Appeal to ignorance

"A lot of people might say, "Well, you can't prove metaphysical idealism is false, can you?". (These are the sort of people who think The Matrix has deep philosophical significance.) Arguments like that are pretty lame, though; they commit the fallacy of appeal to ignorance. You appeal to ignorance when your only premise in support of a claim is that you or your opponent can't show the claim is false, i.e., you are ignorant of any evidence that would disprove it. But that kind of ignorance doesn't prove anything. Think about it: I can't prove the universe didn't come into existence five minutes ago, complete with "historical" records and "memories," but the fact that I can't prove it's false doesn't make it true, or even plausible. I can't prove there isn't an invisible elephant (with no odor or any sensible properties) in my backyard. But if I seriously concluded on the basis of my ignorance of reasons for disproof that there were such an elephant, you would not say "Ms. LaFave, you are such a deep thinker"; you would say "Ms. LaFave, you are out of your mind". "