2. God is God, not something to be examined & assessed.
"I am who I am." God, Exodus 3:14
God ultimately needs no justification. This is just logical and axiomatic, since God is God. If he needed to be justified then he would not be God. He is not a thing to be studied or an idea to be proven. He cannot be judged in any meaningful way by humans since he is the judge of all humans. Human judgements about God are merely part of the judgement of God on the person themselves. A microscopic organism arrogantly staring up the microscope, shaking its fist, is engaging in a futile exercise. It is merely sealing the judgement by the one who is looking down the microscope at the organism.
A person on trial in the law court can potentially appeal to a higher court if they object to how the judge is dealing with them. However, there is no higher court than God. He is the supreme, supreme court.
Christians rely on the self-authenticating role of the Holy Spirit to confirm God's existence to them. Imagine there was another kind of authority to which humans could appeal that could pass judgement on God's existence. It would have to be a higher authority, which is impossible since God is the highest authority. Appealing to the authority of human reason is placing human reason as supreme over God. This is only going to prove or disprove a caricature 'god' that doesn't meet the definition of the supreme 'God'.
That is not to say that there is no role for argument and human reasoning. These do have their place – not as master but as servant to the supreme authority of God's Word through the work of His Spirit.
Science can describe the mechanistic functions of humanity's unique behaviour in the world: rationality, morality, art, aesthetics, wonder, awe, self-awareness, self-reflection, longing for justice, empathy, creativity and a sense of eternity. Science does not however, answer the ultimate question of their source. We do not argue up from these things to therefore conclude there is a God. Rather, the starting point of the truth of Christian theism allows us to see these things as a logical consequence. C.S. Lewis famously said, "I believe in Christianity as I believe that the sun has risen. Not only because I see it, but because by it I see everything else."
John Calvin reflected on the Bible and human experience. He explained the idea of 'sensus divinitatis', or the 'sense of the divine'. From Romans Chapter 1, we see that humanity as a whole is aware of God and therefore without excuse before him. People are described as suppressing the truth about God, exchanging the truth about God for a lie and not thinking it worthwhile to retain the knowledge of God. We find all these things happening in the world.
The near universal view of humanity throughout history has been the acceptance of there being more to reality than just the regular physical world that we see. The vast majority still believe in a God. Despite heavy-handed regimes in some countries, trying to stamp out belief in God, it has resisted extermination and often thrived. Despite the forces of Western secular societies' assault on the traditional churches, the statistics still reveal a great majority rejecting materialism. Most still believe in a God. Humanity as a whole has voted with its feet, rejecting materialism in favour of God's existence. Like it or not, this isn't about to change.
Psychologists, particularly atheist ones, come up with all sorts of disparaging terms like Hyperactive Agency Detection Device or HADD – as in "I've been had!" Studies do show the human ability to go beyond the raw data to posit patterns and purposes which sometimes don't correspond to reality. Often, however, they do correspond to reality. They are valuable parts of our ability to do many things such as posit danger, enable empathy, connect socially and plan the future. There are many other positive benefits and necessary functions. Surely a God would include a faculty in humans for them to think about him and connect with him.
Though human reasoning, memory and a good many other faculties are fallible, no-one is denying that they can function properly and serve good purposes. Atheists merely smuggle their conclusion into their argument – they assume that our cognitive faculties are misfiring by producing belief in God because they assume he isn't there. Theists are just as justified to say our faculties are working properly when they produce belief in God since he is there. The question of God's existence is a separate issue from brain function.
Ironically, what we can conclude from these psychological studies is that caricaturing Christians as mentally deficient is contrary to the evidence. Their brains are certainly not being faulty when they produce belief in God – they are engaged in healthy, normal function – the same category of psychological functions that all healthy humans engage in. Drawing analogies with belief in the Tooth Fairy or Santa Claus may get a laugh from fellow-atheists but it's an unjustified comparison. It's just as unfair to lump all 'belief' in together as it is to lump all 'skepticism' in together: for example "atheists are like dumb skeptics who deny the moon landing and the death of Elvis." Saying that is unjustified unkindness that gets us nowhere.
Philosopher Alvin Plantinga in 'Warranted Christian Belief' argues for the concept of 'properly basic beliefs'. These are ultimately unprovable first principles by which we operate as humans. They include beliefs such as the existence of other minds and belief in the existence of the past. We can only experience our own mind, never another. The movie 'The Matrix' explored one alternative – that we are what the philosophers describe as a 'brain in a vat' merely connected to complicated stimuli which gives us the allusion of reality and other minds. In the Matrix, Mr Anderson interacted with computer control programs whom he assumed were real people. I can never ultimately prove that I am not in that situation but my 'properly basic belief' is that I'm not.
Other fields have foundational, unprovable beliefs or axioms. Scientists must assume the uniformity of nature and the regularity of nature. You can't prove that the stuff that happens in one place at one time will also work the same in another place and another time.
For Christians, God's existence is a properly basic belief. Though there are many Christian philosophers who hold their own in debates about God, many Christians find this hard, just as many atheists can find formal arguments hard. The point is that though Christians may not be able to refute the great philosophers of atheism, neither could anyone when it comes to refuting our presence in the Matrix and a number of other basic axioms in life. No one can.
The scientist and philosopher of science Michael Polanyi demonstrated that we have much knowledge that we can't articulate. A person may not be able to describe how to ride a bike or why it doesn't fall down. Yet, they can know these things thoroughly without explaining them. We know more than we can articulate.
No-one else can enter a human's mind. Many people have knowledge of God as one of their properly basic beliefs. For them God's existence is just axiomatic and undeniable. Ultimately they may not be able to articulate exactly why they accept God's existence, even though some ideas may bubble to the surface like, "How could something come from nothing?"
Imagine if no-one believed that you had slid head first on your back down the highest ski field in North America. You would still be justified in believing it if this did happen to you. You may perhaps have no objective proof because it was a personal, unrepeatable experience. Despite the disbelief of others and your lack of proof, you would actually be irrational to stop accepting its truth just because others doubted it. That is how it is for Christian theists when called upon to justify their belief in God. How can a theist relinquish their intrinsic, properly basic knowledge of God just because others challenge it.
The burden of proof does not necessarily rest with the theist. For multitudes on the planet, it is just intuitively obvious that God "is who he is" (Exodus 3:14).