When the light of logic shines brightest upon the cockroach of religious justification, it often attempts to scurry under the refrigerator of "incomprehensible mystery" for some impregnable threshold of safety. When all arguments from ignorance have been educated into exhaustion you can almost finish the sentence of the desperate and defeated theists as they utter something to the effect of "you're just a human, and you can't understand God. He works in mysterious ways beyond our comprehension. Who are you to question him?"
I am perplexed, not by the power of this argument, but by the combination of its popularity and absurdity. These people consider their undetectable God too complicated, and mysterious for the people who don't believe in it to comprehend. If you hold that position alone, it's fair enough, but it's not fair to simultaneously consider the ambiguity and utter lack of physical evidence as proof of your God. Additionally, it's ludicrous to assume that while he's too supreme and supernatural for doubters to grasp or detect, YOU somehow are able to understand that same being well enough to not only claim it exists with great certainty, but also claim that YOU understand its actions, desires, intentions, and emotions. One group of humans simply cannot tell the doubting humans that God is too complex to comprehend before preaching to them about just how well they understand him. Surely is particularly out of place for discussing their "personal relationship" with such an incomprehensible being.
In addition to this claim's base lunacy I must ask what other religion or non-falsifiable claim can the "too hard to understand" angle not be applied to? If you're a Christian, for example who claims that Hindus should believe in your God because their disbelief in your God is rooted in him being beyond their level of human comprehension, what's to stop them from claiming the same of their God in application to you? What's to stop me from claiming I have an invisible, intangible pet pterodactyl on my shoulder, but you can't tell it's there because its power is beyond what you can imagine and it doesn't wish for you to detect it, so you can't. You would be inexpressibly gullible to accept my claim as true, let alone as proof- especially without questioning what gave me the ability to detect the ancient flying lizard's presence. What special power was I born with that enabled me to comprehend the majestically transparent dinosaur which you remain unfortunately exempt from?
If you have any sense at all you would dismiss my pterodactyl claim out of hand until I could provide sufficient evidence. The final level of desperation for most theists is the threat of hell as punishment for disbelief in the God that created us without the ability to detect or comprehend him. So I'll close with a question, for all those of you who threaten atheists with hellfire, but have the nerve to not believe the pterodactyl is on my shoulder. Would you be any further convinced if I suggested it was also responsible for creating the entire universe, will pass judgment on you for your worthiness of an eternity of torture or paradise when you die, and that you must believe in it because I happen to have a close, personal relationship with it? Answer honestly- your God doesn't like liars.