Oh, that question is way too difficult to answer briefly. We're talking book-length essays here.
But I'll try with a short answer:
I want to believe in God. I really do. And an afterlife.
It would be so great -- so reassuring, so comforting, so peaceful -- to know that there's Someone out there who's in control of a world that seems so out of control. That, despite all appearances, all things really do work together for good to them that love God. That an Eternal Reward awaits all of us (or at least, me) in a future life to compensate for all of the crap we have to put up with (some more than others) in this one. That in the end, I can look back on my existence and rejoice that all the balances are added up and everything has worked out to be just and fair.
This is just what religion (just about any religion) promises.
Except that it all sounds *way* too good to be true.
And if there's one thing I've learned in life, it's that if something sounds too good to be true, it probably is.
Of course, it might not be. Let's consider the possibilities.
Ah, but that's where things get really hairy. There are so many possibilities, and God has done a really miserable job of making Himself(1) clear about which ones are the right ones. Each possibility has its share of adherents, all of whom are convinced (by the spirit, or by some analogous means) that their beliefs are the "right" ones.
(Footnote 1: In this essay, I will chauvinistically use male pronouns to refer to Deity, because it makes the narrative flow more smoothly than saying He/She/It/They all the time. Apologies in advance.)
So, searching them out by the spirit doesn't tell us anything, since the spirit is demonstrably telling one thing to one person and another thing to another person. How about logic and reason? Well, logic and reason are no help, because each one of these belief systems is demonstrably self-contradictory in one way or another. And what's more, the adherents of those belief systems don't see those things as contradictory at all -- they have found ways to explain these things away so that they don't seem like contradictions after all ... not to the believers, anyway. One example: two books of the New Testament say that Mary saw one angel at Jesus's tomb, and two more say that there were two angels at Jesus's tomb. How do we resolve this? Clearly, there *were* two there, but Mary only *saw* one of them. It all makes sense ... if you believe.
Ah, and that's really the bottom line, isn't it. Logic and sound reasoning are "misleading", and even spiritual witnesses aren't reliable -- but that leap of faith, that will answer all your doubts. Just believe. As I've been told so often, "Seeing isn't believing; believing is seeing." ... which is a clever way of saying that "we who are believers, we don't let troublesome contradictions get in our way; we've made that 'leap of faith', which renders doubts and contradictions irrelevant. God will make everything clear, in His Own good time. Ours is not to reason why, ours is but to sit quietly and wait for the Second Coming (or some analogous occurrence), at which time, all these things will be made clear."
Sorry, but I just can't buy that. If there is a God, He wouldn't have discontinuities that would need explaining, or at least, He wouldn't wait forever to make them understandable to the average mortal mind. If there is a God, He wouldn't *want* me to suspend reason and doubt and critical analysis for the sake of a "just believe, and that will make everything all right" mentality -- on the contrary, He would welcome questions and doubts and fears, and would explain them clearly and understandably. He loves me, after all, presumably, right? He wants me to know the truth. So why all the (apparently deliberate) secrecy? He's my Parent, after all, in at least some metaphorical sense, right? Why then does He act so much like an absent father?
If God could create the universe, God could speak to me and help me understand Him. God wouldn't need a spokesperson, and wouldn't need a book, and wouldn't need a Holy Spirit. If God wants me to know Him, He knows where to find me.
Until then -- to be truthful -- I'm really better off trusting in the good old arm of flesh. The arm of flesh doesn't let me down. I pray to God, asking for guidance, and what happens? Nothing. I trust in the arm of flesh -- work hard, keep my nose clean -- and I get ahead in the world. I pay tithing, hoping that God will open the windows of heaven, and what happens? Nothing. But if I put that 10% into my 401(k), now I've got a retirement to look forward to. I believe that God created the world in 6 days, 6000 years ago, and how does that help me understand the observable universe? Not at all. On the contrary, it forces me to come up with clever theories about how the light from stars tens of thousands of light years away is already arriving here on earth, and how dinosaur fossils can be millions of years old, and on and on. But if I believe that the universe is billions of years old, that it evolved into what it is now -- then the observable evidence fits neatly into place and makes all kinds of sense, thank you.
In the end, I've been unable to discover any system of belief -- Christian or otherwise -- in which God can exist without colliding with observable evidence in significant ways.
And so, after looking for God using logic and reason, using blind faith, using spiritual witnesses, using written scriptures -- in short, using any and all means available to us -- God simply fails to emerge as a viable concept, much less a living, breathing, existing being.
I really want to believe that there's Someone out there who will make everything all right. I suspect that we all do. I suspect that it's built into us, a holdover from our childhoods. But eventually we have to grow up, and face facts. There is no one out there who has all the answers. We're on our own for that. I have come to the conclusion that the sooner we get ahold of that and hang onto it, the happier we will all be.
Brian C. Madsen [an error occurred while processing this directive]