If you’re learning Japanese, you’ve probably noticed that potential and passive forms follow different patterns. With godan verbs like 書く, we say 書かれる (kakareru), but with ichidan verbs like 食べる, we say 食べられる (taberareru). Why this difference? Let’s dive into the historical development that led to these patterns.
The A-Stem Connection
The key to understanding these patterns lies in the “a-stem” (未然形, mizenkei) system of Old Japanese. As Tetsuya Asakawa explains in his study:
未然形の最後の音節がア段音か非ア段音かによって、「れる・られる」のどちらが接続されるかが決定されるのが本来の日本語文法である。
(The original Japanese grammar determined whether to use reru or rareru based on whether the final syllable of the verb stem was an a-row sound or not.)
Historical Evolution
The system we use today evolved from more complex patterns in Old Japanese (上代語). Bjarke Frellesvig’s “A History of the Japanese language” reveals that both passive and causative forms underwent significant changes:
In Old Japanese:
- Passive: -(a)ye-
- Causative: -(a)sime-
These evolved into:
- Passive: -rare-
- Causative: -sase-
A particularly interesting transition occurred during the Early Middle Japanese period (中古日本語). Frellesvig notes:
During the EMJ period, the OJ passive -(a)ye- and causative -(a)sime- went out of use and were replaced by the alternative OJ passive -(a)re- and the causative -(a)se-
We can still see traces of these older forms in modern Japanese. For example, the modern word 見える (mieru, “to be visible”) comes from the Old Japanese passive form 見ゆ (miyu).
The System’s Logic
The grammar required an “a” sound environment before attaching auxiliary verbs, which explains why らin られる was necessary for some verbs but not others. This wasn’t a random rule but rather a systematic phonological pattern that made the language more regular.
Today’s patterns preserve this ancient phonological requirement:
Sources
A History of the Japanese language by Bjarke Frellesvig
https://tokyo-metro-u.repo.nii.ac.jp/record/9769/files/20028-008-002.pdf
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