The use of two negatives in a sentence is much more common than is generally supposed. To assume that only those who are grossly ignorant of grammatical rules and constructions employ them, is an error. Writers whose names are as bright stars in the constellation of literature have slipped on this treacherous ground.
A negation, in English, admits of only one negative word. The use of a single negative carries the meaning halfway around the circle. The meaning is therefore diametrically opposed to that which would be expressed without the negative. The use of a second negative would carry the meaning the remaining distance around the circle, thus bringing it to the starting point, and making it equivalent to the affirmative. The second negative destroys the effect of the first. The two negatives are equivalent to an affirmative.
Double Negatives
While two negatives in the same sentence destroy each other, a double negative has the effect of a more exact and guarded affirmative; as, "It is not improbable that Congress will convene in special session before the end of the summer." "It is not unimportant that, he attend to the matter at once." "His story was not incredible." "The fund was not inexhaustible."
Redundant Negatives
"No one else but the workmen had any business at the meeting." Omit else.
"Let us see whether or not there was not a mistake in the record." Omit either or not or the second not.
"The boat will not stop only when the signal flag is raised." Omit not or change only to except.
"He will never return, I don't believe." Say, "He will never return," or, if that statement is two emphatic, say, "I don't believe he will ever return."
Don't want none
"I don't want none," "I ain't got nothing," "He can't do no more," are inelegant expressions that convey a meaning opposed to that intended.
"I don't want any," or, "I do not want any," or, "I want none," are correct equivalents for the first sentence; "I haven't anything," or, "I have nothing," should take the place of the second; and, "He can't do any more," or, "He can do no more," or "He cannot do more," will serve for the third.
Not--Hardly
"I cannot stop to tell you hardly any of the adventures that befell Theseus." Change cannot to can. "I have not had a moment's time to read hardly since I left school." Say, "I have hardly a moment's time," etc.
No--no
"The faculties are called into no exercise by doing a thing merely because others do it, no more than by believing a thing only because others believe it," says George P. Marsh. He should have used any instead of the second no.
Nothing--nor
"There was nothing at the Columbian Exposition more beautiful, nor more suggestive of the progress of American art, than Tiffany's display." Change nor to or.
Can't do nothing
"He says he can't do nothing for me." Use "He can do nothing," or "He can't do anything for me."
Cannot by no means
This double negative should be avoided. "I cannot by no means permit you to go." Say, "I cannot possibly," or "I cannot, under any consideration, permit you to go."
Nor--no
"Give not me counsel, nor let no comforter delight mine ear," says Shakespeare.
"There can be no rules laid down, nor no manner recommended," says Sheridan.
"No skill could obviate, nor no remedy dispel the terrible infection."
The foregoing sentences may be corrected by changing nor to and.
Not--no
"I pray you bear with me; I cannot go no further," says Shakespeare. "I can go no further," or "I cannot go any further," will make the sentence correct.
Nor--not
"I never did repent for doing good, nor shall not now."
"We need not, nor do not, confine the purposes of God."
"Which do not continue, nor are not binding."
"For my part I love him not, nor hate him not."
In these sentences, change nor to and.