Generally speaking, a term defining reality's supreme manifestation of itself, the word "God" in the English language has its roots in ancient Norse gutteral linguistics, and means literally "loud noise in the sky".
Most modern Western religions can trace their roots back to Judaism, a theistic system practiced by early Semites living near the region of Mesopotamia known as 'the fertile crescent'. Abraham, the founder of Judaism (an important figure still in the histories of all three major Western religions) came from the city of Ur, a Sumerian trade centre. The Sumerians of that time were polytheists, and it is likely that Abraham was nominally one as well. Judaism was not originally monotheistic in character, but it did ascribe prevalence to an "overall god" who was more powerful than the others.
Early Judaism was profoundly mystical in character. In Judaic mythology, a tale can be found wherein God is quoted as identifying Himself by the title JHVH, which means 'I am that I am'. Although pronunciation of the term was forbidden for most of its history, it could theoretically have been pronounced 'Yahweh'. The myth has it that Yahweh made this revelation of Himself from a burning bush, possibly a marijuana plant given the rather prevalent role played by various psychoactive substances in most mystical/religious contexts.
Still, the idea that divinity is exemplified by conscious self-awareness is reminiscent of some of the theories coming out of 20th century physics, wherein the universe is seen to be a set of relationships whose parameters are defined by a 'bootstrap' comparison of things one to another with conscious observation providing the context.
Eventually, the mystical aspects of Judaism lost much of their cohesion when the Deuteronimists (a theocratic political regime, basically) rightly or wrongly decided to revise religious practice by informing their subjects that they were going to be damned by this Yahweh if they ate shellfish or didn't cut off part of their penis. Apparently, the threat of anaphalactic shock, or of having one's penis constantly irritated by sand under the foreskin, was not quite enough of an incentive in and of itself to ensure adherence to basic standards of hygiene. The Deuteronimists worshipped Yahweh as a war diety, and honoured His intercession on their behalf in battle by ritually sacrificing livestock to him. At least, they did until the day that Yahweh for some reason decided not to intercede on their behalf, the result being that their nation was sacked by the neighbouring Chaldeans under Nebuchadnezzar, who deported the wealthy elite of Judah (numbering around 10,000 or so) back to the city of Babylon.
><> THUS SPAKE ZARATHUSTRA
Zoroastrianism, founded by Zarathustra (Zoroaster in Greek) sometime around the 6th century BCE, succeeded rather well in supplanting various local tribal cosmologies by drawing on elements of all of them to create a ditheistic view of the universe as a stage of battle between two opposing Gods of roughly equal power. Zoroastrianism clearly defined for the first time the concepts of "good" and "evil" where previously people had to make do with concepts like "shortcoming" and "contention". It also introduced the idea of eschatology to the middle east. The universe was going to wind down in a cataclysmic confrontation between the forces of Good and Evil, and Good was going to triumph.
Cyrus the great, a Babylonian ruler of that era, possibly the mightiest conquerer human history has ever seen, was an ernest disciple of Zoroaster. In his mind, the final battle was fast approaching, and he intended to be on the field with his armies in the service of good. To that end, he identified nations whose gods he felt were evil, and set about annihilating them.
Nations whom Cyrus felt worshipped good gods were free to continue to do so. In his view (probably the prevalent view of the age) many gods existed, and all "good" gods served the demiurge, overgod, or whatever you want to call it. Legend has it that Yahweh came to Cyrus in a dream and told him to restore the practice of Yahweh worship in the land of Judah. To that end, he sent the Jews still living in exile in Babylon back to Judah for the express purpose of re-establishing the worship of their god. He also kindly rebuilt the temple in Judah, which had been destroyed during the Chaldean conquest a century earlier.
