Contrary to the popular beliefs, Old Japanese (and proto-japanese) had the active-passive alignment instead of the accusative-nominative aligment it (supposedly) has today.
Transitivity of the verbs of change (henka dousi)
Most verbs of change have two variants, one being intransitive (representing an action of being changed/impacted), and one transitive (representing an act of causing something/someone to change). Here are some examples:
| original verb | intransitive form | transitive form | meaning |
|---|---|---|---|
| hajim.u | hajim.aru | hajim.eru | to start |
| nig.u | nig.eru | nig.asu |
Having this duality might seem a bit odd, given that old-japanese had only one form for these verbs. Given old japanese tended to omit case-marking particles, it might seem odd not to know if the noun is being the subject or the object of an action
The active-passive model
- Agent - the active doer of an action, someone who makes the impact
- Patient - the passive receiver of an action, someone (involuntarly) impacted by the action
On the surface, it might look like these are just synonyms for subject and object, however they represent semantic function instead of syntactical one. As an example, making a sentence use passive voice changes the subject, but it doesn't change the agent
The key piece of info is that verbs of action have an obligatory agent and optional patient, while verbs of change have an obligatory patient and optional agent. Using this model also means there's no case switching for transitive-intransitive pairs:
jugyou ga hajimatta class.PAT finish.PAST sensei ga jugyou wo hajimeta teacher.AGT class.PAT finish.PAST
Alignment with old japanese verb classes
Another piece of info supporting this claim might be that the two main old japanese verb clases (nidan and yodan) correlate really well with the action-change verb split.
Nidan verbs are mostly verbs of change, while yodan verbs are mostly verbs of action. Some action verbs do belong to the nidan class, however they are almost always more polite/formal versions of other action verbs which belong to the yodan class. This might suggest that even in old japanese, making the subject patientive was a way of making a sentence more polite.