Not to single out dloubet, because a lot of people have said this. I think the crux of the question is what would you say would be valid evidence?
Well, I did offer the following line: If a god, afterlife, or spiritual realm, cannot muster the same level of evidence as the chair I'm sitting in, then it has not earned my conditional agreement.
There are numerous lines of evidence all leading to the nearly inescapable conclusion that I'm sitting in a chair. Do I really have to cite one in particular? Ok, how about: My knees are bent, and I'm in a completely unbalanced position and should fall backwards, but for some reason my ass isn't on the floor. Or: I can clearly feel a soft surface underneath my ass that's holding me up off the floor. Or: I can clearly feel, see, hear, and if I so choose, smell or even taste the chair that I claim I'm sitting on.
But I say "nearly inescapable" and "conditional agreement" because I could be a brain in a box, and the chair and everything else I experience could be mere illusions. But I figure the odds of that are slim. So the things I experience daily: 99.9999... percent certain they exist.
Now, if I was presented unambiguous evidence of a god, I could never get near 99 percent because I would have to be omniscient to determine if the thing was omniscient, omnipotent, or omnibenevolent. I would be able to agree that its a powerful thing, but there's no way I could reliably identify it without being omniscient myself.
Throw in evidence for a "Father of Lies" creature, and all bets are off. Because if a supernatural being with unknown powers of persuasion existed, the very concept of knowledge itself would die a horrible death. Hell, the evidence of a god would cause the same thing. A being that can invisibly interfere with each and every observation ever made? Knowledge would be dead.