Ain't Got No Double Negatives

Got to thinking about double negatives in English, because I'm weird and thinking about abstract linguistic concepts is one thing I do for fun.

I knew from studying Romance languages and Japanese that there are plenty of languages like these in which double negatives are grammatical, and got to wondering why we ain't got no double negatives in English too (neither?). Turns out we used to have them, but then they disappeared. The reason was a concerted effort on the part of British grammarians to impose the mathematical rule of double negatives resulting in a positive on grammar.

Not being a "math guy," this got me wondering about negative numbers in general. Apparently, ("apparently" meaning of course "according to Wikipedia") negative numbers have been used historically almost exclusively for debt and arbitrary scales like temperature, and have also been known as "absurd" or "nonsensical" numbers.

With debt, there is never really negative money, only two positive totals, one of money you have and one of money you owe. "Negative" temperatures are only temperatures below some arbitrary temperature and not the opposite of heat, hence absolute zero. So, suffice it to say that negative numbers aren't really "real" to begin with.

Take the phrase "I have no idea." It would be grammatically incorrect in English to write this as "I don't have no idea." But why? This is exactly how they write it in Spanish, French, Japanese and plenty of other languages. So is it really wrong, logically?

Look at the subject and verb, "I have" -- I exist, and the action of having is taking place, in other words I am having something. But the thing that I am having, "no idea," doesn't exist, so how can I have it? I don't think I can. If the thing doesn't exist, then by definition I can't have it. So does this then make the double negative correct?

I think the answer is "kind of." If something doesn't exist, then you can't have it -- two negatives, logical. And not having something that doesn't exist doesn't make it appear somewhere -- in other words a double negative isn't a positive.

But what we are really trying to say in the sentence is where the point lies.

If someone asked you about something, and you didn't have a good response, you might say "I have no idea." What you're saying of course is "There may or may not be a good answer to your question, I just don't have it," or, more simply, "I don't have any idea." Again, the idea may or may not exist, you just don't have it.

So, while "I don't have no idea" is preferable to "I have no idea," and hence used correctly in other languages, they both miss the point. The first says nothing happens to something that doesn't exist. Fair enough, but you're not communicating anything. The second says you have something that doesn't exist, which makes just doesn't make sense.

So why are there three different ways to say the same thing in English and other languages -- "I have no idea," "I don't have no idea," and "I don't have any idea." -- yet only one of them is logical? Because we all know what they mean and that's all that counts. But it's fun to think about, for me anyway :)