← Back to archive

"You can't prove a negative"

Historical archive only. New interaction is disabled.

Original Question
It's reported that a politician who's a notable right-winger threatened to nuke another country years ago. However, there isn't enough evidence to substantiate the claim.

One of his supporters says, "You can't prove he said that."

I counter, "You can't prove he did NOT say that. Moreover, he has threatened to nuke other countries. Therefore, this rumor can't be proved or disproved, but I consider it believable."

The supporter then says "You can't prove a negative."

Is this a fallacy or just some kind of obfuscation or diversion? I'm not even sure what a "negative" is.

Answers

2
Hmm.

It is often possible to prove a negative, although sometimes it's difficult.

But we have the concept of burden of proof. If you say that the guy threatened to nuke someone, it is your job to prove it. This time, I think the fallacy is on you.
Within the English language, it is grammatically correct to use a "double negative", It's called the rule of double negation.

Consider this, is "you cannot do something" provable?
E.g. You cannot jump off the international space station at its current location and land on Pluto.
If "you cannot prove a negative" is true, then you've just proven "you cannot do something"....You cannot prove a negative is itself a negative. The statement is a self-contradiction.
Link to an explanation....
https://departments.bloomu.edu/philosophy/pages/content/hales/articlepdf/proveanegative.pdf
Book

Want the full book?

Get the complete guide to logical fallacies by Bo Bennett.

Buy the Book

Master Logical Fallacies Online

Take the Virversity course and sharpen your reasoning skills with structured lessons.

View Online Course