The average atheist believes atheism should be the default state of humanity. We cannot prove God exists, they say, and therefore we should reject belief in Him until evidence is forthcoming. Now, in some cases, even this is insufficient. As popular atheist apologists like Richard Dawkins admit, they tend to only pay lip service to evidence, whereas even the most spectacular evidence for God would be better attributed to madness, or even aliens.
But when they're not being that radically stubborn, many atheists will still say there just isn't enough evidence for God. As some put it, "I just believe in one less God than you".
But perhaps the idea that atheism should be the default is just a little more foolish than it seems. When we put real thought into the issue, we realise that sometimes, denial is the irrational position.
To illustrate this concept, consider four historical figures: Henry Ford (pioneer of affordable automobiles), Thomas Edison (credited with the invention of the first commercially viable lightbulb), and the Wright brothers (inventors of the plane). How do we know these men, who died long before most of us were even born, truly existed?
If I wanted proof of Henry Ford, I would have to look no further than my front drive, where two cars bearing his name are currently parked. I could be stubborn and await evidence that he existed, but in doing so, I would look rather silly. For Thomas Edison, I need only look up to my ceiling. I could ask for proof that Edison really had a hand in it, but I'd be slightly cuckoo. For the Wright Brothers, I could look up to the sky, and it wouldn't be too long before testimony to their existence would pass me by.
If we apply atheistic logic to these four men, their existence is highly questionable. We should default to disbelieving in them, and refuse to shift this position until evidence is forthcoming. But notice the implications of this. When we suspend our belief in these inventors, we are required to come up with an alternative explanation for the existence of their inventions. Our default must be to believe, because the alternative is absurd.
In much the same way, when we "believe in one less God", we are left with quite the conundrum: How to explain the absurdly complex creation in which we live without Him? In reality, we are hard pressed to explain the origins of even a model of the solar system without a designer.
Such seems to be the logic of famed scientist Isaac Newton, who was reportedly involved in the following event. Having commissioned a functional model of the solar system, he sat down in his study. He was joined by his atheistic friend - another scientist - who immediately spotted the model. Upon examining it, he was amazed. When the crank was turned, all of the celestial bodies moved exactly as it was understood that they did in that time.
In his glee, he asked Newton who made the model, to which Newton replied "no one". Assuming Newton had misunderstood the question, the atheist again asked who made it. Newton quickly concocted a story by which the model just happened to form itself naturally. This angered his atheistic friend, who scoffed at the story, demanding to know the genius who constructed the model. Newton's response? "This thing is but a puny imitation of a much grander system whose laws you know, and I am not able to convince you that this mere toy is without a designer and maker; yet you profess to believe that the great original from which the design is taken has come into being without either designer or maker! Now tell me by what sort of reasoning do you reach such an incongruous conclusion?"
Setting aside any possible questions as to the historicity of this particular story, the point stands firm. When we look at even the most simplistic imitations of just about anything in our world, we immediately recognise design. No one doubts that something as simple as a mobile above a baby's crib was created by a human being. Yet, somehow, the universe in which we live is so much easier to attribute to some magical explosion that supposedly happened billions of years ago?
Clearly, then, atheism is an irrational default. Even agnosticism isn't much better. When we look at our creation, the existence of at least one designer seems inescapable. But there are still questions we can ask. The existence of design requires a designer, but it doesn't actually get us straight to the designer.
See, as is proven by the fact Ford is still producing cars, Henry Ford is not necessary. Modern planes do not even resemble the Wright Flyer, so they aren't proof of the Wright Brothers. Thomas Edison is a particularly shaky example, as while his existence cannot be denied historically, what can be denied is how much credit he actually deserves for "his" inventions.
So where do we go from here? Well, first, there are a few key assumptions we must make, starting with our very ability to reason. We must assume these questions can be answered, and that we are the kinds of things that can answer them. This is not something we can accept by default. The Wright Flyer couldn't contemplate its creators, so why should we assume we can? We share our world with many different creatures, yet we seem to be the only ones capable of this level of reasoning (though as a Christian, I of course contend we are not). Even among human beings, reasoning skills aren't evenly distributed. If you want proof of that, just play a few rounds of Among Us in a public lobby. You will quickly lose a lot of faith in humanity.
So on what grounds do we even assume we can contemplate questions like "where do we come from?", "why are we here?", and "what happens after death"? This is actually another thing that makes a lot more sense from a Theistic, specifically Christian perspective.
But ultimately, just as with each of our example humans, the best way to solve this issue is the written record. Everything I could possibly want to know about Henry Ford is committed to writing. The reason we know the Wright Brothers invented the plane is the written record. Even the fact that Thomas Edison might not be all he's cracked up to be is evident from history.
So how do we know Yahweh created this world? After all, there are a number of competing truth claims. Why not Allah? Why not Zeus? There are people alive right now who claim to be God! What rules them out?
With enough dedication, we could go through other religions systematically and show that they're not really worth the paper on which their religious texts are written. But we don't need to do this, for the same reason we don't need to eliminate a billion different people who could have invented the plane other than the Wright Brothers. When we know who invented the plane, we can stop looking.
In the same way, when God Himself steps into human history, we don't need to give our ear to other contenders for even one minute. All we need is sufficient record. This, of course, is what we have with the Bible. Even setting aside the divine inspiration (which isn't entirely wise to do), the Bible records God's dealings with humanity over a very long timespan. In particular, it focuses on His chosen nation, from His promises to the patriarchs, to the ultimate revelation of the foretold Messiah.
Through a series of prophecies, miracles, and other spectacular proofs, Yahweh has revealed Himself to mankind, which is not a claim that can be made by any other so-called god. In particular, unlike any other god, Yahweh took on human flesh. Jesus, the Son of God, walked the Earth, exactly as the Old Testament said He would. During His life, He performed many miracles, fulfilled many prophecies, gave a few more, and, ultimately, died on the cross. Yet, He did not stay dead. Demonstrating His sovereign power over death itself, Jesus rose to life again. This is conclusive proof of His claims to be God.
But even His death was not an accident. See, ultimately, we are what's called "sinners". In various ways, every single one of us regularly fall short of God's Holiness, putting us in a state of enmity with Him. Ultimately, this must be dealt with, but God does have some leeway as to how He does this. The first option is the eternal death of the sinner. But the more attractive option is repentance, leading to eternal life. When Jesus died, He took the full wrath of God for sin so that we don't have to. The key to receiving this gift is faith. In order to become what the Bible calls a "new creation", it is necessary to repent of our sin, and confess Jesus as Lord, believing in our heart God raised Him from the dead.