Looking over my book, I see a connection between two lines of reasoning that had been separate. They both have to do with situations where someone is professing both ignorance and knowledge about the same proposition. They want us to believe that they know, even though they confessedly don’t know.
The first line of reasoning has to do with the goodness of God. We are told, on the one hand, that no mere mortal knows the reason behind any act of God (he “works in mysterious ways”). On the other hand, we are told that God is perfectly good. But if you don’t know why God does things, then you don’t know that he does them for good reasons. You can’t be ignorant of his motivations, yet knowledgeable about his intentions. If you can’t explain why God does anything, how do you know he’s not perfectly evil, and trying to make us all miserable?
The second line of reasoning is about miracles. No one will claim to know how God performs the miracles he performs – yet many people claim to be certain that it was God who performed them. But if you don’t know how God did a certain thing, you don’t know that he did that thing.
Imagine that Alice goes to the police and accuses Bob of murdering Carol. They ask Alice, “How did he do it?” She replies, “I have no idea how he did it, but I’m certain that he did do it.” This would not (I hope) be regarded this as a promising lead.
(Note that to make this example more like a “miracle” story, we would have to stipulate that no one knows for sure that the putative victim, Carol, was even a real person.)
This unwarranted hop from “there’s no way to know” to “we know” is a special feature of religious “arguments.” It is unwarranted because “we don’t know P” does not imply “we know Q” for any P or Q. If you don’t know, then you don’t know.