Once upon a time, people believed that the gods walked on Earth and any suggestion that they lacked material bodies would have been greeted with uproar. More recently, it has been held that God is something like a disembodied spirit, and has attributes such as omnipotence, omniscience and omnibenevolence. Other theologians have offered other ways of understanding God which critique some of these. Process theologians nuance omnipotence, preferring a God who lures us toward right actions, while the existential theologian Paul Tillich would argue that God is not an existing being, but is Being itself. My point being, that people who are interested in such things have never agreed on a definition. No doubt they never will; and it will always be in transition as our experiences change.
It's not just theological words that do this. Consider the word atom. I am fairly sure that atoms exist. The ancient Greek philosopher Democritus supposed that one could minutely divide matter until one arrived at something that could not be further divided, an atom. Then we found even those could be divided further with components of positive and negative charge. How we imagined atoms made of positive and negative charge has changed from plum pudding to electrons orbiting a nucleus to orbitals and wavefunctions... We don't have to understand all this, but even scientific words change their meanings and embody evolving concepts.
Language is never static. I will be using a broad definition for the word "God", as I will for other words with religious connotations - including "religious". For example, when I think "idol", I do not merely imagine a thing carved and painted and worshiped. I think of how we worship our own creations; our Unitarian Universalist Principles and Purposes speak of "idolatries of the mind and spirit". Now I realize that using definitions like this will not make everyone happy. People on both sides of the religious divide ("believers" and "unbelievers") have their interests in particular definitions, rather than the broadest ones. The broad terms bring the greatest number to the conversation, and allow us to examine traditional authorities in a modern (post-modern) light.
What to me seems essential about the term God, is how beliefs and faith concerning God have served historically as an ordering principle to people's lives, whether they understood it to be corporeal or spiritual, and whatever other attributes gods have been thought to possess. In his essay "A Faith For The Free", Unitarian Universalist James Luther Adams uses this line of thought as he asserts that everyone has faith in something.
“The question concerning faith is not, ‘Shall I be a [person] of faith?’ The proper question is, rather, ‘Which faith is mine?’ or, better, ‘Which faith should be mine?’ for, whether a person craves prestige, wealth, security, or amusement, whether [they live] for country, for science, for God or for plunder, [they show] that [they have] faith, [they show] that [they put their] confidence in something.
“The faiths of the twentieth century have been as powerful and influential as any that have ever been. They have created its science and its atom bombs, its nationalisms and its internationalisms, its wars and its 'peace,' its heroisms and its despairs, its Hollywoods and its Broadways, its Wall Streets and its Main Streets, its Gestapos and its undergrounds, its democracies and its Fascisms, its socialisms and its communisms, its wealth and its poverty, its securities and its insecurities, its beliefs and its unbeliefs, its questions and its answers.
“We must not believe every ‘pious’ [person’s] religion to be what [they say] it is. [They] may go to church regularly, [they] may profess some denominational affiliation, [they] may repeat [their] creed regularly, but [they] may actually give [their] deepest loyalty to something quite different from these things and from what they represent. Find out what that is and you have found [their] religion. You will have found [their] god. It will be the thing [they get] most excited about, the thing that most deeply concerns [them]. But speak against it in the pulpit or in the Pullman car, and [they] may forget what [they call their] religion or [their] god, and rush ‘religiously’ to the defense of what really concerns [them]. The veins on [their] forehead will be distended, [their] eyes will flash, [they] will begin to raise [their] voice. What moves [them] now is more important than [their] creed or [their] atheism; it gives meaning and direction to [their] life...”
“The faiths of the twentieth century have been as powerful and influential as any that have ever been. They have created its science and its atom bombs, its nationalisms and its internationalisms, its wars and its 'peace,' its heroisms and its despairs, its Hollywoods and its Broadways, its Wall Streets and its Main Streets, its Gestapos and its undergrounds, its democracies and its Fascisms, its socialisms and its communisms, its wealth and its poverty, its securities and its insecurities, its beliefs and its unbeliefs, its questions and its answers.
