I believe choosing what to believe in terms of having adhering to a religious belief or discounting any and all religious belief is a choice that can be made. Not everyone raised into a certain belief system blindly believes what they are being taught, and some people do question their belief system as adults when they are older and wiser to understand the distinction between fantasy and reality. What triggers the questioning and onset of dissent from belief, however, could be due to any number of factors.
"Never trust a fox. Looks like a dog, behaves like a cat."
~ Erin Hunter
~ Erin Hunter