Why isn't ある's negative form あらない?

Question

ある is listed in dictionaries as having ラ行五段活用, which would suggest a negative form of あらない. However, that form does not exist. Why not?

Answer 1

In modern Japanese, instead of the conjugation [未然形]{みぜんけい}+[無]{な}い, another word is used to express the plain negative, namely 無い.

This a process called suppletion, supplying a certain conjugational form with a different word. It exists in English as well. You don't say good and gooder, you talk about better, which comes from Proto-Indo-European *bhAd- good. Further examples include bad - worse, and be - is - was.

However, this kind of conjugation exists in Classical Japanese. Here the negative is expressed via 未然形+ず, and ある is no exception: あらず. ず , or perhaps better known in its form ぬ, is the helper verb of negation.

「[舟]{ふね}は[水]{みず}に[非]{あら}ざれば[行]{ゆ}かず。[水]{みず}、[舟]{ふね}に[入]{い}れば[則]{すなわ}ち[没]{ぼっ}す」

Even in modern Japanese, you can still say あらへん (Kansai dialect).

Lastly, although rare, there are attested instances of the form あらない (see 日本国語大辞典, entry あらない)

せく事はあらない

土佐【とさ】とて鬼の国でも蛇【へび】の国でもあらないものを

There is also あらなくに, but the な here is analyzed as the く-nominalization of ず.

Answer 2

To my knowledge, this is historically shrouded in mystery, so there is no authoritative answer. (I'd be very interested in hearing one myself.)

This page speculates (in, unfortunately, a very authoritative tone, yet with no citations...) that the negation of ある (あらない) did at one point exist, but was discarded for the antonym of ある (ない). (N.B., we do at least know that another negation of ある (あらず), did exist historically, so the first part of this claim isn't too hard to believe.)

Their reasoning goes something like...

word    negation   antonym
開く     開かない　　　閉める
大きい　　大きくない　　小さい
ある　　　あらない　　　ない 

In these cases, none of the negations match the antonym ("to not open" != "to close", "not big" != "small") except for ある, and since ない is shorter, the あらない form was discarded.

---

I don't know if I entirely buy their argument or not. It seems logical but honestly anything could have happened historically for us to end up in our current position, so I'd personally be reluctant to actually subscribe to this theory without any evidence.