@Johnny Fresh,
A couple of remarks on the 'God concept'.
In having a discussion about these topics, we will form some understanding of the idea of God and feel that we know what is being referred to.
However I will suggest that whatever the concept is, it is really just a placeholder. It is a placeholder in the conversation which occupies the space that the ostensible notion of God resides in.
Because although it is true that you can have more or less accurate conceptual and verbal depictions of Deity, the 'thing in itself' is beyond the conceptual mind.
This is why 'religious experiences' or 'conversion experiences' are so fundamentally re-orienting. Those who undergo them frequently report that there entire understanding, not only of what 'God' is, but the nature of life itself, are completely re-arranged by a moment of 'experience of the sacred'.
Now I am not trying to browbeat anyone with this idea, nor claiming that I have had such an experience and therefore know something special. The point of saying it is to highlight that there are non-conceptual spiritual experiences, which people do have, and have been reported from across all cultures, peoples and times in history. If you study what these reports say, or have such an experience, it often will put the question in a different light. And a conspicuous and oft-repeated statement in all of these experiences was: "All my ideas about God were wrong".
Still, I know this is a philosophy forum, and it is perfectly sound to discuss these ideas anyway. But it is important to bear that caveat in mind.
As to the question: 'How does one know whether God exists' - an answer from my personal perspective.
First, God is beyond existence. This is not evasive or sophist. But God is not a material phenomonon or thing of any kind. So you can argue whether God exists or not, but 'is God real'? is actually a different question to 'whether God exists'. If God is the underlying reality beyond all existence, then the notion that God merely 'exists' is red herring. It is a different order or level of reality or being altogether.
So you could ask, 'Is God real
for you?' And I would say that if one answers in the affirmative, then one has faith in the reality of God. Faith is different to knowledge. I know what time the bus comes in the morning, how to type, how to poach an egg, the chemical composition and many other things. But this 'sense of abiding presence' is of a different order to knowledge of that kind.
Here is an interesting quote from a well-known scientist, Albert Einstein:
Quote:I'm not an atheist. The problem involved is too vast for our limited minds. We are in the position of a little child entering a huge library filled with books in many languages. The child knows someone must have written those books. It does not know how. It does not understand the languages in which they are written. The child dimly suspects a mysterious order in the arrangement of the books but doesn't know what it is. That, it seems to me, is the attitude of even the most intelligent human being toward God. We see the Universe marvelously arranged and obeying certain laws but only dimly understand those laws.'
Albert Einstien: His Life and Universe Walter Isaacson, Unwin Books, 2006, p386.