Judaic culture thus re-emerged as an even more profoundly theocratic institution than it ever had been, because it was rebuilt for the express purpose of Yahweh worship. The neo-worship of the jewish god was at best severe and draconian in character, and it wasn't uncommon for people to be killed by having large rocks thrown at them simply because they happened to utter the forbidden name of JHVH. Some new ideas had been introduced into Judaism during the period of captivity, however. It is likely that the Torah took on its final shape during this time. The creation myth in Genesis that begins with "In the beginning..." is Babylonian in origin. Possibly the legends of the Tower of Babel and the Great Flood (which both have analogues in Mesopotamian mythology) also were picked up at this point. The tenets of Zoroastrianism also carried over, and while they probably remained for the most part heresies common to the lower castes of Israel, they would resurface with a vengeance 500 years later with the arrival of a fellow named Yeshuah or Yessue Ben Miriam.
><> YESSUE BEN MIRIAM
According to a Jewish fellow named Yessue Ben Miriam, possibly a member of the Judaic priesthood, the Kingdom of Heaven is within you. In other words, finding God has nothing to do with going to church. He also said some stuff about being nice to people. This was bound to upset someone, as at the time getting people to go to church and follow laws was pretty much the foundation of the fabric of his society, and being nice to people meant letting them off the hook when they were caught stealing food and so forth. Yessue apparently was fond of referring to himself by the title "The Son of Man" (Yessue Ben Adam) and less frequently as "The Son of God". Anyone else interested in participating in the Kingdom of Heaven could also be a Son of God.
Christianity thus began as an attempt to shake the influence of the legalists on orthodox Judaic religion, and bring the worship of Yahweh back to its mystical roots. Suffice to say it was a far cry from the kind of theology people were used to, as until then the prevalent religious archtypes commonly seen in most societies had tended for centuries to center around rituals such as the hurling of nubile young virgins into flaming pits, the drinking of blood, and the practice of cannibalism. He was thus promptly tortured, stabbed, and nailed to a stick.
Before too long, the revolutionary message that God lives in people and not in a temple found its way into the hands of a fellow named Paul, a theologian with a slightly different take on the Christian ideals. Paul set out to promote the message as he understood it, and apparently, the message as he understood it was that Yessue Ben Miriam was an Avatar of Yahweh, and that He was going to battle Satan in Zarathustra's apocalypse, and that women were unclean whores fit only to be beaten into subservience by their husbands.
Paul's teachings had a lot of influence on the formalisation (or formulisation) of the Christian faith, a ball that really got rolling with the establishment of the Roman Catholic Church around 400 AD or so. Since this time, His worshippers have gone to church regularly, have killed and tortured heretics (literally, free-thinkers) and infidels, have believed fervantly that His mother was a virgin, and have practiced rituals where they ceremonially cannibalize Him and drink His blood, for fear of being thrown into a flaming pit.
><> OH LORD, OOO YOU ARE SO BIG
To this day, Judaism itself and its family of offshoot religions tend to reflect a rigidly observed Deuterocanonical outlook on life, the universe, and everything. A good deal of modern orthodox thinking tends to take shape from the practice of taking ancient writings more or less at face value as cosmological relelations rather than as applicable mythology.
In most modern Western orthodox theism, then, reality's supreme manifestation of itself is generally recognized to take the form of a patriarchal hominid characterized by a vile temper, a jealous disposition, and a capricious preference for wrathfully smiting those who displease Him. Modern Western religions hold that God created the universe, created awful people to populate it, immediately got mad at them, inflicted suffering on them to punish them for their awfulness, and hereafter has plans to extend their punishment to eternity unless they sacrifice various animals, or each other, to sate His continual thirst for blood. Many Western theists recognize the brutality of this view, and try to soften it for consumption by comparing it to a fatherly, stern, compassionate brand of love. Fatherly, stern, compassionate love is characterized in the book of Deuteronomy by the command to 'stone disobedient children' (Deut 21:18-21)
It has been noted that humans, being descended from monkeys, are rather fond of giving primacy to ideas representative of a pack alpha-male archtype.
