Today's Atheist Fallacy: Argument From Ignorance

Ironically, it was outspoken atheist pop science TV personality Carl Sagan who said, in his book The Dragons of Eden, "absence of proof is not proof of absence." He spoke of space life. He easily handed to the mere extraterrestrial what he refused to grant to the supernatural : a reasonable probability that it was there and simply hadn't announced itself to everyone yet.
Sagan searched for answers to questions he thought all humanity had failed to frame intelligently so far: What is consciousness? Are we alone as self-aware, planning, moral beings? Is this world, or the universe, purposeful? What matters most? Why have we a desire to do more than survive and pass on our genes, even more than to acquire wealth and social standing? Why is there trans-species self-sacrifice? Who has seen what nature normally does not do -- and what really happened in these cases? Are we merely another part of nature or separate from it? What hurts when we try to live as if we had no souls, what is that emptiness, why do we find it intolerable? Is there a soul apart from the body? Where did everything and everyone and everyplace first come from? What makes a thing alive? When is a person a person?
He deserves some admiration for devoting a whole career to asking such questions, and for occasionally speaking of his own smallness and ignorance to the whole world, his audience. We should all be as willing to be small before the giant hole strewn with fire and rocks our planet spins through.
But he was no scientist. Science means always looking at the evidence and always letting it speak for itself; seeing what we want and what we don't want with the same straight-on gaze; consistent logic, equally level when applied to easy puzzles and to tough ones. He buckled when faced with what science could never address adequately. He would have been even more admirable if he had bowed before such mysteries as did Einstein, Schrodinger and Newton, and confessed that his sextet could not measure such spans, his needles spun helplessly before the gravest quests.
The argument from ignorance means putting one's worldview into the spaces between things one knows. Those who use such an argument look for spaces into which to wedge their theories. They feel surer of themselves when they deny evidence because less proven is less of their opinion crowded out of the puzzle.
Proof of absence is more than absence of proof.
It is impossible to prove a universal negative.
If I said there are zebras in my room, you could, if you were in my room, search for them. On finding no zebras and no room for zebras you could announce that it was false -- you had proof of absence of zebras in my room.
However, if I said there were zebra-unicorns, you could search the whole world, and even if you turned up no evidence of zebra-unicorns, it wouldn't prove there were none. One could have been born while you were searching elsewhere. There could be some hidden in a place that formed after you left the area. You might just have kept missing them. Even if there were none on earth, there could be some elsewhere.
If I could bring you one zebra-unicorn, and you could examine her and see that her horn was real and hers, a zebra-unicorn's existence would be established. But the absence of any would never be able to become solid knowledge.
Sagan didn't believe in God. He said everything anyone ascribes to God could be credited to some other origin. He had no proof of God. He violated Occam's Razor by ultimately multiplying factors prolifically to get rid of the need to include the supernatural. Many atheists do the same thing.
Here's a hypothetical example: A woman with a known, documented tumor in her ear goes to a faith healer and it vanishes. Her doctor confirms that it is gone. She announces the miracle. An atheist steps in to say the healer was merely a hypnotist using the suggestibility of crowds to make her feel healed. He posits that her doctor was getting a bribe to falsify the records. He says even if she never paid the healer and even if she was actually penniless, her family must have bought the phony miracle. Even if shown that she has no religious relations, the atheist will say she has been paid secretly by some organization. The lack of evidence of such will just be dismissed. He will fold his arms tightly, stick his lower lip out, squint, shake his head slowly and say, "You never proved to me that she even had a tumor. It's a blob on a piece of X-Ray film. Lots of doctors are wrong all the time." If you take him to the healer and his own broken toe is healed as he enters the room, he will say there is no proof it wasn't a coincidence. Plenty of bones heal after a delay. Granted it was a fantastically improbable coincidence that it would heal at that moment, but he will not accept any supernatural explanation. He will point to miracle after miracle and state in serious tones that in one room at one moment twenty people had mass hysteria, including several who came in skeptical, and had also somehow bribed or brainwashed their own doctors and medical staff all by sheer happenstance, ten were just ready to heal by coincidence at the same hour, five had been in mass hysteria despite no contact with or awareness of each other over a period of many years, and four are pathological liars, all just happening to come up with identical lies at the same time despite having nothing to gain but a moment's attention, and laying out travel expenses. He will posit sheer conjectures of mental processes that might exist, all to explain away part of what he sees here, part there, piecemeal until he cannot piece any more pieces and then he will say there are "lots of things that could be happening here," suggest vaporously that someone is irrational and something is all explained somewhere, refuse to explain anything further and walk away hugging himself. After deciding the evidence isn't evidence to him, he is likely to announce that "so far no one has been able to prove anything" supernatural and then he will say it is irrational to believe in the supernatural, for it has never been proved. Thus, he suggests, it has been proven not to be.
This Gordian Knot is a defense mechanism against recognizing his mental helplessness in the face of something -- indeed most likely Someone -- all his knowledge can't come close to comprehending. It would humble him far too much. Emotionally, he might not be ready.
Respond with reason and let him walk away if he gets too upset. He will wonder and one day, if he is intellectually honest, he will ask again, and perhaps let the facts speak.
Even if the atheist will not acknowledge proof, at least he must finally admit that absence of proof is not proof of absence, a universal negative canot be proven and the argument from ignorance is just an ignorant way to argue.