When two negatives are used in one single clause, it is called a double negative. It is usually used to emphasize the negative in a statement, and is only considered acceptable in informal language.
I can't get no sleep
I can't get no sleep
I need to sleep, although I get no sleep
I need to sleep, although I get no sleep.
- Insomnia, by Faithless
This song is a clear example of double negatives that many lyricists and musicians resort to, as a way of portraying the significance of a particular statement. Where the singer tries to explain that he can't get any sleep, and uses "can't" and "no" together, to emphasize it, the statement actually means that he can get some sleep. In another case, you could take the example of Pink Floyd's popular song - We don't need no education... Obviously the emphasis is on the fact that no education is necessary, in literal terms the line means that we do need some education. Let's try and understand what a double negative is, and then take a look at some examples to help you identify it in a statement.
As is evident, the use of double negatives is grammatically incorrect. This is because according to the rules of language, just like Mathematics, two negatives result in a positive. For instance:
If you don't got no experience, you can't be trusted with this job.
Here, the use of don't and no in the same sentence invalidate each other, and actually result in a positive answer. This means that while the sentence actually implies that if you have no experience you can't be trusted with the job, technically it means, if you have 'some' experience you can't be given the job. This sentence then cannot be considered valid as it has no logical explanation. Due to this double negation, instead of emphasizing the necessity of experience for the job, the sentence actually states that even some experience will not help in getting the job. Double negatives are mostly used in colloquial language and rarely in formal writing.
Double negatives are not only common to the English language. They are common to several other languages, but not every language considers it as incorrect. In some languages it is simply a way of speech. Here we try to identify double negatives with the help of the examples mentioned below, along with the implied meaning and the actual meaning.
1. She can't make no friends with nobody.
Implied Meaning: She can't make friends with anybody.
Literal Meaning: She can make friends with somebody.
2. I did not barely understand what you were saying.
Implied Meaning: I did not understand anything you said.
Literal Meaning: I understood everything you said.
3. I never saw nothing.
Implied Meaning: I never saw anything.
Literal Meaning: I saw something.
4. That attitude won't get you nowhere.
Implied Meaning: That attitude won't get you anywhere.
Literal Meaning: That attitude will get you somewhere.
5. I'm not going to no party.
Implied Meaning: I'm not going to any party.
Literal Meaning: I am going to a party.
6. I don't want no sympathy from you.
Implied Meaning: I don't want any sympathy from you.
Literal Meaning: I want some sympathy from you.
7. He can't hardly wait for his present to arrive.
Implied Meaning: He can hardly wait for his present to arrive.
Literal Meaning: He can wait for his present to arrive.
8. Kevin shouldn't have nothing to do with his colleague.
Kevin shouldn't have anything to do with his colleague.
Literal Meaning: Kevin should have something to do with his colleague.
9. The pilot could not find nowhere to land.
Implied Meaning: The pilot could not find a place to land.
Literal Meaning: The pilot could find some place to land.
10. I haven't had no luck with finding a job.
Implied Meaning: I haven't had any luck finding a job.
Literal Meaning: I have had some luck finding a job.
While the literal meaning of double negative has been provided above, there is an exception to the rule that is acceptable in spoken and written speech. A figure of speech known as litote may utilize two negative terms to understate a certain fact. For example, one may say:
I would not describe the minister as unintelligent.
In this case, the implied and the literal meanings of the statement are the same. So while double negatives are used to affirm a fact and technically mean the opposite of what they are supposed to mean, litotes are used to understate a fact and mean exactly what they are supposed to mean. Both however, do utilize two negative terms for the purpose. As such, a litote may be considered an acceptable form of double negative.
With the examples provided above, you can easily identify such errors by way of speech or writing. Remember that using double negatives is incorrect as per the basic rules of English grammar. While you may imply that you don't know a thing about stocks when you say 'I don't know nothing about stocks', it sounds like 'you do know something about stocks'; and you may just end up being given a job related to them!