It is an established rule of English grammar that two negatives cancel each other out.
In other words, the proper meaning of “he did not do nothing” is “he did something”.
As with all rules, there are exceptions. It is accepted that in some cases negatives can be multiplied to give added emphasis. However examples of this are few and far between, and are mainly found in literary texts, which perhaps explains why the two main authorities on English grammar, Sir Ernest Gowers ( The Complete Plain Words) and H.W. Fowler ( A Dictionary of Modern English Usage) both use the same quotation from Shakespeare’s Hamlet to illustrate this.
We can therefore safely consider that in business and legal writing, the use of a double negative would be interpreted as a mistake or lapse of style.
Below are two examples of incorrect usage by politicians, quoted by Gowers:
- There is