Isn’t this sentence a case of double negative?

Question

Isn’t this sentence a case of double negative?

No, failing at something doesn’t mean you can’t be happy.

What are some other cases where double negatives may work or where they may not actually be double negatives in the first place?

Answer 1

English has no rule against ‘double negatives’ per se.

No, that is not a case of the forbidden kind of “double negatives”, since your negatives are in two different clauses. That is not a strange thing at all. Does not mean is in one clause and you cannot be happy is in another. That’s perfectly sensible.

But English doesn’t have rules against double negatives anyway. Double negatives can be quite useful. You must be thinking of the admonition against negative concord in Standard English, which is something else altogether. From the Yale Grammatical Diversity Project:

Negative concord refers to the phenomenon in which more than one negative element occurs in a clause but the clause is interpreted as having a single instance of negation. [...] Negative Concord is a widespread phenomenon in non-standard varieties of English.

John Lawler likes to cite Horn’s Law:

Horn’s rule is Simplex Negatio Negat; Duplex Negatio Affirmat; Triplex Negatio Confundit. Single negative negates; double negative affirms; triple negative confuses.

In other words, using two negatives is perfectly sensible when one negative is used to negate another:

1. Remember not to mention the War. [Simple Negation negates.]
2. I didn’t not mention the War. [Double Negation affirms.]
3. I didn’t remember not to not mention the War. [Triple Negation confuses.]

Many other languages use negative concord in their standard versions. With negative concord, multiple negative-polarity items in a sentence reinforce the negation — they do not cancel it out as they would in Standard English.

From the Yale site we see these examples:

• I ain’t never been drunk.
• Nobody ain’t doin’ nothin’ wrong.
• I don’t never have no problems.

Those all occur in non-standard versions of English. Once upon a time English did use negative concord in the standard language, but no longer.

Other languages like Spanish (amongst many others) continue to employ negative concord. Here’s an example of four negatives in the original, along with a literal and a “proper” translation:

• Spanish: No tengo nada que decir a nadie nunca.
• Literally: I don’t have nothing to say to nobody never. [non-standard]
• “Correctly”: I have nothing to say to anybody ever.

Note that words like any and ever are negative-polarity items in English, but they do not count as actual negatives for purposes of the admonition against using multiple negatives for reinforcement. Instead, these negative-polarity items are a form of negative concord using non-negative words.

Answer 2

In the sentence provided as the example in the question there is no double negative. Double negative is called the situation when one negative negates another one. For instance, The answer isn't not correct. The fact that several verbs in the sentence occur with their negative forms does not create the case of double negative.

As Paul Rowe commented both negatives modify the same thing (word/phrase/clause).