Grammatical changes due to 歷史假名遣 use?


basically, I am wondering to what extent use of 歷史假名遣 before 1946 would
influence grammatical forms in texts from the period between roughly 1900 to
1946. As I understand it, most 歷史假名遣 pertains to parts of words usually
written in kanji anyways (e.g. 今日). I also understand that 歷史假名遣 also has an
impact on certain verb endings though. That seems straightforward for forms
like ている --> てゐる, as this change just reflects replacing い with ゐ. However, as
I understand it, verbs ending in う in modern Japanese end in ふ with when using
歷史假名遣. But does 歷史假名遣 have any major impact on conjugation?

For instance, I would think that 思う-->思ふ would be negated 思はない using 歷史假名遣.
However, I have also seen the form 思はず as the negative form of 思う in older
texts.

Basically, I want to know whether 歷史假名遣 in pre-1945 texts have any impact on
grammar (instead of just on orthography) if the text in question otherwise
follows modern Japanese grammar.

Thanks!




Grammar and kana orthography are two different things. By definition, kana
orthography only defines the **spelling** of words, and it says nothing about
grammar. 思わない and 思わず are two different types of negation, and the difference
lies not in kana orthography but in grammar. 思わない and 思はない are exactly the
same phrase written in two different kana orthographies.

In terms of grammar, 1900-1946 was a transitional period from [classical
Japanese grammar](https://www.tofugu.com/series/kobun-guide/) to modern
Japanese grammar (see [_genbun
itchi_](https://en.wikipedia.org/wiki/Genbun_itchi)). In this period, you
would see many novels written in **modern** grammar but with **historical**
kana orthography. For example, [Natsume Soseki's
吾輩は猫である](https://en.wikipedia.org/wiki/I_Am_a_Cat) was first published in 1905
in modern grammar and with historical kana orthography (see the picture in
[this article](https://serai.jp/hobby/1051788)), but the same novel _can_ be
written in modern kana orthography, too. People today actually read this novel
usually in modern kana version [like
this](https://www.aozora.gr.jp/cards/000148/files/789_14547.html). Things
written before 1900 were written in classical grammar and historical kana
orthography, and things written after 1946 are normally written in modern
grammar and modern kana orthography.

Theoretically speaking, it _is_ also perfectly possible to write a news
article issued today in historical kana orthography, but no one do that
because it's meaningless.

**EDIT** : German also underwent a major [orthography
reform](https://en.wikipedia.org/wiki/German_orthography_reform_of_1996)
relatively recently, but this does not mean people suddenly changed how they
speak German in 1996.

