非也：否定之否定=肯定； Double Negatives:

 

A double negative is the nonstandard usage of two negatives used in the same sentence so that they cancel each other and create a positive. In Shakespeare's day, double negatives were considered emphatic, but today, they are considered grammar mistakes.

Remembering that two negatives form a positive will help you to avoid the "double negative" grammar problem:

Negative + Negative = Positive Negative + Positive = Negative

Negative Words

The following list contains words that are regarded as negative. If you use them in your sentences once, your statements will be negative.

no not none nothing nowhere neither

nobody no one hardly scarcely barely

 

http://leo.stcloudstate.edu/grammar/doubneg.html

 

A double negative occurs when two forms of negation are used in the same sentence. 

http://en.wikipedia.org/wiki/Double_negative

 

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