Negation in 未然形 + む(ん)


This question has been inspired by [this
Q&A](https://japanese.stackexchange.com/questions/93422/what-form-is-being-
used-in-%E5%8F%82%E3%82%89%E3%81%9B%E3%82%93%E3%81%A8%E3%81%A6#93429), from
which I learned about 未然形 + む(ん)'s various functions. I noticed two lines on
[the reference page @naruto points to](https://www.hello-
school.net/haroajapa009010.htm) under 推量, both seemingly sharing the same 未然形
+ む(ん) structure. However, the first one is glossed as negative, while the
second one translates in modern Japanese as a positive sentence.

> 推量…［～う・～だろう］
>
> 懈怠の心あることを **知らん** や。（徒然草・九二段）  
>  （怠けた心が生じることを **知らないだろう** か。）
>
> 夕には朝 **あらん** ことを思ひ、朝には夕 **あらん** ことを思ひて（徒然草・九二段）  
>  （夕方には明日の朝が **あるだろう** と思い、朝には夕方が **あるだろう** と思って）

Is there a reason for this? Or is this a mistake on the site editor's part?




The first example has 知らんや. It's important to note the ending particle や --
this is used in Classical Japanese after a suppositional ～む ending to indicate
a rhetorical question with an implied negative outcome, a bit like English
construction " _would_ he know that?" → implying that he wouldn't.

The あらん examples with ～ん (from older suppositional ～む) are not followed by
this same negative-rhetorical particle, so the translations into modern
Japanese phrasing do not include any negative sense.

See also:

  * [This Q&A](https://japanese.stackexchange.com/questions/28850/origin-of-the-word-%e7%83%8f%e6%9c%89/29148#29148) about the term [烏有]{いずくんぞあらんや}, which includes that same ～むや construction.
  * The Kotobank entries for や, such as [in Daijisen here](https://kotobank.jp/word/%E3%82%84-647430#E3.83.87.E3.82.B8.E3.82.BF.E3.83.AB.E5.A4.A7.E8.BE.9E.E6.B3.89), specifically sense 六.2.イ: 「2.文末用法。㋑反語を表す。…だろうか（いや、そうではない）。」




The first example has 知らんや. It's important to note the ending particle や --
this is used in Classical Japanese after a suppositional ～む ending to indicate
a rhetorical question with an implied negative outcome, a bit like English
construction " _would_ he know that?" → implying that he wouldn't.

The あらん examples with ～ん (from older suppositional ～む) are not followed by
this same negative-rhetorical particle, so the translations into modern
Japanese phrasing do not include any negative sense.

See also:

  * [This Q&A](https://japanese.stackexchange.com/questions/28850/origin-of-the-word-%e7%83%8f%e6%9c%89/29148#29148) about the term [烏有]{いずくんぞあらんや}, which includes that same ～むや construction.
  * The Kotobank entries for や, such as [in Daijisen here](https://kotobank.jp/word/%E3%82%84-647430#E3.83.87.E3.82.B8.E3.82.BF.E3.83.AB.E5.A4.A7.E8.BE.9E.E6.B3.89), specifically sense 六.2.イ: 「2.文末用法。㋑反語を表す。…だろうか（いや、そうではない）。」

