A clause can have a subject you never hear. Ég vonast til að komast "I hope to get there," Það er gaman að dansa "It's fun to dance" — neither infinitive has a spoken subject, yet each has a perfectly definite one in meaning: in the first, I am the one who gets there; in the second, the dancer is people in general. Syntacticians call this silent subject PRO, and the question this page asks is the syntactic one: how is the missing subject interpreted, and how does Icelandic let you see a subject it does not pronounce? The answer reveals one of the language's most elegant tricks — predicate agreement makes silent subjects visible. (This is the Syntax-group treatment, focused on the interpretation of subject gaps; for the fuller argument-structure account of PRO and the subject/object-control verb classes, see infinitival clauses and PRO and raising, ECM, and control. For the other kind of subject gap — the one that licenses Stylistic Fronting — see stylistic fronting.)
Two ways to fill a silent subject: control vs arbitrary
Every subjectless infinitive gets its understood subject in one of two ways. Either it is controlled — its reference is fixed by a specific argument up in the matrix clause (obligatory control) — or it is arbitrary — no matrix argument controls it, and it means "one / people in general / anyone" (arbitrary control, often written PROarb). The difference is sharp: under control, the silent subject must be the controller and can be no one else; under arbitrary reference, the silent subject is generic and floats free.
Ég vonast til að komast á tónleikana.
I hope to make it to the concert. — OBLIGATORY (subject) control: the silent subject of 'komast' is controlled by the matrix 'ég'. The one who makes it is necessarily me — it cannot mean anyone else.
Það er gaman að dansa.
It is fun to dance. — ARBITRARY reference: there is no controller; the silent subject of 'dansa' is generic ('it's fun for anyone to dance / fun, dancing'). The 'það' is an expletive, not the dancer.
The contrast is the heart of the matter. In ég vonast til að komast, the gap is anchored to ég; in það er gaman að dansa, the gap is unanchored and reads as a generic "one." Syntactically, the difference is whether there is a matrix argument that must corefer with PRO (control) or none (arbitrary). The same silent-subject infinitive can flip between the two depending on the matrix frame.
Subject control and object control: who is the controller?
When the silent subject is controlled, the controller is either the matrix subject or the matrix object, and this is a lexical property of the matrix verb. Subject-control verbs (vonast til, ætla, ákveða, reyna, lofa) hand PRO to their subject; object-control verbs (biðja "ask," skipa "order," leyfa "allow") hand it to their object. The construction is otherwise identical — matrix … að + infinitive — so the controller is determined by the verb, not the shape.
Hún ákvað að fara ein.
She decided to go alone. — SUBJECT control: 'ákveða' hands the silent subject to its subject 'hún'; the goer is the decider. (Note 'ein' — feminine — agreeing with the silent subject; more on that below.)
Ég bað hann að koma snemma.
I asked him to come early. — OBJECT control: 'biðja' hands the silent subject of 'koma' to its OBJECT 'hann' (accusative). The one who comes is HIM, not me.
Kennarinn leyfði nemendunum að fara heim.
The teacher let the students go home. — object control: the silent subject of 'fara' is controlled by the object 'nemendunum' (dative); the ones who go home are the students.
Note that an object controller carries its own case (accusative hann with biðja, dative nemendunum with leyfa) — but that case belongs to the controller in the matrix clause, not to PRO. PRO's own features are revealed differently, through the predicate, as we will now see.
The payoff: predicate agreement makes the silent subject visible
Here is the depth competitors never reach. Icelandic predicate adjectives agree with their subject in gender, number, and (often) case. When the subject is the silent PRO, the predicate adjective still agrees with it — so the agreement morphology becomes a window onto a subject you cannot hear. The same infinitive að vera einn/ein/eitt "to be alone" surfaces in different forms depending on the gender and number of the silent PRO, and reading that form tells you who PRO is.
Hann vonast til að verða ekki einn um jólin.
He hopes not to be alone at Christmas. — PRO is controlled by masc 'hann', so the predicate 'einn' is MASCULINE singular. The silent subject's gender shows on the adjective.
Hún vonast til að verða ekki ein um jólin.
She hopes not to be alone at Christmas. — same frame, but PRO is controlled by fem 'hún', so the predicate is FEMININE 'ein'. The agreement tracks the gender of the silent subject.
Það er erfitt að vera einn í ókunnugri borg.
It is hard to be alone in a strange city. — ARBITRARY PRO: with no controller, the predicate defaults to MASCULINE singular 'einn' (the unmarked form for a generic 'one'). The agreement on a silent ARB subject is itself visible.
