For reasons that can only be understood as originating from a serious misunderstanding of the most basic principles of predicate logic, many people claim that it is somehow easier to prove a positive than a negative. It is even common to believe that proving a negative is impossible. Neither belief is true. In deductive logic, both a positive and a negative proposition are of equal difficult (or easy) to prove.

I bring this up because this is a recurring theme in all too much of our discourse. The presenting concern was comment on the question of Secretary of State Clinton running for President in 2012. But I hear this kind of nonsense from people who should know better all the time.

Calling for *proof *of a negatively or a positively stated proposition, is almost always wrong minded. The best we can do in nearly all non-mathematical contexts (and not all of those) is weigh the evidence and formally or informally develop the probability for or against the proposition. There are four computers and no elephants in this room but don’t ask me to prove either proposition. Do ask me to explain why I think the one and not the other, ask me to be crisp (or at least consistent) in my definitions and require that I offer universally available evidence so you can weigh it too. The smaller the domain of the evidence the closer one can come to something that is more of less a proof. The good thing about the stuff in this room is that the domain of the evidence is relatively small: that is not counting the junk in the closet but I don’t think there’s an elephant in there either.

# Sunday Rant On Proving A

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3 thoughts on “Sunday Rant On Proving A ~~Negative~~ Positive”

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Your computers repel elephants? Cool!

To me, asking for “proof” is usually associated with a (usually unfair) imposition of the burden of proof on the other side.

Chris,

Yes and also giraffes but I do worry about the occasional stray hippopotamus.

Stephen,

I couldn’t agree more.