Thursday, August 22, 2013

Tablet Thoughts: Burden of Proof


I came across a book purporting to teach logic to youth in a fantasy story. Skimming through the pages, I came across the following assertion: You can't prove a negative. The person making the positive statement has the burden of proof.

The sound you hear is me pounding my head against the wall. This kind of claim could,  if allowed, let a person say anything he wants in a negative form and the person who finds it ridiculous is suddenly the one who has to disprove it.

Why the Claim is False

So if a Klansman says "Blacks are not intelligent," we're supposed to believe that the burden of proof is on the member of the NAACP who believes they are?

No, the burden of proof doesn't fall to the person who makes the positive assertion. Nor does it fall on the one who makes "the more extraordinary claim" (a popular tactic by atheists who claim God doesn't exist and then demands to be disproved).

Shifting the Burden of Proof

In logic we call this shifting the burden of proof, making a claim and instead of proving it, demanding the argument be disproved.

The problem is, the burden of proof must be met by the person making the claim. If I say, life on other planets exists, I have the obligation to prove my claim. If I say, life doesn't exist on other planets, I also have the obligation to prove my claim.

What this means is the person who wants to make an assertion needs to realize that if they want it to be seen as anything more than a personal opinion, they need to be able to establish reasoning that justifies their view.

The Danger of Negativity

So, if you make a negative claim, you do have to prove it. That can be a real problem with the larger claims.This is because if you say "no X is part of Y" you have to know everything about Y to know that there is no X that is a part of it. On the other hand, if you claim X is part of Y, all you have to do is  know the part of Y that X is part of.

So if I said, there is a dog in the living room, the only part of the living room I would have to know is the part the dog was occupying (Dammit Annabelle, stop walking around in circles and go to sleep).

But, if I should say there is no dog in the living room, I would need to know about every part of the living room to know she wasn't hiding behind the couch or under the table or standing in the corner whimpering because she thinks she's trapped (she's going senile, sadly).

And that's just a dog in a living room. Now consider the assertion "God does not exist." That assertion says that there is no God in all of existence. This means to know God does not exist, I have to know about every part of existence.

Good luck proving that.


The thing to remember is we do not have to let people get away with making negative attacks and then demand we disprove them. The one who asserts a thing has the burden of proof.

Once both sides recognize that, we can actually have meaningful discussions about what is true and false.

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