I was recently thinking about the topic of “belief.” Why do people believe what they believe?
Seventeenth century mathematician and Christian philosopher Blaise Pascal is often quoted as saying, “People almost invariably arrive at their beliefs not on the basis of proof but on the basis of what they find attractive.” I bet Pascal was probably thinking of the modern, American teenager when he wrote this (but undoubtedly there are some adults who meet Pascal's description as well).
So what does it mean to “believe” something, and how to people arrive at their beliefs?
Philosophy describes knowledge as “justified true belief.” Belief, then, is the attitude we have towards something we take to be the case or regard as true. When we are young, we often believe things because we are taught them. Parents, grandparents, teachers, and others influence our beliefs. This “appeal to authority” may be adequate for a child; but as adults, we need to move away from this way of thinking.
Now an important point here: This does not mean we should discount authority or information we gain from others (e.g.: eyewitness testimony). Personal testimony is a legitimate source of knowledge. There are very few people who believe, for instance, that the Apollo moon landings were faked. Anyone under the age of 45 probably has no real memory of the actual events. Yet the vast majority of Americans believe American astronauts really did land on the moon. How do they come to those conclusions? Personal or eyewitness testimony! The scientist, astronauts, news reporters, and the general public who were witnesses to the events are still alive to describe them, even though the last Apollo mission happened some 43 years ago.
So what is going to happen in another 40 years when all those eyewitnesses are dead? Will people start doubting the veracity of the moon landings? Certainly not! We have a wealth of photographs, videos, and other written documentation that describes in great detail the events. Even 100 years from now, future generations can be confident of the events of the Apollo moon landings.
In my own growth as a Christian, I confess when I was a teenager and young adult, I believed Christianity, in part, because that was how I was raised. I do believe that a belief in God is a properly basic belief; however, I also had a strong desire to know the truth. While I believed in God and my Christian experience, I had a strong desire to know truth and did not want to believe something that was not true. This lead me to the world of Christian apologetics.
Now, after some 15 plus years of study, my belief in the truth of Christianity is quite strong, indeed.
 Stanford Encyclopedia of Philosophy, http://plato.stanford.edu/entries/belief/