One might begin by approaching this question from what is termed “perfect being theology.” When one says “God” according to this theology, God is thought to be the greatest conceivable being. There is no being that can be conceived of that is greater than God. In fact, if something greater than what we believed to be God existed, then that greater being would be God.
The greatest conceivable being must possess what we might call great-making properties, such as moral perfection, omniscience, and omnipotence. For example, a God that is not omnipotent (all-powerful), such as in its inability to control, say, nature or the natural world, cannot be referred to as the greatest conceivable. In other words, in some sense this God would be subject to the physical universe. But surely God, if he exists, is supreme over creation. Moreover, a God that is not omniscient (all-knowing) in that, for example, there are facts in the world that he does not know also cannot be the greatest conceivable being. A being that is infinite in knowledge is greater than a being that is limited in knowledge. Further, a God that exists contingently is limited in that it must owe its existence to something else and is even at the threat of going out of existence at some point in the future.
Thus, quite rightly, if some individual came up to me and said that he is God, I’d reject his or her claim on the basis that human beings are limited, finite, contingent things. Human beings are limited in knowledge, power, and moral goodness, and cannot claim to possess great-making properties, and therefore ever be God. This presupposition seems to be intuitively and necessarily true, since nothing can be greater than God, and therefore provides a sound framework through which we can understand the other gods, goddesses, and deities of other religions.
Human beings believed/thought to be deities or descended from deities -Many people of ancient history thought they were God or representatives of God. Alexander the Great seemed to have thought he was divine. But as we noted above, Alexander, by virtue of being human, was limited, finite, and contingent. He cannot be rightly called God. Human beings are born, the greatest conceivable being must exist eternally. Human beings die, the greatest conceivable cannot die. Human beings possess limited and sometimes inaccurate knowledge, the greatest conceivable possesses both infinite and accurate knowledge. So, humans historically considered to be God or divine, such as pharaohs, some Japanese, Chinese and Roman emperors, Romulus, Homer, the Buddha, and so on were nothing of the sort since none of them possessed great-making properties.
Finite gods – This is also known as “finite godism,” which is the term used to refer to gods and goddesses that are limited in some way as in, for instance, goodness, strength, or wisdom.
i. Morally bankrupt gods – Many mythological gods, especially those believed in by the Greeks, were morally evil. On one hand, many of them were capable of compassion and justice while on the other cruelty and spite. Take Ares, for example, he was the god of war which no doubt entailed slaughter, bloodshed, and carnage. Such a god or being is morally evil and given that the greatest conceivable being must be morally perfect, such a god cannot rightly be called God. The same can be said of Poseidon of whom committed moral evils such as rape, and Aphrodite who was petty and vain over her sexual attractiveness. Countless other Slavic, Viking, Egyptian, and Roman deities share similar immoral qualities.
ii. Contingent gods – One way to determine if these gods and goddesses are finite is whether or not they are contingent. It is clear that these gods owe their existence to other things. The Aztec God, Huitzilopochtli, was born, Mithras was born from a rock, Sekhmet, an Egyptian deity, owes his existence to a divine eye from which he came, Hephaestus was born (a cripple nonetheless), and Sedna, in Inuit mythology, had a birth and was later killed. These, and countless other deities, are not eternally existing, nor are they all-powerful. An eternally existent entity does not owe its existence to anything else, like a birth or some other creative agency. Moreover, an all-powerful being cannot be killed, nor is it subject to elements within creation.
iii. Omnipotently limited – Gods thought to exist or account for certain facts and workings of nature and natural laws are limited, especially the nature deities believed in African, Egyptian, Norse, Aztec, and Japanese traditions. They are often associated with ruling limited domains such harvests (Demeter, Osiris), fertile lands (Poseidon, Ash), forests (Berstuk, Oko, Dryads, Negen), mountains (Latobius, Dali), animals (Diana, Aranyani, Yum Caax), weather (Brigid, Jupiter), the sky (Horus, Anshar, Hathor), and cosmological objects (Amaterasu, Ekhi). Even the greatest gods in Greek and Roman mythology, Zeus and Jupiter, are limited. Jupiter’s domain is limited to the sky while Zeus’ control is over lightning. The Egyptian gods Horus and Amun, like many other gods, were limited in power and even susceptible to bodily harm. Thousands and thousands of deities from dozens, if not hundreds, of cultures are limited in this scope and therefore cannot satisfy the criteria for being the greatest conceivable being. The greatest conceivable being will necessarily be one that has power over all domains, including the natural and spiritual worlds, and exist as a being that could never be at risk of physical harm or death.
Theism and Mythological gods – A final point I wish to make is that we, from the privileged vantage point of modern science, do not need gods, goddesses, and deities to explain natural phenomena and natural laws operative within the universe. For example, we know that things like pregnancy, childbirth, and the growth of vegetation occur naturally, hence we don’t need the Aztec god Xochiquetzal to explain them. Likewise, there is no reason so associate things like agriculture and wine with the Celtic god Sucellus, and we know that growth in nature occurs through natural means, hence we don’t need Persephone to explain that either. The more science progresses the more these thousands of gods are seen to be irrelevant.
However, irrespective of my personal belief in theism (“God), it is clear that mythological deities differ to a theistic concept of God traditionally believed by Christians, Muslims, and Jews. To me, the God concept of these traditions strike me as more likely. The theistic God is one that is transcendent over and above creation, existing eternally beyond space and time, and who is the creative agent responsible for creating the entire universe with all its natural laws. Thus, rather than progress in the sciences making such a deity irrelevant it would seem, to proponents of theistic worldview, to be quite the opposite. The further the sciences progress the more human beings learn about the creative acts of God, the deity they believe is responsible for the beautiful complexities in nature and biology, from the immense fine-tuning of the cosmological constants to make the universe compatible for biological life to the biological organisms themselves and the wonders of DNA.
Far more needs to be said concerning the theistic God concept, as challenges have been raised to it too. For example, in the religious texts of these theistic traditions, we might derive an image of a God who seems far from a perfect being. But least on an intuitive level, theism seems to me a more likely belief than with what we find with the ancients who held to their many contingent deities.