Quote Originally Posted by Throbert McGee View Post
A teacher is explaining to the class that a double negative creates a positive meaning, and gives the example that "I haven't never eaten sushi" actually means "I have eaten sushi before."
Is it true that a double negation in English creates a positive meaning? As far as I know, double negation is used sometimes in colloquial English, and it has a negative meaning, not positive (The phrase ‘I haven’t never eaten sushi’ means ‘I have never eaten sushi’ and shouldn’t be understood as ‘I have eaten sushi before’, should it?).

Or the teacher uses an unfair method of proofing the superiority of the literary language over a substandard one, trying to apply mathematical logics to language?