I think that's a great question! Firstly, I personally find that agnostics are probably the most open minded when it comes to religion. One of my best friend's and I always talk about this, his conclusion is "there is no God as such but there are also things that science can't explain...."
Are you familiar with the quantum physics theory of m-theory and string-theory? Modern physics and non-newtonian theory is suggesting more and more that everything exists as a potential and that the observer (i.e. you and I) has a material impact on what ho or she "sees". Furthermore, there is something in the brain called the reticular activating system whose job is basically to decide what our brain/mind will process as important or true - based on our beliefs and own personal experiences....
What I am saying from all this?
BELIEFS = (EXPERIENCES) + (INFORMATION)^2
Sorry not my formula. Basically a writer I like to read contending that our beliefs are not at all based on "facts" as such but rather on our own direct experience and the information we have processed.
Athiests don't believe in God because they don't have any proof. Or stated differently they have had PROOF that no God exists. To state it differently, if I tried to get you to believe that a big pink elephant was sitting right in front of you, you would think I was crazy - if you didn't see it, had never experienced it and your reticular activating system rejected all information related to this based on previously held experiences processed.
The issue is that those of us who do believe - those of us who are capable of rational thought, relatively well-educated, who have accessed the facts and arrived at a different conclusion, do in fact have "proof". Our proof is based on direct experience.
If you are an atheist and haven't had any direct spiritual experiences, you would be crazy to believe in a God.
Therefore, based upon my own personal knowledge about how the brain works, of modern physics and my own direct experience, I realize that the truth is that atheists experience (i.e. there is no God) is just as "true" and as real as my "truth" that there is a presence and power in the universe that science cannot explain (I'm not attached to names.. you can call it my higher self, God, Budda, The Force, Santa Clause, Harry Potter, etc whatever teh hell ever...).
I read something a while a go that says "when you really find it you won't be able to name it and if you can name it you haven't yet really found it...."
That said, if I were an atheist I would ask myself, outside of the far right nuts in the world, how is it that hundreds of millions (probably billions) of "normal", well informed, etc, etc individuals all are having the same direct experience. I am not suggested nor interested in changing people's beliefs I'm merely saying that being a relatively open minded person if millions of people walked into my room and pointed to the floor and said "look at the big pink elephant!!" I would probably spend some time trying to understand why they see what they see. I wouldn't write them off as "crazy" just like a few enlightened souls about 300 years ago who believed Swedenborg the Swedish scientist who developed one of the first prototypes of a flying machine and concluded "some day man will fly even to the moon....."
IT'S NOT RATIONAL TO BELIEVE IN GOD:
a) if you have had no direct experience
b) don't recognize that most of what we enjoy the today is a result of people who recognize the limits to "rationality"
That's why in your calculus 101 class there's something called "bounded rationality".
It wasn't rational to believe that anything without wings could fly....
It wasn't rational to believe that an earth that clearly looks flat was actually round...
It wasn't rational to believe a transatlantic journey, somthing that took up to 6 months would eventually take some as little as 3 hours....
The list goes on and on. That's why Einstein said "Imagination is more important than knowledge...."
Imagination isn't based what's always "true" at the time or what's "rational"...
.....The fact is that yes many of us believe in Evolution, no we don't take everything in the bible literally, man isn't punished because someone ate an apple, the world is older than 5,000 years....
And yet many atheist extremists are troubled by the fact that there are many normal ass individuals in the world who don't need a book called the bible or some scientists in a white coat to validate our own personal experiences...
Lastly (and the reason why I say I like agnostics) is that very few people are willing to admit that just because they can't see something doesn't mean it isn't there.
The believer won't accept the fact that there is no God - to the atheist
The atheist won't accept the fact that there is a God - to the believer
The fact is that we live in a very fluid reality and it is possible that things can be up and down (at the same time) left and right at the same time, in and out at the same time.....
I mean the average person would say you were crazy if you told them as they lay in bed still at night they were spinning at over 500+ miles an hour (as the earth moves on its axis).
In sum (not to be too verbose) the issue is in my humble opinion that people need to accept the fact that it's quite possible that it's "true" that God doesn't exist and it's also true that God does exist....
HOW CAN THAT BE?
What's 100% based upon the evidence you are now being provided - is this woman spinning to the left or to the right??
The should help you to understand how both your truth and someone else's truth can both be 100%, positively "true"