"One day when I was about 8 years old, I was drawing the crucifixion as part of my Bible studies homework. I loved art too. And nature. I loved how God made all the animals. They were also perfect. Unconditionally beautiful. It was an amazing world...
But anyway, there I was happily drawing my hero when my big brother Bob asked, “Why do you believe in God?” Just a simple question. But my mum panicked. “Bob,” she said in a tone that I knew meant, “Shut up.” Why was that a bad thing to ask? If there was a God and my faith was strong it didn’t matter what people said.
Oh…hang on. There is no God. He knows it, and she knows it deep down. It was as simple as that. I started thinking about it and asking more questions, and within an hour, I was an atheist."
I think most people have similar moments in their lives when they realize on some level that god is a myth. The question is whether they are emotionally able to accept it. Do they have the self-confidence to admit they were wrong, even duped? Or does their emotional need to pretend they are perfect (or nearly so) prevent them from admitting it--perhaps even to themselves.
What separates people into categories such as believer or non-believer is how they react to this epiphany, which tells you a great deal about the person. Non-believers accept it. Their primary interest is knowing the truth. It doesn't occur to them to reject something that is true--regardless of how they may feel about it or how it makes them feel about other things. They may, at some point, decide just how certain they are and whether they think of themselves as atheist or agnostic and whether they should ever mention it to anyone else, but they accept, more or less, that it is true that god is literally myth.
Another category includes those I have mentioned before: psychopaths and future "leaders". They realize that religion is a tool they can use to control people and file that information away for later use. They do NOT tell anyone because that would make it impossible for them to use this new insight to control others and they instantly recognize that telling would give someone else power over them--which is something they cannot abide.
Some ostensible believers come to this realization but decide to keep their new knowledge secret because they think religion is good for others and they don't want to undermine the system. Many decide to keep quiet out of a well justified fear of how the religious will treat them if they are found out.
True believers refuse to accept it.
Why would they refuse to accept it when it is, for a moment, clear to them that there is no more evidence for their god than for any of the false gods? When it is, for a moment, clear to them that many of their elders and authority figures know this is true on some level and are simply fooling them?
I think the most common reason is the inability to accept that they have been fooled or mistaken. Their egos are too fragile to allow them to face this fact. A second but related reason is their inability to accept that their loved ones and authority figures are wrong or dishonest. This, too, is an ego-based refusal to accept reality.
The longer the parents and clergy can put off the moment of truth, the better--from their viewpoint. Because the longer the charade has been played on the believer, the more difficult his ego finds it to accept that he has been fooled--sometimes to the point where the believer's ego becomes a willing participant in the charade. If the believer's ego is already intricately connected with his religion or with a need to believe that he is intelligent (too intelligent to be fooled), then this epiphany will be quickly rejected. In fact, the believer may not even be able to consciously contemplate it in any significant way.
I think there are a couple of other categories of believers: First, those so completely ensconced in a cocoon of family and community that they are completely cloistered in a world where only their religion is present as a world view--except perhaps in a few books or on the world news. Such people are becoming more and more rare as the internet and television have reached almost all corners of the globe, but I have met a couple of people in the past who seemed to actually fit this description.
Finally, there are those who literally lack the mental capacity to question what they are told. I don't know how many such people there are. I used to think they were legion, but I have learned that most people as they age will reach a stage sooner or later where the epiphany of reality occurs.
Believers in these last two categories, however, will also be motivated by a certain amount of egotism and thus may, for practical purposes, fall into the category of true believers in denial because their reaction to non-believers will be indistinguishable from that of ego driven believers. Those who keep quiet out of fear and those who are part of the religious power structure will also react to atheists as they think they are expected to react. Some of them may be well intentioned because of their false belief that religion is necessary for morality, but the end result is the same: Whatever their internal thoughts on the matter, the majority of believers will act as if their religion is intrinsically bound up with their egos. Their defense of it will not be based on reason but will be a matter of pride.