Christians say we are saved by faith/believing. OK, then I have a question. How much faith SAVES YOU? Can you have a little doubt or a lot of doubt mixed in with your belief? The answer is yes. When I took my first step toward God, it was with mostly doubt and just a grain of belief.
So, how much faith saves you? How strongly do you need to believe? You need only enough faith to ASK God to give you a clean slate regarding your sin (falling short).
Think about it. It does take at least a tiny bit of faith to make this request of a God – a God you 99% believe may not even be there! If you had, say, just a 1% belief that the Christian story is true, this 1% can be enough that you would ask God to be saved. But, if you had 0% belief, you would never even THINK to ask the God you think isn’t even there, to save you. It would never cross your mind.
The story of the Woman at the Well proves to me that saving faith = whatever small amount of faith is needed to make one ask God to be saved. If this matter troubles you, we should talk.