Welcome to Logical Fallacies 101, an ongoing exercise to help foster more reasonable debate on Newsvine and wherever else you may find yourself discussing differences of opinion.
So far, we've covered the ad hominem and association fallacies. I'm breaking these down one at a time, and trying to make them fun and simple. Logic can be pretty obtuse, so hopefully treating them in small chunks will make the ideas accessible to everyone. To remind you of the basic definition I'm running with:
A fallacy is a rhetorical sequence that doesn't logically connect. For a variety of reasons, logical fallacies are invalid. A logical fallacy does not necessarily render the point invalid, but it means you need to rethink how you're making your point.
Today, we dip into a commonly cited -- and commonly mis-stated -- fallacy: the argument from ignorance.
Now, might snarkily be saying that any argument you disagree with is from ignorance. Har! But the argument from ignorance is actually quite a bit different. First, let's cover what it isn't. You've probably heard this at some point:
You can't prove a negative!
Sure you can! If you wanted to argue that I don't have a million dollars in my primary bank account, you could easily prove it. Find a bank statement, and bam, you just proved a negative. You proved that something isn't true. But you're on the right track to cite the argument from ignorance.
(Don't worry if you've seen or said "you can't prove a negative." Everyone's done it sometime, myself included.)
An "argument from ignorance" states that if something can't be disproven, it is therefore proven. It's a false dichotomy, claiming that only two possibilities exist. If something can't be disproven, it doesn't necessarily mean it is proven, hence the fallacy.
When you state it outright that way, it sounds pretty obvious, but this happens more often than you might think. Let's take a look at a simplified example to get our bearings:
Statement: Show me the proof that unicorns don't exist!
Most often this is used as a defensive argument, rather than an offensive one. That is to say, when someone cannot prove their point, they retreat to the argument from ignorance to challenge their opponent to disprove the point. Because of this, it goes hand-in-hand with burden of proof. I'll get into burden of proof in more detail at a future date, but for now, suffice it to say that this is when it crosses the line into fallacious territory. A person should prove their own statement, rather than relying on the inability to disprove it. In the above example, the debater should show some evidence of unicorns' existence, rather than the inverse.
When used as an offensive argument, it is often used to imply without making a definitive statement. Someone may not directly accuse anyone of wrong-doing, instead opting to imply wrong-doing and then rely on their opponent's inability to disprove it.
One public example of an offensive implication is the recent hoax that Glenn Beck raped and murdered a girl in 1990. Yes, I'm aware that the hoax was meant to satirize Beck's own frequent use of the argument from ignorance. But also serves as a great example of the argument from ignorance. It uses a degree of specificity (specific crimes, a year) to sound believable. But then it challenges Beck to disprove the claim. Of course, he can't. He can't show proof of what he did every moment of every day for an entire year. And so, the argument from igorance "wins."
Except it doesn't win. The argument from ignorance is a fallacy, and next time you see someone committing it, you can call them on it.