There is still room for a good deal of variation on this view of nature, as seen in the various schools of Judaism, Islam, Catholicism, Protestantism, and so forth. Orthodox (right-believing) members of these various faiths bicker amongst themselves about who has all the details right, but tend mainly to agree that religious life involves proving one's devotion to an institutionalized concept of divinity in order to avoid the afterlife of eternal torment due to them as punishment for their shortcomings (the term 'sin' meaning, literally, 'falling short of the mark'.)
Practitioners of these faiths (there's a lot of them) often tend to go around expressing pretty strong feelings about Yahweh, Allah, or the person of Yessue Ben Miriam, and to be fair, many of them seem to be quite well-intentioned. Christianity, for example, is for many the religious practice and experience of love.
It is, perhaps, sad to note that the Prince of Peace that is worshipped to this end happened to be the figurehead on the banner of the Crusades, the Spanish Inquisition, Vlad the Impaler, the Conquistadors, the British Colonialists, the Nazis, and the Americans, and as such, has been invoked as a reason to kill far more people than has, say, Satan. Noone can say for sure what Yessue Ben Miriam might have thought about such a thing, but it is a safe bet that Cyrus the Great would have approved.
Michael Palin, the great comedic philosopher, once summed this all up rather succinctly when he dressed up as an Anglican priest and prayed, "Oh Lord, ooo you are so big, so absolutely huge. Gosh, we're all really impressed down here, I can assure you..." He Then leads his congregation in song:
"Oh Lord please don't burn us
Don't kill or toast your flock
Don't put us on the barbeque
Or simmer us in stock"
Beyond the orthodox traditions of institutional thinking, many philosophers have grappled with the Western view of nature, sometimes by harkening back to the mystical roots from which it is derived. The works of St. Anselm describe God as 'that than which nothing greater can be conceived of.' This definition originated as the basis for Anselm's ontological argument for God's existence. It really puts the onus on God to be pretty spectacular.
Metaphysicists concerning themselves with theological issues might accept that the Western model has some relevance and meaning in its proper context. For instance, it might be pointed out that it is sometimes useful to think of God as being a hominid, since humans are the only known religious animal that even bothers with trying to relate to it. In other words, humans are part of reality, so Ultimate Reality is therefore demonstrably partly human.
One philosopher by the name of Nietzche pointed out that any being with the grandeur and power to create all of this reality at a whim would do so only because He/She/It sought the companionship of co-creators, rather than the abasement and grovelling of cosmic slime. Nietzche is generally more famous for observing that God is probably dead. God gets quoted quite a lot as observing that Nietzche is dead.
><> AN IMMENSE UNIVERSE FULL OF STUFF
Eastern theologians hold that God is in fact one with creation, the 'ground of being' if you will. This is a generalization, but more or less accurate, particularly in the case of Taoism. In the scholarly Eastern traditions, all things that exist are considered to be fragmentary pluriform aspects of God. The purpose of God, or Brahmin or the Tao if you prefer, is to observe every possible aspect of Itself that It might know Itself better, and It seems to go about this by manifesting as an immense universe full of stuff capable of doing so.
That being the case, many religious practices in the East nevertheless tend towards obeisence to pantheons of mystical entities. These variant tenets are not as contradictory as they first sound, as each god of the pantheon in question can be seen to be a face of the Ultimate... scholars in Eastern traditions tend to recognize that their pantheons are representative symbols that embody universal forces or aspects of human struggle.
These sorts of notions don't always catch on with the general populace, many of whom often tend to take their pantheism a bit more literally. Again, there are several variations and schools of thought in this vein, and a good deal of overlap, but the main players seem to be Buddhism, Taoism, and Hinduism.
The wide variety of ways in which devotees of Eastern faiths have been found to express their worship for these entities is a testament to the fertility, depth, and profound weirdness of the human imagination. It has been noted that Eastern religions tend to be far more open and all-embracing than Western ones, at least in theory.
