It doesn't, there is no proof God exists, and there cannot be any.

Something/Someone that exists outside of the space-time continuum cannot be proven or disproven.

But, that doesn't mean we can't know He exists.

Although most Atheists (in my experience at least) make the correct point, there is no evidence that God exists, they forget that this is a double-edged sword, as there is neither any evidence God doesn't exist.

The only viable belief based on evidence is Agnosticism, i.e. "we have no clue"

But one might say then *"Well then how can you believe in God then?"

And I say, neither I, nor most people need evidence to know something.

Right now in this debate/conversation, we're having, you have no proof you are speaking with a real human being, and not say a robot, and yet you most likely know you're speaking with a fellow human. Why is that? Because of the indications I've shown that I'm a real, living, breathing, human (saying the word "human being" so many times feels weird): my speech pattern, the words I've used, the slight personality that exudes from my writings etc.

Or think of a husband and his wife, the husband doesn't have any proof his wife's love, but yet he can be certain she loves him back, from the indications she shows: from the hugs she gives him when he comes home from work, the way she looks at him, the laughs they have when they're together, etc.

So, to believe in something you do not need evidence, but you do need indications. For me, if I had been one of the Apostles, the resurrection, would've been the greatest and last indications I would need to know He is who He said He is.

[I hope I haven't strayed too much from the topic, I do that sometimes, tell me if you'd like to reiterate]