The theory of God exists, but that does not give us certainty beyond speculation, regardless of the effect of the speculation on individuals.

To respond to an experiential testimony to the experience of the divine is not well thought out and churlish - I try to refrain from using such harsh language in a philosophical setting, but to undermine the veracity of someone's claim such as that is highly uncharitable; though the specific name of the scientific journal is escaping me right now, there was a study done (then subsequently covered in the New York Times) showing that Evangelical Christians, when (what is known as) speaking in tongues, utilized a part of the brain which is otherwise inoperative - they [the Christians] call the feeling of taking part in such an act as a religious experience. This is not unlike the Calvinist idea of Sensus Divinitatus, whereby he [Calvin] posited that humans have an engrained psychological faculty whereby they are able to "experience" God. So please - do not dismiss an experience such as this as a mere hallucination or the ramblings of some madman when there are a number of fascinating arguments for the truth value of these claims.

I think there's less of the mental-dependency/independency factor and more of the kind of influence at play. A stone by itself cannot affect any breakable object though it has the potential to. I think the same applies to the God religion's project to us. As far as I can tell, God's influence is specifically tailored to affect our mental circumstances the same as a narrative. However, if we are not acquainted with God through any narrative, I suspect there would be little influence, if any.
I think it's the same for the stone, once its physicality is projected towards a breakable object, the inevitable effect takes place. And just as, not all breakable objects break the same, so also, not all people are influenced the same by the influence of a God narrative.

Therefore, I think that God exists. However, that existence is, as far as we can manifest it, limited to our mental circumstances and its consequent effects upon them.

I would just call gods existence a fiction of the bible, or religion. That is the way god exists. That seems like more direct phrasing to me.

Therefore, I think that God exists. However, that existence is, as far as we can manifest it, limited to our mental circumstances and its consequent effects upon them. — BrianW

Isn't that basically what I said?

I was a believer at one time. I remember the feeling I got when thinking about the power of God. It was no different than thinking about a beautiful sunset, or thinking about the enormity and power of the universe. Have there been any studies about what part of the brain is used when thinking about those things as opposed to thinking about God, or speaking in tongues?

If you want to believe the claims of the religious, then which religious claim do you believe? There are many, and many contradict each other. They all can't be right. What method do you use to determine the validity of any claim that another human being makes? It seems to me that you accept all claims made by other human beings simply because of how they feel when they make the claim (their emotional attachment to the claim) .

“The most beautiful thing we can experience is the mysterious. It is the source of all true art and science. He to whom this emotion is a stranger, who can no longer and stand rapt in awe, is as good as dead: his eyes are closed.”
-Albert Einstein

The Science of Awe
https://ggsc.berkeley.edu/images/uploads/GGSC-JTF_White_Paper-Awe_FINAL.pdf

Unequivocal evidence for or against the existence of God are, on the whole, not compelling in my opinion - rather I believe the burden of proof to be on the non-Theist to affirm non-Theism, as opposed to giving into the proclivities of weighing facts of natural science against ecclesiastical traditions. — alsterling

Would you care to translate this into English? And if it's an argument, what it's to and how it works?

I don't necessarily disagree with you, but I do think your argument is weak. It is your assumption that human behavior is due to "God". However, scientifically speaking, without first proving the existence of God, you can't assert that the effects you experience are due to God.

Also, God as a concept is not like a stone. God is like every stone, the idea of stone, and every idea ever, and everything in existence ever. It would be probably more defendable to say God is existence itself, and everything in existence is an expression of God. This is a similar assumption to science's universe, basiqually equating God to it, just with a different expression. This way God does not conflict science, nor does science conflict with God.