4.6: Suspending Belief

When it comes to improbable claims, the first principle is that the burden of proof in producing the good evidence is on the shoulders of whoever makes the claim or adopts the belief. If you decide to adopt a belief, you should have found enough evidence to justify your doing so. It is not good enough to say, "Well, it's never been proved false, so I believe it." Without the evidence, you should suspend your belief. That is, if you are in a situation in which somebody makes an improbable claim but doesn't supply good evidence to back it up, don't believe it until somebody gives you enough evidence or until you get it for yourself. Don't believe it even if you might like to believe it. I'd like to believe that my sweet Aunt Emma is telling me the truth when she introduces her new friends as aliens from beyond our galaxy, but rationally I should not believe her until they show me some ID.

Just kidding. If someone says, “I saw a green alien from outer space,” you properly should ask for some proof. If the person responds with, “Prove I didn’t,” then they are not accepting their burden of proof and are improperly trying to place it on your shoulders. This kind of error in reasoning is called the “fallacy of misplaced burden of proof.”

Exercise \(\PageIndex{1}\)

Here are three reports from a friend of yours, Ramone let’s say. All are bizarre, but some are more improbable than others. Which report is the most improbable, and why? The focus of these questions is not on whether Ramone is being truthful but on whether what he says is actually true.

1. I saw my uncle die because he threw salt on the ground. He did it when he and I were camping. My grandmother told us never to throw salt away or else something bad would happen soon. The very next day after the camping trip he was hit by that truck on the freeway.
2. Hey, you won't believe this. Less than ten minutes ago, I saw Mary, the one who moved away to Germany last year. Remember she went to be a gymnastics coach in Berlin? Well, she was running into the grocery store as I drove past on the freeway. She's changed a lot. She looks ten years older, and she has a plastic, prosthetic leg.
3. I swear it's true. The president of the United States called at 3 a.m. this morning. He asked me to join the Defense Intelligence Agency and spy on Bulgarian businessmen visiting Toronto. What a surprise; I’ve never done any spying in my life, and I don't even know where Bulgaria is. I'm just a shoe salesman, but today is my special day. My brother Bill was home when he called. Ask him.

Answer

Answer (a) is the strangest. Although all three stories are unusual, the spy story and the plastic leg story are not as unusual as the salt story because the salt story violates our basic understanding about what can cause what in the world; the spy story and the plastic leg story are merely about unusual human actions. Answer (a) is unlikely because our background knowledge about what causes death tells us that throwing salt isn't the kind of thing that will easily hurt anybody. Regarding (b), Ramone probably didn't get a very good look at Mary if he was zipping by on the freeway and Mary was running, but this event is not as impossible as a death caused by salt thrown down on the ground the day before. Mary's return from Germany would not be that big of a deal; people do change their plans. Losing her leg could have caused her to lose the gymnastics coaching job. The remark about Mary running with a plastic leg is odd. Answer (c) is probably an unreliable report, too. If spy agencies want someone to spy for them, they don't usually call on the phone, they don't give the candidate a specific assignment without first making sure he (or she) can keep his mouth shut, and they don't have the president make the call. So this whole story is very unusual. Ramone is joking, or he takes you for a fool. His brother is probably in on the joke, or else he is naive