I want to address why there are so many different opposing views in... everything, but specifically beliefs in God. Note: I will only address the question of the Christian God's existence, so please, let's keep the God vs Allah (Islam context) vs Zeus arguments at bay until we can resolve there being the possibility of a God at all (though, I'm not ignorant enough to think that will ever come to pass). Also, let's try to not let this thread turn into reasons why we should rule out God and vice versa. Rather, I want this thread to simply be about reasons why there is so much confusion on one side or the other, or both. There are specific cases in which it would help to give an example of an argument/theory, so feel free to list those.
I assume the role of defending Christianity in my intentions below (in case it isn't obvious ).
There are many scientists and brilliant people that are constantly hands-on with the physical parts of the universe that believe a God had to have made it; yet, there are many scientists and brilliant people that believe a God wasn't necessary in the creation of the universe. How is it possible that something can seem so obvious to one person, and to someone else it seems that the truth is entirely the opposite? Why does each side so strongly believe the opposite of the other side? Better yet, why, if something seems so obvious to one side doesn't the other side submit and acknowledge the truth? And finally to use literal groups of people: why do atheists have such a hard time convincing theists there is no God and why do theists have such a hard time getting acceptance when explaining the impossibilities of there being no God? You would think that if something is truly obvious then surely it would be "common sense" and would be as simple of a choice as breathing free clean air rather than choosing to not breath at all and suffocating yourself (or passing out). This used to confuse me and for months, it caused a doubt in my mind. The bible gives us the answer to this (and I can narrow it down to one verse) but it's because we are all sinners and we can only be made righteous and wise when we demonstrate faith. This is that verse that says why there are atheists (and try to stomach reading it if you're an atheist so that I can explain how it could be true in just a moment after): Psalm 14:1 "The fool has said in his heart- there is no God." The bible says the ones that have made up their minds (that there is no God) are fools. It sounds like bias bigotry and even hypocrisy at first look (because I even admit there are intelligent atheists), doesn't it? I'll give you the answer that resolves this statement in just another moment. However, really what other reason is there that there are too extremely opposite beliefs in the world: those that believe in deity, and then those that don't? My answer that you've all been waiting for...: the reason there are atheists and theists is because of the sin of those that haven't believed in Jesus Christ who died on the cross for their sins. Sin blinds those that have no faith and they believe the lies they, and others, tell themselves (because "The heart is desperately wicked" as Jeremiah 17:9 puts it) and try to excuse any flaw in their belief or beat-around the bush (as it appears sometimes) in a way to avoid answering it (whether knowingly or unknowingly). Once you accept Jesus Christ's free gift of salvation, you no longer have to pay the price for your sins (and only one sin is necessary to put anyone in Hell, and according to the Bible- we have all sinned except for Jesus). My belief about this whole subject of confusion is also the belief of the bible- which, by the way, is something that atheists think some lunatics put together. To me, this whole subject seems like the most intelligent thing that was ever realized by humans- that being there are so many different opinions to important subjects. We know that everything only has one truth/answer (it would be a paradox if two opposite truths explain something at the same time, in this dimension) and all the sides of an argument can't all be right, in this dimension. The answer is sin and our humanly nature. Atheists don't have a reason for this that makes sense (unless you can prove me otherwise- and I genuinely want to know the flaws of this argument before using it in further debates). Atheists could call us fools as well, but if nothing is blinding us spiritually (since, to atheists, the spiritual realm doesn't exist), what is interfering with our logic to understand their arguments? Are all believers in deity lunatics? If so, atheists are going to have to open many many many more psychiatric hospitals. Either 80% to 90% of the world doesn't have the capacity to see atheists' logic (supposedly obvious and as easy as pie) or the entire human race is polluted with sin and only those who are redeemed can see the truth. I think, quite obviously, humans aren't literally dumb. I think that we're all capable of working out the process to logically determine what truth is and what truth isn't. The only plausible reason I've seen is sin and, because of it, we're all just blinded to some extent or another and can't determine how blind we are- this is why I believe we must rely on the Bible to tell us what the truth is. Once again, I also have my reasons for knowing that Christianity is the one true "religion", so let's save my time and work out this problem first.
Sources: 80%-90% theist population... Google it; and that's generous- considering some studies say only up to 2% in North America are Agnostic/Atheist.