I have long been puzzled why "not" appears in constructions like:
- Do you not agree that X is a most pleasant person?
when it is clear from the context that the person asked clearly does agree that X is pleasant. If the question were "Why do you not agree....." the question would make sense, although it would be a different conversation.
I notice this construction mostly in the works of English writers, especially in those of the first half of the 20th century, although the most recent example I saw was in "Passionate Nomad, The Life of Freya Stark", by Jane Fletcher Geniesse (The Modern Library; 2001).
How and when did this construction arise? Is it part of an older style? It seems precious to me, although the biography of Freya Stark in which I found the latest example is not in the least precious.