The Instrumental of Agent

You already know the instrumental as the case of the tool — писа́ть ру́чкой "to write with a pen," with no preposition (see means and instrument). This page extends that same logic to one of the most important and least intuitive uses for English speakers: marking the agent of a passive sentence — the doer that English introduces with the word by. The house was built by workers becomes Дом постро́ен рабо́чими, with рабо́чими in the bare instrumental and nothing standing in for "by." The deep payoff of this page is a single unifying idea: in Russian the tool, the agent, and the impersonal force of nature all wear the same instrumental case, because Russian conceives all three as "the means or force through which the action happened." There is no Russian word for "by [an agent]" — there is only the instrumental.

The agent in a participial passive

The most common written passive uses a short-form past passive participle (постро́ен, напи́сан, откры́т) plus the agent in the instrumental. Compare the active and the passive of the same event:

Watch what moves. In the active, the doer is the nominative subject and the thing-acted-on is the accusative object. In the passive, the thing-acted-on becomes the nominative subject (Дом, Кни́га, Аме́рика), the participle agrees with it in gender and number (постро́ен, напи́сана, откры́та), and the original doer drops into the instrumental — рабо́чими, а́втором, Колу́мбом. No preposition appears anywhere.

The -ся passive and its agent

Russian's second passive — the reflexive -ся passive, used especially with imperfective verbs and ongoing processes — also takes its agent in the instrumental. Here the verb carries the -ся suffix and the subject is again the thing acted on:

Whether the passive is built with a participle (Дом постро́ен рабо́чими) or with -ся (Дом стро́ится рабо́чими), the agent rule is identical: bare instrumental, no preposition. The two passives differ mainly in aspect and register — the -ся passive favours imperfective, ongoing actions — which is the subject of the -ся passive in detail. For the participle forms themselves, see passive participles and short-form passive participles.

The impersonal force: accidents and nature

Now the use that ties the whole case together. Russian has a vivid impersonal accident construction in which there is no subject at all — the verb sits in the neuter singular and the force responsible is in the instrumental. This is how Russian describes things that happen to someone or something through a blind natural force: wind, lightning, snow, a current.

Notice how naturally this flows from the same case. A human agent (рабо́чими), an inanimate force (ве́тром, молни́ей), and a plain tool (ножо́м) are, to a Russian ear, the same kind of thing: the means or power through which the action came about. English splits them — with a knife, by the workers, by the wind — but Russian sees one role and gives it one case. That is the insight to carry away: there is no Russian word for "by" in these constructions, because the instrumental already says it.

Register: when Russian actually uses the passive

A practical warning for B2 learners: the participial passive (Дом постро́ен рабо́чими) is largely a (formal) and (academic) device — news reports, official notices, scholarly prose, history. In everyday (informal) speech, Russians usually avoid naming an agent at all and prefer the indefinite-personal construction — a 3rd-person-plural verb with no subject (Дом постро́или "they built the house / the house was built"). So while the instrumental-agent rule is non-negotiable when you use a full passive, in casual conversation the whole agent phrase is often simply dropped. Knowing this keeps you from sounding like a legal document at the dinner table; the stylistic choice is covered on passive and impersonal style.

How this differs from English

English handles the passive agent with one fixed preposition: by. Written by Pushkin, destroyed by fire, approved by the committee — always by, and the noun after it never changes shape. Two things trip up English speakers translating into Russian. First, they reach for a preposition to render "by" — and there isn't one for the agent; the case alone does it, so постро́ен от рабо́чих or постро́ен с рабо́чими are both wrong, and рабо́чими (bare instrumental) is right. (Note the contrast with с + instrumental, which means together with — чай с са́харом — a completely different relationship.) Second, English keeps by even for natural forces (killed by lightning), so learners don't notice that Russian unifies the willed agent and the blind force under one case. The cure is to stop thinking "translate by" and start thinking "this is the means/force through which — that's the instrumental."

Common Mistakes

Key Takeaways

• The passive agent — English's "by"-phrase — goes in the bare instrumental with no preposition: Дом постро́ен рабо́чими, Кни́га напи́сана а́втором, Аме́рика откры́та Колу́мбом.
• This holds for both passives: the participial passive (постро́ен + instrumental) and the -ся passive (стро́ится + instrumental).
• The participle/verb agrees with the new subject (the thing acted on), never with the agent.
• The impersonal accident construction puts the natural force in the same instrumental, with a subjectless neuter verb: Кры́шу сорва́ло ве́тром, Доро́гу занесло́ сне́гом. Tool, agent, and force share one case — there is no Russian word for "by."
• Beware с + instrumental ("together with") — it is not the agent. And remember the full participial passive is mostly (formal/academic); casual speech prefers the agentless indefinite-personal (Дом постро́или).