Fallacy: Shifting the Burden of Proof

Scully: Your sister was abducted by aliens? Mulder, that's ridiculous!
Mulder: Well, until you can prove it didn't happen, you'll just have to accept it as true.
The truth may be out there, but who has the job of producing it in an argument? In the section on "Validity, Truth, and Soundness," we discuss the concept of a burden of proof, which is defined there as "how much each side of a dispute needs to prove in order to win someone's agreement." Sometimes, however, whoever is carrying the heavier burden attempts to shift that onus onto the other side--as Mulder does above. In claiming that his sister was abducted by aliens, he carries a much greater burden of proof, because we normally consider alien-abduction stories as incredible; as a result, it is up to Mulder to produce proof of his claim. But in the dialogue above, he shifts that burden to Scully, creating the fallacious impression that, if Scully can't prove it false, Mulder's alien-abduction story must be true. On the contrary, since Mulder is making an incredible claim, it is up to him to support it.
In easily verifiable claims, the person initiating the claim normally assumes the burden of proof. Not doing so, however, should probably not be considered a fallacy. The fallacy occurs whenever someone shifts the burden of proof to avoid the difficulty of substantiating a claim which would be very difficult to support.

Exercises:

1. Which of the following is an example of the fallacy of shifting the burden of proof?

Prosecutor to jury: "She must be guilty. After all, she has no alibi for the night of the crime."

Motorist to police officer: "What do you mean, I was doing 90 mph? Prove it!"

One lost hiker to another: "I'm going to continue in this direction, unless you can give me a good reason not to."

Tobacco company CEO to Congress: "I don't believe smoking causes cancer, because no one has ever seen it happen."

2. Choose the best way to challenge someone who says, "Gun control is a liberal plot to weaken the moral fibre of the United States! And no one has ever proved otherwise."

No one has ever tried to prove otherwise.

No one needs to prove otherwise.

Surely someone has proved this was false.

Anyone who did prove this was false has probably been shot!

1. Which of the following is an example of the fallacy of shifting the burden of proof?

You answered:

Prosecutor to jury: "She must be guilty. After all, she has no alibi for the night of the crime."

Correct!

An alibi would be support for the defendant's not-guilty plea, but that's not the issue, since the defendant is assumed to be innocent until the prosecutor proves otherwise. Instead, the prosecutor is attempting to shift the burden of proof here, suggesting that the defendant must prove her innocence or be found guilty.

1. Which of the following is an example of the fallacy of shifting the burden of proof?

You answered:

Motorist to police officer: "What do you mean, I was doing 90 mph? Prove it!"

The motorist is entirely justified in demanding proof. Not only is the cop initiating the claim of speeding, but the motorist should be considered innocence until proven guilty--and both of those situations shift the burden of proof onto the police officer. Of course, there's probably a radar gun involved, but critical thinkers shouldn't be doing 90, anyway.

1. Which of the following is an example of the fallacy of shifting the burden of proof?

You answered:

One lost hiker to another: "I'm going to continue in this direction, unless you can give me a good reason not to."

Just asking for an opponent to support his or her position is not a fallacious shifting of the burden of proof. And the speaker here is not trying to be persuasive. But what if the hiker said, "This is the right direction. Prove it isn't"? Depending on the situation, that might well be an attempt to shift the burden of proof.

1. Which of the following is an example of the fallacy of shifting the burden of proof?

You answered:

Tobacco company CEO to Congress: "I don't believe smoking causes cancer, because no one has ever seen it happen."

It's true that no one has ever seen smoking cause cancer, and it's probably true that no one ever will. In assuming that the only way to prove A causes B is to observe A causing B, the CEO warps the argument into a misunderstanding--in which the two sides refer to different things by the same terms--but this is not an example of shifting the burden of proof, which would have been the case had the CEO said, "It's God's will that we smoke ciagrettes. Can you prove otherwise?"

2. Choose the best way to challenge someone who says, "Gun control is a liberal plot to weaken the moral fibre of the United States! And no one has ever proved otherwise." You answered:

No one has ever tried to prove otherwise.

Considering whether someone has tried to prove otherwise misses the point. The best way to challenge a fallacious shifting of the burden of proof is to require the person to shoulder the proper burden. In this case, the challenge should be to require evidence of this "liberal plot" weakening the "moral fibre" or the country. If there is no reasonable support for such a claim, it should be ignored.

2. Choose the best way to challenge someone who says, "Gun control is a liberal plot to weaken the moral fibre of the United States! And no one has ever proved otherwise." You answered:

No one needs to prove otherwise.

Correct!

Of course, proving otherwise would be nice. But given the claim, that might be impossible to do. The best way to challenge a fallacious shifting of the burden of proof is to require the person to shoulder the proper burden. In this case, the challenge should be to require evidence of this "liberal plot" weakening the "moral fibre" of the country.

2. Choose the best way to challenge someone who says, "Gun control is a liberal plot to weaken the moral fibre of the United States! And no one has ever proved otherwise." You answered:

Surely someone has proved this was false.

The best way to challenge a fallacious shifting of the burden of proof is to require the person to shoulder the proper burden. In this case, the challenge should be to require evidence of this "liberal plot" weakening the "moral fibre" of the country. Worrying about whether someone has proved it false misses the point: it's up to the person making this claim to support it; otherwise, it should be ignored.

2. Choose the best way to challenge someone who says, "Gun control is a liberal plot to weaken the moral fibre of the United States! And no one has ever proved otherwise." You answered:

Anyone who did prove this was false has probably been shot!

The best way to challenge a fallacious shifting of the burden of proof is to require the person to shoulder the proper burden. In this case, the challenge should be to require evidence of this "liberal plot" weakening the "moral fibre" of the country.

Congratulations

You have finished the section on the fallacy of shifting the burden of truth.