“We must not believe every ‘pious’ [person’s] religion to be what [they say] it is. [They] may go to church regularly, [they] may profess some denominational affiliation, [they] may repeat [their] creed regularly, but [they] may actually give [their] deepest loyalty to something quite different from these things and from what they represent. Find out what that is and you have found [their] religion. You will have found [their] god. It will be the thing [they get] most excited about, the thing that most deeply concerns [them]. But speak against it in the pulpit or in the Pullman car, and [they] may forget what [they call their] religion or [their] god, and rush ‘religiously’ to the defense of what really concerns [them]. The veins on [their] forehead will be distended, [their] eyes will flash, [they] will begin to raise [their] voice. What moves [them] now is more important than [their] creed or [their] atheism; it gives meaning and direction to [their] life...”
This rings true for me. I particularly like the phrase "you will have found [their] god", because it suggests to me a commonality through which we all might be able to talk about gods and Gods, even people who would say they believed in no god. Many conversations begin with an assumption that God is very particularly defined, and then proceed to demolish or provide proofs of existence from there. I do not find this a useful approach. I am interested in the role of god or God in people's lives - this is my pragmatism speaking here. From that perspective, the only important attribute is that god directs the believer's life. In fact, this suggests a good working definition for god: that which directs and gives meaning to a believer's life is their god or gods. To the extent that everyone lives to some kind of purpose, it makes sense to talk about this common experience of seeking and living purposeful lives, of following god. I would have no trouble with calling this entity, one's ordering principle (or even Ordering Principle), except that it conveys nothing of the history of its potential meanings - and is nearly six-times longer!
How this god is related to God is also suggested by the Adams passage. God (upper case G) is that which we should have faith in, as opposed to what we actually have faith in, which would be god (lower case g). I would suggest that there are of necessity some gaps here. First, between what we really should follow and what we actually follow, and second, between our ideals and how we actually live. The first would be a measure of idolatry - in the sense of worshiping what we have made. The second is a measure of something, but I'm not sure what to call it, living below our ideals.
At first sight, the inevitability of idolatry and living below our ideals might seem discouraging. Usefully, though, it is a call to humility, recognizing that there is no completely right opinion, and allowing for a heuristic pursuit of theology. And although there are surely limits to acceptable degrees of idolatry and a point where our behavior becomes hypocrisy, we might want to be cautious about using such labels of others.
Addressing the question of living below our ideals, only low ideals are easy to attain. Thus, the gap between ideals and actions can reflect well on the ideals we are striving for. Striving may be the operative word here. As long as we are stretching toward the ideal, not much more can be asked of us. Adams seems more concerned with those who claim one allegiance for appearances, but actually live for less noble ends, which hypocrisy really is about - play acting. And he may also be thinking of those who sincerely profess one creed, but live another.
Those religious traditions which do use images for worship stress that the image itself is not worshiped, but the divine is worshiped beyond the image. So we might say the same about god and God - that we aim to discern God through our god. I might also temper my skepticism with the thought that even if we cannot know exactly, then maybe we can know well enough for the purposes at hand.
In summary, from a pragmatic perspective, I am thinking of God as Ordering Principle, that from which a person ought to derive purpose and direction. I am making no other claims for that entity; it may or may not be corporeal or spiritual, have particluar powers, or be encapsulated in any specific creed or tradition. My claim is based first on my experience of people - they appear to live with purpose - for good or ill, they put their trust in something; and second, on the intuition that some purposes really are better than others. For example, that living for greater love and justice is better than living for plunder or prestige.
Toward which God (Ordering Principle) do you reach? What kind of life purpose do you have faith in? What thoughts, words and deeds align with that purpose? And why (to each of these questions)? And then, what inspires you to live and be that way? These are the kinds of questions in the field of faith and theology.