Myth 14: "Double Negatives are Illogical" by Jenny Cheshire
The use of double negatives is a grammatical use which is very irritating to most people. They say it is illogical because when you use two negatives in a sentence, they cancel each other out, making it in fact a positive sentence. But language is not maths, so the rule double negative is positive should not be applied.
This is the reason why double negatives, are, very definitely, not illogical.