There are elements of Taoism in particular that at first glance seem roughly analagous to the binary ditheism originating with Zoroastrianism, which leads one to wonder whether Zarathustra got to spending some time out east. Taoists have the yin and the yang, which roughly speaking represent male and female, hot and cold, up and down, light and dark, chaos and order, and a host of other paired opposites. In Taoist thinking, all form springs from interaction between these two forces. This, again, isn't too far off of modern metaphysical thinking, which supposes that all form is given meaning and context by relative interaction with an observer-participant.
><> HAIL ERIS, GODDESS OF DISCORD
Discordians think that God is a crazy woman named Eris. Discordianism offers useful tactics for arguing theology, and their practice of such an art generally involves the obnoxious utterance of barnyard noises.
There is some evidence that prior to the dawn of recorded history, before the Mesopotamians farmed the fertile crescent, that widespread worship of a female goddess was the norm throughout most of Eurasia for milennia. People of that era seem to have worshipped eggs and statues of a pregnant woman. Anyone who has ever lived with a pregnant woman will see an immediate correlation to the view of God espoused by the Discordians.
><> AZATHOTH THE BLIND PIPER
According to fiction written by H.P. Lovecraft, God is an amorphous, mindless blob at the center of the universe, flailing about with various tentacles and appendages and thus creating the random stirrings from which all things spring.
This would explain quite a bit, and is somewhat reminiscent of the Hindu diety Shiva (considered to be the prime incarnation (or symbol) of the Brahmin), whose cosmic dance of creation and destruction is the essence of all things material.
The Gnostic heresy describes the material realm as the creation of a deranged sadistic demon called the Demiurge. The gnostics figured that life was a prison in which their souls were serving a sentence. Very little is known about gnosticism thanks to the Catholic church, who wiped the creed from the face of the earth at the first opportunity because of the threat it posed to orthodox Christian ideology.
The notion that God is insane, random, blind, drunk, and/or has a malicious but inventive sense of humour is rather common amongst the disaffected.
Ancient Sumerian cuneiform tablets containing the epic poem "The Enuma Elish" go on at some length about Tiamat, the dragon goddess of chaos. One tale concerning Tiamat (probably from the early Babylonian era, after the Akkadians had introduced some new gods into the Sumerian pantheon and adopted it for themselves) holds that mortal life was created from the blood shed by Her when Marduk slew Her in battle and rent Her body in twain. This sort of death-and-rebirth thing, where God sheds His/Her Godhood (or dies) to become multiple finite pluriform mortal versions of Him/Herself, is pretty common to many ancient religions, as is the motif of order springing from chaos. Even the creation myth in Genesis (borrowed by the Jews from the Babylonians, kissing cousins of the Sumerians, during the Jews' captivity there) uses similar imagery, describing a spirit of reason and principle joining with a sea of chaos to create everything, yin and yang.
An interesting correlation here is the study of chaos theory, of non-dynamic systems on the verge of becoming dynamic exhibiting looped mathematical patterns (such as Hostaedter might have called 'strange loops') when an external flow of energy is present to abet the process. Chaos theory is related closely to the study of the fractal geometry of nature, which describes the tendency of realities to contain infinite variant subsets of themselves.
Considering that there is ancient Hindu poetry dating back several millenia describing fractals, and Zen koans going back at least as far describing a puzzle very similar to the problem of quantum uncertainty, one may find oneself wondering whether some of those ancient mythmakers pretty much knew what they were on about.
><> THOU ART GOD
According to Robert A Heinlein's book, Stranger in a Strange Land, Thou art God. It is a rather empowering concept, even if it does carry a lot of attendant responsability.
><> A TOY CALLED GOD
According to Tolstoy, it is a terrible thing to see a man who has the incomprehensible in his grasp, does not know what to do with it, and sits playing with a toy called God.