"Absence of evidence is not evidence of absence".

[Angrboda]

Well of course you can't "tell the difference" between an undetectable god and a non-existent god. If you could, that would make him detectable.

If you don't have a way to detect something, believing in it is irrational.

Dark energy.

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The saying is correct. It's also frequently misinterpreted. Perhaps it would be clearer to say, "Absence of evidence, by itself, is not evidence of absence."

What else do you need apart from evidence?

I'm with Min on this. Just because some man said absence of evidence is not evidence of absence does not make it true or even remotely so. The way some people use that phrase to try and end an argument in their favour, you'd think it was a universal law or something.

What I said and what Min said do not contradict each other.

If I believe there is a starving cat in my neighbor's house, and I go look for it and don't find it, my search results are evidence of the absence of a cat. However if I just sit in my own house and ponder whether or not the cat exists, prior to looking for it, my absence of evidence in that case is not evidence of absence. And in the more general case, the amount that absence counts as evidence depends on the probability, given it exists, that the lack of evidence in observations conducted so far could occur. Needless to say, that calculation can be highly subjective.

But an absence of evidence, in and of itself, is evidence of nothing. Imagine the opposite case. Do you have evidence of a blonde haired, blue-eyed Chinaman named Wong living in Shanghai? Is that evidence he doesn't exist? Do all the things you haven't personally examined therefore have evidence against their existence because of your ignorance?