Accusative-and-Infinitive Clauses


Staff member
An accusative-and-infinitive clause (also known by the Latin term accusativus cum infinitivo, or AcI for short) is a clause with a subject in the accusative and a verb in the infinitive. Many beginner-to-intermediate students will be familiar with the use of this construction in indirect statements, as this is taught at some point in pretty much every basic Latin course (those of you who are not familiar with accusative-and-infinitive indirect statements or feel the need to review the concept may take a look at the dedicated article by Ignis Umbra here). Beginner-to-intermediate or even relatively advanced students will not, however, necessarily be aware of all the other uses of the construction.

All its uses are based on the same principle. The purpose of this post is to explain that overarching principle and provide examples of its application in a few different contexts.

The principle is as follows:

An infinitive can work as a noun would, notably as the subject or object of a verb. For example: Turpe est mentiri, “It is ugly to lie”, “Lying is ugly”. Here, mentiri is the subject of est. (Note that, while in English “it” is technically the subject in “It is ugly to lie”, this “it” is only what is called a dummy subject, anticipating the “true” subject that comes later, “to lie”. To lie is truly what is ugly.)

Now, a whole infinitive clause, complete with subject, can also be used as a noun. When that happens, the subject (along with any adjective or the like that goes with it) of the infinitive is put in the accusative, and that is what we call an accusative-and-infinitive clause. This kind of clause is found in indirect statements, for instance:

Solere aiunt reges barbaros Persarum ac Syrorum pluris uxores habere (Cic. In Verrem 2.3.76), literally, “They say the barbarian kings of the Persians and Syrians to be wont to have several wives”, i.e. “They say that the barbarian kings of the Persians and Syrians customarily have several wives.” Here, the accusative-and-infinitive clause solere reges barbaros Persarum ac Syrorum pluris uxores habere is the object of the verb aiunt.

But not only. Here are examples of other uses:

Non est bonum esse hominem solum (Gen. 2:18), “It is not good (for) the man to be alone”; “It is not good that the man should be alone”. Here, the substantive clause, or noun clause, esse hominem solum is the subject of the verb est.

Pastorem [...] pascere oportet ovis (Verg. Ecl. 6.5), “It is necessary/proper (for) a shepherd to feed the sheep”, “A shepherd must feed his sheep”. Here too, the clause pastorem pascere ovis is the subject of oportet.

Accusative-and-infinitive subject clauses occur most often with impersonal verbs (like oportet, patet, praestat, licet…), esse, and passive declarative verbs in the perfect tenses (perfect, pluperfect and future perfect)*. They can also occur with other verbs and indeed theoretically with any verb; but you’ll understand that with some verbs it would rarely, if ever, make sense. Take the sentence Caesarem consulem fuisse saltat, “For Caesar to have been a consul dances”: it’s grammatically correct but hardly meaningful. (In addition, the construction might in some situations be more meaningful than this but unidiomatic; that's case by case, though.)

Sometimes, a substantive infinitive clause has no stated subject, but only an adjective, noun, or the like, referring to a kind of implied general subject like “someone”. Here too, the adjective (or noun, etc.) must be in the accusative. Examples:

Si turpitudo malum est, et turpem esse malum est (Sen. Ep. Mor. 19.117.7), “If ugliness (of behavior) is an evil, then being ugly (in one’s behavior) is an evil, too.” Turpem esse is the subject of est. Indeed, you will notice that turpem esse grammatically works in just the same way as the noun turpitudo in the first part of the sentence — that’s why it’s called a substantive clause or noun clause: it works as a substantive or noun.

Nescire autem quid ante quam natus sis acciderit, id est semper esse puerum (Cic. Or. 34), “Not to know what happened before you were born, that is always to be a child”. Here, the substantive clause semper esse puerum works as a predicative complement to the verb est. Again, like all substantive clauses, it works as a noun: note how easily it could be replaced by the nominative noun phrase perpetua pueritia.

It is sometimes felt as counterintuitive that the subject of the infinitive in such clauses should be accusative rather than nominative. There is, however, a certain logic to it. It will no longer seem so strange if you realize that the Latin nominative is not, in fact, the case of every subject (and its adjectives and/or complements), but the case of the subject (and its adjectives and/or complements) of the finite (i.e. conjugated) verb.** In a sentence such as mendacem esse vitium est, “To be a liar is a flaw”, if you had mendax instead of mendacem, mendax would need to be or refer to the subject of the only finite verb that’s there, est, and the sentence wouldn’t make any sense because what would the infinitive esse be doing there, then? The subject of this est is not a person; the flaw is not a liar or the implied “someone” subject. The flaw is the fact of being a liar, the whole clause “to be a liar”, mendacem esse. So that is the subject of est. By turning the subject of the infinitive and the words agreeing with it into the accusative (there is no explicit subject in this particular phrase, but you can still see the accusative in the adjective mendacem that agrees with a kind of very remotely implied aliquem), you enable the whole clause to become something that works as a noun.

