Wouldn't it be considered as the double negative in the sentence like "I don't disagree"?
********** NOT A TEACHER **********
Ostap,
(1) As the other posters have said: Yes, it is a double negative.
(2)
But it is a GOOD double negative.
(3) Grammar books call this kind of device (use of the language)
a
LITOTES.
(4) Native speakers occasionally use litotes in order to give a
certain flavor to the language. The more you learn English, the
more you will understand when and how to use litotes.
(5) Maybe the most famous litotes is "not bad."
(a) Some books say that "Not bad" = good.
(b) But as Mr. William Safire points out in his
On Language
(New York City: Times Books, 1980):
Sometimes it means
between "good" and "bad":
Mother: How do you like my chocolate cake?
Husband: Wonderful.
Rude son: Horrible.
Kindly daughter: Not bad!
(That was only my dialogue. Not Mr. Safire's.)
(6) I found a wonderful explanation in
Webster's Online Dictionary
(definition of "double negative"):
I do not disagree:
(1) I certainly agree.
or
(2) You may be right, although I am not sure.
Mr. Jones is not incompetent:
(1) He is very competent.
or
(2) He is very competent but not brilliantly so [competent].
*****
Thank you for this interesting question. I learned a lot while
trying to answer it.
Happy New Year