Are double negatives actually wrong?

In standard written English, double negatives are treated as errors, and the usual justification is that two negatives cancel to a positive, so I don't know nothing supposedly means I know something. That argument borrows from mathematics and does not describe how language works. Negative concord, where multiple negative elements reinforce a single negation, is the normal system in Spanish, French, Russian, and many other languages, and it was standard in English through Chaucer and Shakespeare, who used it freely. It remains systematic and rule-governed in African American English and numerous regional dialects, where speakers apply it consistently rather than randomly.

The prohibition entered English through 18th-century prescriptive grammarians who explicitly imported logical and Latin-derived reasoning to legislate usage, and it stuck because standardized education enforced it for two centuries. So the accurate framing is that avoiding double negatives is a convention of a prestige dialect, and violating it carries real social and professional consequences, which is a genuine reason to follow it in formal writing. But calling it illogical or a sign of careless thinking is linguistically unfounded, and it is worth separating the practical advice, use standard forms where you are being judged by them, from the false claim that the dialects using negative concord are broken versions of English rather than coherent systems with different rules.