" The True Believer ignores anything that doesn't fit his belief system. Instead, he inevitably comes to hold those beliefs at a very profound level. They can become absolutely part of his identity. It is this that brings together the religious, the psychic, the cynic (as opposed to the open skeptic) and the narrow-minded of all kinds. It is something I encountered a lot among my fellow Christians. At one level it can be seen in the circular discussion which goes as follows:

Why do you believe in the bible?
Because it is Gods word.
And why do you believe in God?
Because of what it says in the bible.

At a less obvious level, it can be seen in the following common exchange:

Why do you believe Christianity is true?
Because I have the experience of a personal relationship with God.
So how do you know you're not fooling yourself?
Because i know it is real.

Even as an enthusiastic believer myself I could see this kind of tautology at work, and over time I realized that it is common to all forms of True Belief., regardless of the particular belief in question. The fact is, it's enormously difficult - and you need to be fantastically brave - to overcome the circularity of your own ideologies. But just because our identity might be tied up with what we believe, it doesn't make that belief any more correct. One wishes that True Believers of any sort would learn a little modesty in their convictions. "

― Derren Brown , Tricks of the Mind