Impersonal passive voice

The impersonal passive voice is a verb voice that decreases the valency of an intransitive verb (which has valency one) to zero.
The impersonal passive deletes the subject of an intransitive verb. In place of the verb's subject, the construction instead may include a syntactic placeholder, also called a "dummy". This placeholder has neither thematic nor referential content. (A similar example is the word "there" in the English phrase "There are three books.")
In some languages, the deleted argument can be reintroduced as an "oblique argument" or "complement".
Test of unergative verbs.
In most languages that allow impersonal passives, only unergative verbs may undergo impersonal passivization. Unaccusative verbs may not. The ability to undergo this transformation is a frequently used test to distinguish unergative and unaccusative verbs. In Turkish, for example, the verb "çalışmak" "to work" is unergative and may therefore be passivized:
The verb "ölmek" "to die", however, is unaccusative and may not be passivized:
In a passive construction with an unergative verb, the unexpressed agent is understood to be an indefinite human agent.
Examples.
Dutch.
The Dutch impersonal passive can be seen in the following sentences.
German.
German has an impersonal passive voice, as shown in the examples below:
Active voice:
Impersonal passive voice:
In the latter example, the subject ("Die Kinder", "the children") has been deleted, and in its place is the dummy "es" "it".
The sentence can be constructed without an overt subject by placing an adverbial in the first position:
Venetian.
Venetian has the impersonal passive voice, also called intransitive passive, since it is built from intransitive verbs.
The verb "parlar" "to speak" is intransitive and takes an indirect object marked by "a" "to" or by "co" "with": although there is no direct object to be promoted to subject, the verb can be passivized becoming subjectless, i.e. impersonal. The usual auxiliary "to be" is employed, in the form "xe" "is" (with zero-dummy) or in the form "gh'è" "there is" (with gh'-dummy) depending on the local variety.
Likewise, the verb "tełefonar" "to phone / to ring up" takes a dative indirect object in Venetian (marked by "a" "to"), still it is often used in the impersonal passive:
Differently from Dutch, the subject can be introduced only with the active voice:
Latin.
Impersonal passive constructions are quite common in Latin. While transitive verbs can appear in the impersonal passive, intransitives are much more likely to. One notable example is a phrase from Virgil:
It is translated "thus one goes to the stars" (i.e. "such is the way to immortality") or "thus you shall go to the stars" but the word "itur" is the passive form of "ire" ’to go’ in the third person singular, so its literal meaning could be rendered like "this is how it gets gone to the stars."
Similarly, "Saltatur" is literally the third person singular passive form of the verb "saltare" ’to dance,’ and it means "they (or: people) are dancing" or more precisely, "it is being danced". "Pugnatum est" is a perfect passive form of the verb "pugnare" ’to fight’, so this form means "they (or: people) were fighting" or "there was a fight going on" or even more precisely, "it was fought" or "it has been fought."
Another example is the answer to the question "Quid agitur?" (approx. "what's up?", lit. "what is being done?") in a play by Plautus: "Vivitur," approx. "not too bad", literally: "one is alive" or more precisely, "it is being lived", from the impersonal (intransitive) verb "vivere" (’to live’).
Slavic.
Slavic languages have the impersonal passive, formed with the reflexive particle (the examples below are in Serbian):
The verb is in the third person singular (compare with Latin "saltatur") As with other impersonal forms, the past tense forms are in neuter singular:
No dummy pronoun can be used. There appears to be no restriction like in Turkish, e.g. the verb "to die" can be put into impersonal passive as well.