At the surface level they can appear as binaries, but the negation of A is not equivalent to B and vice versa (e.g. illegal is not equivalent to not-legal) and encourages the consideration of more complex meta-concepts which at surface level seem like contradictions but are not (both beautiful and ugly, neither for or against).
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Others have pointed out that English speakers do have the capacity, and do use these sort of double negatives that allow for this ambiguity and nuance, but if you are an English-only speaker, I do believe that there are concepts that are thick with meaning and the meaning cannot accurately be communicated through a translation - they come with a lot of contextual baggage where the meaning can not be communicated in words alone.
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As a New Zealander who's lived in the U.S. for the last 15 years, I've realized in conversations with some native Americans where despite sincere (I think) efforts on both sides, I've not been able to communicate what I mean. I don't think it's anything to do with intelligence, but like author hints how language shapes how we think and therefore our realities.
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I've never found poetry to be interesting, but recently I've come to appreciate how I think poets attempt to bypass this flaw of language, and how good poets sometimes seem to succeed!