Here's what led me to begin thinking about this.
I attended a Catholic high school. For seniors, a priest gave a course called "Apologetics" - meant to show that it's possible to prove, through logic, that Catholicism is the one true faith.
The methodology consists of having a person try to start with no preconceptions, and question whether there are reasons to believe in the necessary existence of a Supreme Being, the Creator of everything else. When the person has become convinced of that (the priest was sure we would be), he or she should then consider which of the world's major religions is the true one. And having (of course) concluded that Christianity is the only possible choice, consider the arguments for various denominations, and conclude that Catholicism is the true form of Christianity.
Unfortunately, I only remember one of the priest's many arguments. But I later realized the one I remember is based on faulty reasoning. Here (in my own words) is the argument: "Some Protestants say Jesus was an enlightened spiritual teacher, but wasn't divine. That can't be - because he claimed to be divine! So if he wasn't, he couldn't have been an 'enlightened spiritual teacher.' He would necessarily have been either deranged, or an out-and-out fraud." The intent, of course, is that everyone should agree that he was divine.
I now know that's a standard Catholic argument. There's a name for it: "Liar, Lunatic, or Lord."
What's wrong with it? We have no way of knowing what Jesus claimed! All we have to go on are the writings of early Christians who never knew him, never heard him speak. There are no objective (or in fact, even very early) sources. The earliest surviving account of his life, the "Gospel According to Mark," was written by a Greek-speaking believer, outside Palestine, some forty years after Jesus's death. And the Gospels are especially suspect on the issue of his claimed "divinity," because the most exalted claims appear only in the last-written canonical Gospel, the "Gospel According to John."
Critical scholars reject the notion that any of the Gospels were written by Jesus's disciples, despite two of them having been given the names "According to Matthew" and "According to John." All four were written and first circulated anonymously. And there's general agreement that despite their traditional order in the New Testament, "Mark" was written first, and was one of "Matthew's" and "Luke's" sources.
If my young self had recognized that blunder on the priest's part, it probably would have caused me to doubt everything else.
At age sixteen, I did accept everything he said. But by the time I reached my mid-twenties, I had serious doubts about Christianity.
I decided to use the methodology that priest had suggested. Started from the beginning, and asked whether the existence of the Cosmos is necessarily dependent on the prior existence of an Uncaused Cause - namely, "God."
As an adult, my answer was No.
So I had no need to go further, and weigh the merits of different religions. (But I have learned a good deal about Christianity, and see no reason for embracing it.)
Re the origin of the Cosmos, one might say there are two "outlier" possibilities, which can be put aside, to one side and the other:
1. A literally infinite chain of Causes and Effects. This is no more implausible than the notion of some single Being's having existed "forever," which is what most monotheists believe of "God."
2. The existence of levels of reality on which "Cause" and "Effect," as understood by humans, don't apply.
If either of those possibilities is the truth, there's no point in trying to pursue them further.
The remaining main possibility is that everything began with an Uncaused Cause. But since we can't exclude the possibility of one of the outliers being the truth, no "explanation" can be more than a hypothesis.
The Uncaused Cause could have been any of a number of things.
The alternatives include the possibility that some completely lifeless "thing" somehow set an evolutionary process in motion. Or that a rudimentary form of life appeared and did that. Or that - even though the chain of Causes and Effects isn't infinite - our Cosmos isn't the first, and its origin can't be understood without knowledge of what preceded it. There are doubtless many other possibilities.
But what if the Uncaused Cause really was a separate, thinking Being?
If it was, that Being...
May or may not have existed and had its supposed powers "eternally."
May or may not still exist.
May or may not be (or have been) omnipotent.
May or may not be (or have been) omniscient.
May or may not have created the Cosmos intentionally. (And if the creation was intentional, we don't have a clue to the motive.)
May or may not have taken a continued interest in its creation.
May or may not have changed (for better or worse), in its nature or intent, since it created the Cosmos.
Claimed "revelations" can't be accepted as proof of anything. Least of all, claims made by unknown authors, thousands of years ago, about "revelations" supposedly made thousands of years before their time, riddled with contradictions and flat-out impossibilities.
And if we imagine a preexisting intelligent Being as the Uncaused Cause, we have to ask how it acquired its intelligence. The intelligence either "developed," somehow, or was "always" one of its characteristics.
In a reality in which we're trusting our perception of Cause and Effect to be real and meaningful, we should also have enough trust in our perception to recognize that order and structure exist in the Cosmos. ("Order and structure" - not necessarily "intelligent design," which implies a preexisting "designer.") Life, and intelligence, undoubtedly exist within it; and it may, in a sense, be growing. Everything we know exists was once contained within the singularity that produced our "Big Bang."
So it's possible that the Cosmos is a gigantic Being.
And whether or not we think of it as a "Being," the Cosmos itself may be the Uncaused Cause.
How might it have come into existence? Some scientists now speculate that "Big Bangs" create new universes (within the same Cosmos) from the eruptions of supermassive black holes. (That provides a response to the argument that since the "Big Bang" could have produced many results, its having given us a viable universe proves "intelligent design." If many "Big Bangs" are taking place at any given moment, somewhere in a vast Cosmos, some will inevitably result in viable universes.)
But years ago, when scientists first realized our universe was not going to end in a "Big Crunch" that might be followed by another "Big Bang," they thought everything was going to fly apart - even individual atoms - and simply end. Isaac Asimov, however, wrote that there was hope...because there are always random fluctuations in a vacuum, and one of those fluctuations might give birth to another universe. I know Asimov wasn't a scientist, but he was a brilliant man.
Was a "fluctuation in a vacuum" the infant Cosmos? (And if so, is even a vacuum a "thing," whose origin has to be accounted for?)
Personally, I choose to accept as a working hypothesis, a guide to live by, that a Cosmos that came into existence as a "fluctuation in a vacuum" - and has been evolving ever since, with life and intelligence developing as features of that evolution - was the Uncaused Cause.
Consider two possibilities for that Cause: the Cosmos itself, vs. a completely unexplained separate Being that somehow had the power - and desire - to "create" such a thing. And chose to create a Cosmos in which eons would have to pass before intelligent life could appear. If we think of the Cosmos as the Cause - especially if we think of it as a living Being - at least a rudimentary form of Mind was probably there from the beginning. But if we assume a separate "Creator," there's no reason to think any form of intelligence existed within the Cosmos until it could evolve in animals, on planets.
If we trust "Occam's Razor," the simpler possibility - the one that requires fewer assumptions - is the more likely to be correct.
I read recently that some astronomers are accepting the possibility of what they're calling "panpsychism." Basically, it's the idea that some type of consciousness permeates our universe. I've even seen speculation that individual stars are conscious, and follow their orbits deliberately.
I'm not ready to believe in conscious stars. But I can believe that there are a vast number of cells in my body. Many different kinds of cells, not conscious in themselves (as far as I know!), but parts of a larger, hopefully intelligent being.
And there may be an analogy: I myself may be one of a vast number of cells, of different kinds, in the body of the Cosmos.