Aristotle is very very disappointed with your logic, my friend. http://en.wikipedia.org/wiki/Inference#Examples_of_deductive...

I think you've misunderstood his post (or I've misunderstood yours (my friend))). He was saying that the linked website was illogical in using a method to distinguish humans from machines, that most humans would fail at. Grandparent wasn't attempting to construct his own logical argument.

But the logic of the CAPTCHA is "if you get this right, then you are human". Makmanalp was suggesting "if you get this wrong, you are not human", which does not follow logically from the CAPTCHA rule.

It is an example of "Denying the antecedent", or the inverse error: http://en.wikipedia.org/wiki/Denying_the_antecedent

Who is to say that "if you get this right, then you are human" is the valid premise? I'd argue that the correct one is "If you're human, you get CAPTCHAs right". :P

Just to be pedantic: CAPTCHAs are a test for being human so human-ness has to be the consequence of some condition. Your premise is therefore an incorrect framing of the CAPTCHA test.

(IsaacL, I think we are all having our tongue in our cheek here).

Well, to be fair the easiest captcha's are easy high school level equations and (as someone else already pointed out) if you can't solve these you have no business obtaining an account for extremely high quality quantum random numbers. (I believe they provide about 7.8 or 7.9 bits of entropy per byte)

I buy my random numbers from a guy in the alley behind my building. He says they fell off a truck.

I'll stick with Lavarand, thanks... good enough for my needs.

http://en.wikipedia.org/wiki/Lavarand

OMG! "extremely high quality quantum random numbers"

Thats an interesting product to sell.

It's just a little more targeted than the average captcha. It should weed out both bots and people you wouldn't want using the website in the first place.