Stand the three side by side and the trick is laid bare. einn (masc), ein (fem) — controlled PRO inherits the controller's gender, and the predicate spells it out. And in the arbitrary case, einn surfaces in the default masculine singular: even a generic, controllerless silent subject carries enough featural content to make the predicate agree. Icelandic, in other words, morphologically sees a subject it never pronounces. (Some speakers also allow a neuter-singular eitt for a fully impersonal, sex-neutral generic — það er gott að vera frjáls "it's good to be free" with neuter agreement — but the masculine default is the standard arbitrary form.)
Stelpurnar vonuðust til að verða valdar í liðið.
The girls hoped to be picked for the team. — PRO is controlled by fem pl 'stelpurnar', so the participle 'valdar' is FEMININE PLURAL. Number as well as gender of the silent subject shows through.
Quirky case on a silent subject
The agreement window goes one step further and shows something startling: PRO can carry quirky (non-nominative) case, and a predicate or floating quantifier agreeing with PRO reveals that case. If the infinitive's verb assigns a quirky case to its subject — say leiðast "be bored," which takes a dative subject — then under control, a predicate adjective or quantifier agreeing with the silent dative PRO surfaces in the dative. The silent subject is invisible, but its case is not.
Hann vonast til að leiðast ekki einum á ferðalaginu.
He hopes not to be bored alone on the trip. — 'leiðast' assigns DATIVE to its subject, so the silent PRO is dative; the agreeing predicate 'einum' surfaces in the DATIVE masculine singular. The quirky case of the silent subject is visible on the predicate.
Það er leiðinlegt að leiðast einum allan daginn.
It's miserable to be bored alone all day. — arbitrary PRO bearing the dative that 'leiðast' assigns; the predicate 'einum' is dative, confirming PRO's quirky case even with no controller.
This is the deepest demonstration available that Icelandic case-marks subjects it does not pronounce: the dative on einum can only have come from agreement with a dative PRO, which in turn got its case from leiðast. No noun is spoken, yet the dative is right there on the predicate. (For the quirky-subject verbs themselves and the broader case story, the companion PRO page and the raising/control treatment go further.)
The subject gap, three ways
It is worth seeing that the "silent subject" here and the "subject gap" that licenses Stylistic Fronting are members of one family — Icelandic has several constructions where the subject position is unfilled, and each resolves it differently. A controlled PRO gap is resolved by a matrix controller; an arbitrary PRO gap is resolved generically; a relativised-subject gap (in þeir sem komnir eru) is resolved by the relative head and additionally invites Stylistic Fronting. Recognising that these are all "empty subject" phenomena ties the syntax together and explains why agreement morphology keeps reappearing as the tool that recovers the missing subject.
Þeir sem ætla að koma verða að skrá sig.
Those who intend to come must register. — TWO subject gaps nested: the relative 'sem [gap] ætla' (relativised subject), and inside it the controlled PRO of 'koma' (controlled by that same subject). Both gaps recovered, no overt pronoun anywhere.
Why this is hard for English speakers
The core concept — a silent infinitival subject — transfers fine, because English has it too ("I hope to make it"). What does not transfer is two things. First, the overt-pronoun trap: English sometimes allows or even prefers an overt subject in the embedded clause ("I hope that I make it"), and learners carry this over, inserting a pronoun where Icelandic control demands the silent PRO — \ég vonast til að ég komist is wrong as a control structure (you need ég vonast til að komast, with PRO). Second, and more subtly, English predicate adjectives *do not agree, so an English speaker has no instinct that the silent subject's gender, number, and even case are spelled out on the predicate — and so misses, or mis-sets, the agreement: að vera einn vs ein vs einum is a live choice that depends entirely on a subject you cannot hear. Train yourself to (a) leave PRO silent under control, and (b) read and write the predicate to match the silent subject's features.
Common Mistakes
❌ Ég vonast til að ég komist á tónleikana. (as a control structure)
Overt-pronoun trap — under control the embedded subject is the SILENT PRO; you don't insert 'ég'. Use 'Ég vonast til að komast'. (A finite 'að ég komist' clause is a different structure and not the natural control rendering.)
✅ Ég vonast til að komast á tónleikana.
I hope to make it to the concert.
The English habit of spelling out the embedded subject. Control requires PRO; don't fill it with an overt pronoun.
