idea you want to get across to the reader. You should explicate it in the successive paragraphs with clarity, and return thereafter to the consideration of the personal implications you find in it. Losing the personal quality of the essay would be a shame, in my view, which puts a little more pressure for concise development of the central theme.