If we affirm that the deity of God exists, then we affirm the existence of the Being of God. It is the same as admitting the personhood of another man exists along with his existent state. What I mean by the latter is the very fact that the man exists, and all that goes with that proof that he is existent. However, along with that existent state comes, by definition, certain traits. Is he of European, African or Asian descent? How many years has he lived? What is his ethnicity? What kind of language does he speak? What kind of dialect of this language does he have? The list goes on. These are all traits specific to him, which affect his personhood.
Logic compels us to deny that a man can, outside of his existent state, possess any trait other than that compelled by force of means. An Asian man cannot suddenly become of African descent (as scripture asks, can an Ethiopian change his skin?; Jer 12:23), nor can a man who has lived seventy years suddenly become ten years old. For sure, he can temporarily change certain traits (a white man can take medication that will temporarily turn him black) or add to his current traits (a man who speaks French as a native language can teach himself German), but that which is part of his existent state cannot be removed from him.
Now we will give application of this to God. If we admit the deity of God, along with the Being of God, then it follows likewise that there must be some traits pertaining to that Being of God. That is, what is God's make-up? We will recognize that God is outside of certain limitations as found by a mortal man in his existent state - however, this does not mean God is not without traits pertaining to His Being.
Let us see this in application, with the definition of a personal God. Let us take two men who see God in their own personal ways: one sees God as a divine force - a vague kind of karma - whereas the other sees God as a therapeutic deistic version of the God of the Bible (all of the morals and ethics, but none of the accountability or authority). On the one hand, God is a vague force that simply keeps the universe together, similar to the Force of Star Wars; on the other hand, God is a rational, functioning entity who speaks, reasons, and interacts with creation, even setting down rules for it in a somewhat orderly. Both, however, are entirely different gods.
Let us put this in another application. Suppose we place a Muslim together with a Christian: on the one hand, God is a unitarian Being who is completely unable to take part in creation; on the other hand, God is a Trinitarian Being (Father, Son, Holy Spirit), with the second Person in the Trinity having taken on flesh and dwelt among mankind, representing a God who is far more interactive with His creation than the previous. These are, again, entirely different gods.
If we affirm the deity of God, we have to likewise affirm the Being of God. If we affirm the Being of God, we have to affirm the individual traits which compose God's very Being. Just as a man cannot contradict his existent state, God cannot contradict His entity. That is, God cannot be Trinitarian and Unitarian at the same time any more than He could be solely Creator (as found in monotheism) and solely creation (as found in pantheism) at the same time. To uphold that God is both Unitarian and Trinitarian is to present a contradiction. The deity of God cannot by definition be made up of a contradiction.
Therefore, those who would uphold that God is merely a personal God, from whom one can imagine their own definitions, are not teaching a coherent or logical definition of God. Rationally speaking, the personal God does not exist, because His very Being, logically, could not exist. It would be like a policeman writing down reports of a burglar from two witnesses, with one witness describing the burglar as a young white male, with the other describing an older black female. The policeman would have to logically conclude that either both witnesses were lying or one of them was in error - the burglar could not have been both a young white male and an older black female. This is why, in some regards, I am sympathetic to atheists who are responding to this plethora of ideas. For many, atheism is merely the rational conclusion of postmodern theology: if there are many gods, and there is no standard by which to define God, then, logically speaking, there can be no God.
Now let us recognize the main source of this concept of a personal God: the individual person. It comes from the individual's postmodern opinion manifesting itself in theological form. This is a weak basis at best, and is based entirely on fallacious logic. In attempting to justify all gods, the individual simply justifies no gods. What this does is transform the personal God into an impersonal God, because the personal God's existence is not a deity interacting with humanity, but humanity creating a God of its own design. This God, however, has no power. He is unable to do anything. With no existence of being, there are no discernible traits or qualities with which He is able to interact with His creation. He is powerless and unable to do anything with His creation. His very existence, in fact, is completely reliant upon the creation.
These are, of course, all the traits of an idol.
There is a story within Jewish tradition (reinvented in the Quran) where Abram (before being chosen by God) shatters all but one idol in his father's shop, then tells his father that the one idol did it. When the father replied that this was impossible, Abraham pointed this fact out, and showed that the idols had no powers at all, and therefore could not possibly be worshiped.
Isaiah likewise mocked idolatry, showing how with one piece of wood a man makes firewood to cook and then creates an idol to thank him for the food.
Surely he cuts cedars for himself, and takes a cypress or an oak and raises it for himself among the trees of the forest. He plants a fir, and the rain makes it grow. Then it becomes something for a man to burn, so he takes one of them and warms himself; he also makes a fire to bake bread. He also makes a god and worships it; he makes it a graven image and falls down before it. Half of it he burns in the fire; over this half he eats meat as he roasts a roast and is satisfied. He also warms himself and says, "Aha! I am warm, I have seen the fire." But the rest of it he makes into a god, his graven image He falls down before it and worships; he also prays to it and says, "Deliver me, for you are my god." [Isaiah 44:14-17]The uniqueness of God is declared by the Lord: "I am the first and I am the last, and there is no God besides Me" (Isa 44:6). He likewise says: "Is there any God besides Me, or is there any other Rock?" (Isa 44:8) Those who seek after idols - be they tangible or mental - are simply seeking to "pray to a god who cannot save" (Isa 45:20). A personal God - as we have demonstrated - has no personal qualities nor discernible traits. Therefore, the personal God is one who cannot save. A personal God who cannot save is as impersonal a God as they come.
What likewise makes this impersonal is that we are removing God's sovereignty over His own standards and replacing them with our own. The Lord said to the Israelites: "You shall not add to the word that I command you, nor take from it, that you may keep the commandments of the LORD your God that I command you" (Deut 4:2). Christ likewise said: "You are my friends if you do what I command you" (John 15:14). Yet those who would care to pick-and-choose what verses or commands to follow are disobeying God, even if they think they are still obeying God's commands by obeying part of His commands. Yet if our parents told us, as children, to mow the lawn and then clean the kitchen, and we only did one of those two chores, are we not still disobeying our parents? So too are those who want to acknowledge Christ's command "love one another" (John 15:17), and yet want to ignore or His statement "no one comes to the Father but through Me" (John 14:6). Christ staunchly warned us, however, that we were to obey all His commands, and told His disciples: "For whoever is ashamed of Me and My words, the Son of Man will be ashamed of him when He comes in His glory..." (Luke 9:26).
But as we said, the proponents of a personal God are placing themselves as the authority over God, usurping God's sovereignty for their own. Many will deny they are doing so (often emotionally), but this is the logical conclusion of their own theology. It is a very man-centered theology, and perhaps one that represents a reversed kind of monergism: that is, the authority of man is supreme over the authority of God. Creation, however, cannot in any way usurp its creator. As the apostle Paul wrote: "The thing molded will not say to the molder, 'Why did you make me like this,' will it?" (Rom 9:20). Man has absolutely no right to redefine God, just as the clay has no right to try to mold the potter. For us to attempt to do so is merely a sign of our heathen tendencies, in which we know God but do not honor Him as God, becoming futile in our speculations, and professing to be wise, people only become fools (cf. Rom 1:21-22).
Therefore, we have discussed a few things regarding those who want us to just seek after "our own personal God":
- It contradicts the very nature of a true Being, implying that a Being can be two things at once.
- It is sourced not to revelation or sound, consistent theology but to an individual's own personal preferences.
- It is the very definition of an idol, and hence worshiping this god is simply idol worship.
- This "personal God" has no ability to save, and no way to communicate with the individual. He is, for all intents and purposes, a useless god to whom to pray.