
Home / TIL you CAN prove a negative
Today I learned the adage "you can't prove a negative" is false because you can prove a negative. It's very easy. We need to stop saying that. A better statement to use is "he who asserts a positive has the burden of proof."
Here are some of the reasons why this adage is false:

By stating that you cannot prove a negative, you are making a negative statement that, if true, contradicts your statement. In other words, it's selfrefuting.

If you cannot prove the statement, it's an arbitrary statement that has no basis and is not useful in any logical sense (i.e., it's nonsense).

There are many examples where this is not true. You can prove that 1 does not equal 0. You can prove that 2 is not greater than 3. You can prove that an equilateral triangle doesn't have any right angles. You can prove you don't have a million dollars in your pocket right now. You can prove that a flipped coin that lands on heads is not tails. You can prove that there isn't a rainbowcolored, firebreathing unicorn sitting on your shoulder. You can prove you are not reading this article while having sex on the moon. You can prove you are not dead.

To have identity is, by definition, to have a single/the same identity. Therefore, if you can't prove a negative, you also can't prove a positive. (Or, another way to say it: every claim of positive knowledge is a claim that disproves all alternatives.) This is also referred to as the Aristotle's Law of Identity (aka A is A). For example, to prove that 1 = 1 is to disprove that 1 = 0.

Related to the law of identity and another one of the three classic laws of thought, the law of noncontradiction states that "contradictory propositions are not true simultaneously." Reality conforms to the law of noncontradiction (i.e., you can't have a certain attribute and not have the same attribute at the same time). Yet the law of noncontradiction is a negative statement and relies on negation. (There are controversial theories in quantum mechanics such as the Copenhagen interpretation which imply reality violates the law of noncontradiction, but they currently remain inconclusive and people can't seem to even precisely agree on "any concise statement which defines the full Copenhagen interpretation.")

You can't reasonably test every proposition. For example, to test the proposition that there aren't any such things as rainbowcolored unicorns, you would have to check every part of the universe at the same time. The best we can do is infer using inductive reasoning to make generalizations from what we do and can know.

Science is all about proving negatives, which can be done in as few as one experiment.
People make negative statements when they are unable to provide evidence of their beliefs (e.g., "can you prove that God doesn't exist?"). So, instead of retorting that you can't prove a negative, focus on the lack of evidence to test the proposition. Focus on the reasonability of doubt. The inability to invalidate a proposition does not make it true. That's the key.
James Randi Lecture @ Caltech  Cant Prove a Negative
What did you learn today?
DISCUSS!
Original posting by Braincrave Second Life staff on Sep 27, 2011 at http://www.braincrave.com/viewblog.php?id=652
About braincrave
We all admire beauty, but the mind ultimately must be stimulated for maximum arousal. Longevity in relationships cannot occur without a meeting of the minds. And that is what Braincrave is: a dating venue where minds meet. Learn about the thoughts of your potential match on deeper topics... topics that spawn your own insights around what you think, the choices you make, and the actions you take.
We are a community of men and women who seek beauty and stimulation through our minds. We find ideas, education, and selfimprovement sexy. We think intelligence is hot. But Braincrave is more than brains and I.Q. alone. We are curious. We have common sense. We value and offer wisdom. We experiment. We have great imaginations. We devour literacy. We are intellectually honest. We support and encourage each other to be better.
You might be lonely but you aren't alone.
Sep, 2017 update: Although Braincrave resulted in two confirmed marriages, the venture didn't meet financial targets. Rather than updating our outdated code base, we've removed all previous dating profiles and retained the articles that continue to generate interest. Moving to valME.io's platform supports dating profiles (which you are welcome to post) but won't allow typical datematching functionality (e.g., location proximity, attribute similarity).
The Braincrave.com discussion group on Second Life was a twicedaily intellectual group discussions typically held at 12:00 PM SLT (PST) and 7:00 PM SLT. The discussions took place in Second Life group chat but are no longer formally scheduled or managed. The daily articles were used to encourage the discussions.
Someone's Reading
Related Posts
Latest Activity

braincrave posted "Dating online? Watch that ad!" in braincrave

Mitcheltafur commented on "An interview with David Eagleman, neuroscientist" in braincrave

braincrave posted "The solution to the war problem" in braincrave

braincrave posted "The Great Hoax of Equality" in braincrave

braincrave posted "Manipulating Americans is easy" in braincrave

braincrave posted "Irrational selfinterest" in braincrave

braincrave posted "The age of nanotechnology" in braincrave

braincrave posted "TIL reallife levitation does exist" in braincrave
 More...