Wesrock:
I’m very much aware of what special pleading is. Your statement here again confirms you didn’t follow what I was saying and don’t understand what is meant by monotheists when they speak of God and you don’t understand the arguments for His existence (whether you agree with those arguments or not).
Can the argument for God’s existence be used as an argument for
anything else besides God? Ideally something that could
also be demonstrated to exist using more conventional means?
You don’t follow. It’s not a matter of proposing a hypothetical being without any supporting evidence and just claiming “this is different.” It’s like feeling heat and proposing that there must be a source of heat, then using reason based on what you know to determine what the source of heat cannot be to learn more about what it is. Or seeing a balloon rise and proposing that there must be some principle by which it rises, and using reason to rule out what cannot be reasons the balloon is rising to narrow down to what that principle is. It’s a rational inquiry backwards from what is known and experienced, not starting with the claim of a unicorn and searching forward for knowledge and experience to support it. We experience the effects and look for a reason/cause. We aren’t starting with the idea of a cause (unicorn) and then looking for its effects (unicorn hoofprints, unicorns reflecting light so they can be seen, etc…)
Things exist. Things change. Things are composite. These are observations about reality. Likewise with observing heat and concluding there must be a source of heat, or seeing a balloon rise and concluding there must be a soure or principle to that, there are arguments to be made from these observations that there must be a principle, a reason, for such things to be happening. A first cause or prime mover, if you will. And in doing so you must rule out all things that cannot be a first cause by identifying all properties and attributes that require causes or reasons external to themselves, such as extension through space, changing, being composite, coming into existence, etc… From there it can follow that, based on everything so far, if it necessarily follows that this principle “have” something analgously similar to intelligence and will. The line of argument concludes that there must be one (and only one), eternal, omnipotent, omniscient reality that is the principle (foundation, source, origin) of all other reality, in a sense more real than the reality we experience (analogous to how a dog sitting beside you is more real than the dog you imagine in your head).
Note: I have not given an argument from change, or an argument from contingency, or an argument from composite things, or anything along those lines. I haven’t elaborated on why something that is changing or composite or contingent cannot be the first principle. The information is out there and it’s a lot to go through.