One thing that can cause confusion is that an adjective or noun etc. referring to the implied subject of an infinitive is in the nominative when the subject of the infinitive is the same as the one of the main verb, and there is no accusative pronoun going with the infinitive to refer back to that subject. This often (but not exclusively) happens with verbs of wishing: vis beatus esse, “You wish to be happy”; ego nolo Caesar esse (from a poem by a certain Florus quoted in the Historiae Augustae), “I don’t want to be Caesar”; cupit fortis videri, “He wants to appear courageous”. Verbs of wishing sometimes take an accusative-and-infinitive clause even when referring back to the subject of the verb of wishing — things like cupio me eligi, “I want me to be chosen”, i.e. “I want to be chosen” — but it is rarer. Conversely, while verbs of saying usually take the accusative-and-infinitive construction in all cases, even when the subject of the infinitive is the same as that of the verb of saying, they occasionally take the same nominative-and-infinitive construction that was exemplified above with verbs of wishing. This happens mostly in poetry, probably in imitation of Greek, where this construction is regular. For example, Catullus (Car. 4) wrote: Phasellus ille […] ait fuisse navium celerrimus, “That (famous) Phasellus says/claims to have been the fastest of ships”, “… says that he used to be the fastest of ships”. In usual Latin, that would be ait se fuisse navium celerrimum.

So, to sum up the basic rule: when the subject of the infinitive is left implied (i.e. not represented by any pronoun like me, te, se...) and is the same as the subject of the main verb, then any adjective etc. referring to the subject that is common to both the infinitive and the finite verb goes in the nominative (e.g. Publius vult rex esse, “Publius want to be the king”). However, when a pronoun represents the subject of the infinitive, then you get a regular accusative-and-infinitive clause (e.g. Publius putat se esse regem, “Publius thinks himself to be the king”, “Publius thinks he’s the king”).

Lastly, let me specify that accusative-and-infinitive clauses aren’t the only substantive clauses in existence — they are, however, the only ones that constitute the topic of this thread. ;)

*Passive declarative verbs in present-stem tenses (i.e. present, imperfect and future simple) are more usually constructed with the nominative and infinitive. So, for instance, while a sentence like dictum est Ciceronem praeclarum oratorem fuisse, “It has been said that Cicero was an outstanding orator”, would be perfectly fine, in the present tense it would more usually be dicitur Cicero praeclarus orator fuisse, “Cicero is said to have been an outstanding orator”. “It is said that Cicero was an outstanding orator” is also an acceptable translation, but in Latin one more usually uses the literal equivalent of the first one (“Cicero is said to…”).

**Historical infinitives are an exception: they take nominative subjects. A clause with a historical infinitive isn’t a substantive clause, and therefore does not require an accusative subject.
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Staff member
As a post scriptum, it might be worth mentioning the idiomatic use of the accusative-and-infinitive construction in titles. The title of a book or chapter can be a noun, right? Well, when you want to make a whole fact your title, one (though not the only) thing you can do is turn it into a noun of sorts by making it accusative and infinitive, and that'll be your title. For example, a chapter in your Epicurean philosophical book could be titled voluptatem summum bonum esse, "[On] (the fact that) pleasure is the highest good".

Another thing that deserves a quick mention is the exclamatory use of the accusative-and-infinitive: an accusative-and-infinitive clause can be found on its own with an exclamatory meaning, usually conveying indignation or disbelief. E.g. heu, talem virum damnatum esse! "Alas, that such a man should have been condemned!" It is not rare for such a clause to take the interrogative particle -ne, which makes it partly a question. E.g. mene ita deceptam esse? "Me, to have been thus deceived?" "That I should have been thus deceived!" This construction probably arose through the ellipsis of some verb (of perception or the like) constructed with the accusative-and-infinitive.
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Dr. Freud
"...also known by the Latin term accusativus cum infinitivo, or NcI AcI for short)..."


Staff member
Yeah, sorry, I was just going to correct that.