(Certainty: 3)

The translations available to us contain a significant number of passive verbs and suggest three methods for their construction: use of the progressive -do- prefix, use of the complex verb form kehn + verb, and use of the participial -ihj suffix.

Of the three methods, -do- passives appear in the widest variety of tenses and contexts. The particular difficulty of this passive construction, though, is that the exact same -do- in the active voice indicates a progressive tense. We confront a significant difficulty: if both verb forms are entirely identical, how do we know whether to read the verb as active or passive? Our only recourse, it would seem, is context, which itself is thorny territory. At best, the context will be clear and make sense; at worst, the meaning will be completely ambiguous.

An example will help illustrate this point, adopted from one of our known translations, which reads:

.rehbihshtah kodolahsahehn trehfilahdh tehflihn teegeht
The tunnel was sealed at the top in working order.

What is there to definitively indicate the passive voice of kodolahsahehn? Could not the sentence just as easily (indeed, more readily) be translated as:

The tunnel was sealing (itself) at the top in working order.

Perhaps the absense of a reflexive pronoun is here a hint to the verb's passivity. While this sentence is particularly ambiguous, the context of almost all other examples available to us, thankfully, is much more helpful in determining the verb’s voice, as in:

.khoy hehvtee meht dohooreet
If these words are found...

One of the first clues to the voice of the verb-in-context is the absence of a direct object when the verb in question is transitive. In the above example, the verb (hoor, to find) under normal circumstances would take a direct object. However, in its passive form, it does not, since what would semantically be the direct object of the verb if it were active becomes the passive verb's subject. Presumably, verbs that take more than one direct object would be an exception, with one object becoming the grammatical subject, the other remaining a verbal object. Without any examples, though, it is impossible to say for sure.

The complex verb form kehn + verb offers another method for marking passive voice. Of the three examples we have of this form, two conjugate the auxiliary kehn and the main verb with identical tense prefixes and actor suffixes (kokenen kohoorehn, kokenen kosaiehn); the third example conjugates them with the same tense prefixes but different actor suffixes (kokenen kopahzgo). This may indicate that the two verbs of the passive complex need not agree in all respects; alternatively, absence of an actor suffix on the main verb, while indicating first person singular, is less convincing of nonidentical conjugation than the presence of any other actor suffix would be.

Passives formed with the -ihj suffix are discussed at great length elsewhere. Briefly, their usage ranges widely in ways we don't entirely understand. It most offen appears in complex kehn + verb-ihj constructions; the passive infinitive is formed in this way (b'kehn + verb-ihj). One example exists of a conjugated passive verb (interestingly, a -do- verb) to which -ihj is suffixed.

A diversity of opinion exists on how, exactly, these three methods mark passivity – that is, in which aspects of these verbs the passive charge resides. One theory holds that it can be found predominantly in the actor suffixes, that, for example, in the sentence

.hehvtee meht dohooreet
These words are found.

the -eet suffix of hoor does not refer to hehvtee meht, but to an unspecified 3rd person actor, in this plural case, “some people.” Another way of more literally translating, keeping this in mind, would be

These words some people are finding.

We clearly see here the passive transformation of semantic direct object into grammatical verb subject; the meaning of the progressive translation is nearly equivalent to that of the passive. Similarly, with complex kehn + verb passives such as

.rehtiwah kolonehn kosaiehn t'tehlooknahvah garten
The shaft was designed by Surveyor's Guildmaster Garten.

the 3rd person actor, in this case tehlooknahvah garten, is referenced in the main verb's -ehn suffix, where the -ehn of kolonehn references the grammmatical subject, rehtiwah. As with all passives, the actor need not be explicitly mentioned in this sentence; it would then be implied in the main verb's -ehn suffix. According to this theory, if the actor, explicit or implied, were a different number or person, the main verb's suffix would change appropriately, as in

.rehtiwah kokenen kosai
The tunnel was designed (by me).

Another theory on the location of passivity holds that it resides in the overall form of the various constructions, that -do- passives indicate passivity through the prefix itself and are conjugated to agree with their grammatical subjects, and that complex kehn + verb passives indicate passivity through the unique complex verb form itself. This perspective helps explain why, for example, hehvtee meht dohooreet is conjugated as such in a context that would much more logically suggest a 2nd singular implied actor, in addition to more cleanly tying the third plural verb to an already-present 3rd plural subject, instead of inventing an additional 3rd plural actor to satisfy the demands of passivity. It cannot, however, account for passive constructions like kokenen kopazgo that depart from the formal design. And neither theory, to my eyes, can offer a satisfying explanation of the anomalous passivity of kotokituhehn in the one instance we have of the verb.

The final question, of course, is why there are multiple passive forms, and what the differences are between them. Unfortunately, we have yet to locate a satisfying answer. It has been suggested that the complex kehn + verb passive is a means of clearing ambiguity that could arise if a simpler passive form were used – yet in both clearly understood passives of this type, no such ambiguity arises if a simpler verb is used. Neither can the choice be linked to presence of the passive verb's actor or adverbial modification. While passive infinitives seem clearly expressed by the b'kehn + verb-ihj forms, the proper use of -ihj passives as functional verbs is just as inscrutible as the other passive forms.