I've been trying to figure out how to believe in God for a while now, and I always end up questioning my own motives. For one thing, I end up thinking that wanting everlasting life or just to have something in common with people who share my political views and moral values might be selfish.
I also get very caught up with the difference between wanting to believe in God, hoping God exists, and actually believing with certainty and knowledge that God exists. I've been in the first two situations many times, but I don't know that I've ever been in the third one. And I suspect the third one is what I would need to be able to call myself a Christian.
I'm a very philosophical person, and I end up coming very close to believing and stopping just short of actually believing in the supernatural. For instance, I start thinking about how most people are willing to do horrible and immoral things if they don't believe in a higher power, and how a lack of Christianity can lead to people relying upon externalized morality to the point that if they can get away with something, they'll do it because no one is watching them or because society doesn't currently regard it as wrong. I see the immorality and the degraded lifestyles a lack of belief produces in people. I can understand why it is a social good for people to accept the Christian religion and follow the moral codes suggested by it.
I also think about things like Plato's theory of forms, and wonder if simply the fact that the concept of God exists in our minds is enough to prove his existence. But then I realize that this doesn't point to any particular god, and may only be proof that there exists some sort of higher power without telling us anything about its nature. It also potentially suggests that God's existence is dependent on people believing in him or upon people existing to perceive his existence, which would seem to be an inappropriate conclusion.
As things stand, I find myself thinking I must be an Agnostic, because I'm always wondering what sort of higher power exists, and whether I just want it to be the Christian God because that falls in line with my culture... or whether it's actually plausible that this is more correct.
I keep trying and failing to come up with something that holds up to my own intellectual scrutiny. One time, I even reached as far as wondering whether "The word was God," means that the text and the ideas of the Bible itself are God, and that the eternal life promised to believers is actually related to being remembered or recorded by future generations somehow. I know that's quite a reach and probably wouldn't be acceptable.
So my question is, what do you have to do or believe in order for it to count as believing in God? Also, how do you get to a point where you can know that God exists and not doubt it?