that the assumption or acclaim could only be falsified to determine it's 'Not Wrong' status from before till present. It cannot and would be impossible to direct prove it's direct correlation for things unperceived or in the future.
Even though Bible acclaims the only words of God. However, without enough knowledge on God itself, we are unable to determine truth of this.
Judging from the system of determination, we are not in the set to study the question of God. Thus, it results eternal failure to have 100% sure proof of the existence or non-existence of his presence.

The only thing you can rely on is the thing called faith, which is purely psychological belief of something to be 100% true from partial facts.

I've seen people turning from Buddists to Christian and vice versa. It did not really change the world much. Sometimes, I really feel that Christians are wasting to much time doing their service and forget to help those who really wants some help in their life. Although you might call the belief of God a solution to every problem, the real thing people wants is a piece of bread to sustain the pain God give us. Ironic I found it!
Last not least, just for your information, a real Christian should just go to middle east to do preaching as that's the one of the toughest job in the world indeed.