❌ Hún vonast til að verða ekki einn. (referring to a woman)
Agreement error — PRO is controlled by feminine 'hún', so the predicate must be feminine 'ein', not masculine 'einn'. The silent subject's gender controls the adjective.
✅ Hún vonast til að verða ekki ein.
She hopes not to be alone.
Predicate adjectives agree with the silent subject. A feminine controller forces a feminine predicate, even though no subject is pronounced.
❌ Það er erfitt að vera ein. (intending the generic 'one')
Agreement error for the arbitrary reading — generic/arbitrary PRO defaults to MASCULINE singular 'einn' (the unmarked form), not feminine 'ein'. Use 'Það er erfitt að vera einn'.
✅ Það er erfitt að vera einn.
It is hard to be alone. — arbitrary PRO takes the default masculine singular predicate.
Arbitrary PRO is not gender-free; its default agreement is masculine singular. The feminine ein would force a specific female referent, contradicting the generic reading.
❌ Hann vonast til að leiðast ekki einn. (with a quirky-case verb)
Quirky-case error — 'leiðast' assigns DATIVE to its subject, so the silent PRO is dative and the predicate must be dative 'einum', not nominative 'einn'. The silent subject's quirky case shows on the predicate.
✅ Hann vonast til að leiðast ekki einum.
He hopes not to be bored alone.
When the infinitive's verb assigns quirky case, PRO bears it, and the predicate agrees in that case — dative einum, not nominative einn.
Key Takeaways
- A subjectless infinitive has a silent subject, PRO, interpreted in one of two ways: obligatory control (a matrix argument fixes its reference — ég vonast til að [PRO] komast) or arbitrary/generic reference (það er gaman að [PRO] dansa, "for anyone").
- Under control, the controller is the matrix subject (ákveða, vonast til, lofa) or object (biðja, leyfa, skipa) — a lexical property of the verb. The controller carries its own matrix case; PRO's features show elsewhere.
- Predicate agreement makes the silent subject visible: að vera *einn / ein / eitt* reveals PRO's gender, valdar reveals plural number — Icelandic morphologically sees a subject it never pronounces.
- Arbitrary PRO defaults to masculine singular agreement (það er erfitt að vera einn), not gender-free.
- Quirky case shows on silent subjects too: with a dative-subject verb like leiðast, PRO is dative and the predicate agrees in the dative (að leiðast einum) — the deepest proof that Icelandic case-marks subjects it does not pronounce.
- English speakers err by inserting an overt pronoun where control needs silent PRO, and by missing predicate agreement (English adjectives don't agree). Leave PRO silent; match the predicate to the silent subject's gender, number, and case.
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- Infinitival Clauses and Implicit Subjects (PRO)C1 — How an að-infinitive clause with no spoken subject is interpreted. The silent subject — PRO — is read by SUBJECT control (Ég vil [PRO fara] 'I want to go'), OBJECT control (Ég bað hann [PRO að fara] 'I asked him to go'), or ARBITRARY/generic reading (Það er gott [PRO að hreyfa sig] 'it is good to exercise'). The startling Icelandic fact: PRO can carry QUIRKY CASE — a predicate adjective agreeing with a silent dative PRO surfaces in the dative — proving that case is assigned even to subjects you cannot hear. When the lower subject is coreferent with the matrix one, an OVERT pronoun is wrong; PRO is required.
- Raising, ECM, and ControlC1 — The three infinitival constructions that organise Icelandic complementation: subject-to-subject RAISING (virðast 'seem' — the lower subject moves up and keeps its case, so a quirky dative stays dative), Exceptional Case Marking / accusative-with-infinitive (ECM: telja 'believe' assigns accusative to the embedded subject — tel hann vera góðan), and CONTROL (a silent PRO coreferent with a matrix argument — lofa að koma). Case preservation under raising is the clinching evidence for quirky subjecthood and the centrepiece of the Icelandic syntax literature.
- Stylistic Fronting in DetailC1 — Stylistic Fronting (stílfærsla) is the operation that fills an empty subject slot in a clause with a fronted participle, predicate, particle, or negation — þeir sem KOMNIR eru 'those who have come', sá sem EKKI vinnur 'the one who does not work'. Its hallmark is the SUBJECT GAP: it appears precisely where the subject position is empty (relative clauses, subject questions), and never in ordinary that-clauses with a full subject. This subject-gap requirement makes it a diagnostic of the empty subject position and distinguishes it sharply from topicalisation — a uniquely Scandinavian phenomenon that gives formal Icelandic its characteristic inverted ring.