An English editor of a famous classic says in his notes to the book: "Double negatives in Elizabethan grammar amount, not to an assertion as they do in current English, but to an emphatic negation".
It is true that in Elizabethan literature, a double negatives amounts to an emphatic negation, rather than to an assertion, as the man in the street may think. Thus, "I don't want nothing" is only an emphatic form for I don’t want anything or I want nothing. This sounds quite unreasonable, but it is the fact.
What I wish to tell you is that this unreasonable fact is not peculiar to Elizabethan literature. It exists at present. Double negatives used as an emphatic assertion may be said to be found in current English, unless by current English is meant English current among educated people along.
Have you ever found such double negatives in your reading, reader? I believe you have, if you have read a modern novel or drama or short story. I do not want you to use this unreasonable construction (I want you to talk and write like an educated person). But I believe every learner of English should know it.
There are several English usages that every learner of English should know, but which many, or even most, Chinese learners do not know, because they are not to be understood by means of mere logic and are not to be found in ordinary grammars. The double negative is one of them.
NOTES
1. Double Negatives 否定
2. Elizabethan 英国女王伊丽莎白一世(1533—1603)时代的。
现在英国女王的名字也是伊丽莎白,一般称作伊丽莎白二世(1926— )
3. do=amount to
4. amount, not to..., but to... 不等于...而等于...
5. man in the street 一般人
6. sounds 听来似乎
7. peculiar to ...所独有的
8. by current English is meant English current among educated people alone 所说的当代英语就是指通行于受过教育的人们中间的英语
9. are not to be understood by means of mere logic 并非只靠逻辑就能被理解