“Now, faith is the substance of things hoped for; the evidence of things not seen…. By faith we understand….” (Hebrews 11:1ff)
There are good reasons not to believe in God, not to believe in Jesus, and not to believe in Holy Scripture.
A wise servant of the Lord will want to learn what they are and why people hold on to them. In doing so, he will better understand his own belief and will be able to respond to the questions/attacks of unbelievers.
This is far more important than the typical Christian realizes.
We cannot effectively counter the resistance of the unbeliever–whether he/she is a seeker, an agnostic, skeptic, atheist, or full blown antagonist–until we learn why they reject the heart of the message of the Christian faith.
Faith. It starts with this and perhaps ends there also.