Doubting the existence of God is akin to doubting the existence of one’s wife or children.
What if I suffered from untreated chronic mild depression? It is chronic, in that it doesn’t ever go away entirely, but mild in the sense that I suffer no physical symptoms: many people with more severe forms of depression suffer from odd pains and illnesses. Additionally, severe depression is usually characterized by an inability to function. I suffer no physical pains or illnesses. I’m quite healthy. And I continue to function, even in social settings. However, I do tend to be withdrawn.
The other odd aspect to my depression is the regular feeling I have that my wife and children do not love me or even like me, that in fact they would prefer not to have to be around me. More generally, I am convinced that I have no friends and I believe without a doubt that people would prefer I not talk to them or interact with them in any way. I therefore tend not to talk to anyone unless they talk to me first and then I limit my conversation to simply responding to what they have asked in as few words as possible.
I am convinced that I am a failure and a loser.
My beliefs, most people would say, lack objective evidence, but no evidence that people may bring to bear to try to dissuade me from my point of view will have any effect on my core belief. I can find explanations and evidences to explain away anything they tell me that would seem to contradict my core beliefs.
While it is ludicrous to imagine that one’s wife or children don’t exist, or contrariwise to respond when something happens that, “so my wife does exist after all,” for instance if I discover supper has been prepared for me or my clothes have mysteriously appeared in my drawers all clean and folded, it is equally as ludicrous to harbor such thoughts regarding God. To think that he needs to be proven to exist is silly and even more silly—or sad—is to imagine that he doesn’t exist. Just as my belief that I have no friends or family is irrational, the product of my mental illness, so the Bible comments that those who disbelieve in God are “fools.” It is no different than not believing in your neighbor. And since it would be very peculiar to develop philosophical “proofs” for the existence of your wife—say a teleological, ontological, first cause and the like for her—so I would argue it is equally as silly, and equally as much a waste of time and energy as it is for someone to try to prove God’s existence. You’ll no more convince skeptics that you’re right than you’ll be able to convince me that anyone gives a damn about me. And those that believe in God, like those who believe they have friends, don’t need any convincing. You already know it.