[Harmless Teddy Bear]

An example would be the use of a double negative (I can’t get no satisfaction). It makes complete grammatical sense, as an intensifier.

Bull. A double negative is a positive. The second negative is a modifier which turns the first negative into a affirmative. Or to state the math rule, "minus a minus is always a plus".

So the speaker is stating that he does get satisfaction.

[SeekAndFind]

Is the word “Ain’t” still proper English?

[JRandomFreeper]

Language is NOT mathematical. People forget that to their own undoing.

/johnny

[teacherwoes]

Or to state the math rule, "minus a minus is always a plus".

That was before Common Core came along. Who knows if it's true or not now.

[KarlInOhio]

Most varieties of early English used double (Chaucer even reached a quadruple once) negatives as intensifiers. The English around London which became standard had the quirk of not allowing double negatives. That being said, descriptivist linguists can dispassionately investigate and write papers about the origins of that rule at the same time prescriptivist teachers can teach people that in modern English double negatives aren't used and get out the big red pen when students them.

Also, aren't those who state that all linguists must be descriptivists themselves prescriptivist on that issue?

[Oztrich Boy]

And if riting used the rules as rithmetic, you would be correct

[dr_lew]

It's called "negative concord" cf. Wikipeida Double negative

"Ther nas no man no wher so vertuous" ("There never was no man nowhere so virtuous"). - Chaucer

... and if Chaucer ain't English, I don't know what!