Confusion regarding 'esse' + accusative

Question

I am currently learning Latin from the Bloomsbury Latin to GCSE books. In one of the reading passages the following constructions are used:

"non cupio rex vester esse. dei signum mittent si me regem esse cupiunt."

I have translated this as "I do not want to be your king. The gods will send a sign if they want me to be king." I am perplexed as to why, in the second sentence, 'regem' is used instead of 'rex'. I was under the impression that verbs of existence, including the infinitive, take the nominative case and indeed in the first sentence the infinitive appears to do just that.

I have noticed that there are a few mistakes in this text so the explanation might be nothing more complex than that, but still I wanted to ask.

Many thanks in advance.

Answer 1

It's not that esse takes the accusative—it's that cupiō takes the accusative, and esse links two things in the same case. In other words, regem is accusative because mē is accusative, and mē is accusative as the object of cupiunt.

This is a fairly common construction in Latin, called the "accusative with infinitive" (or accusativus cum infinitivō if you prefer). In general, when you want to use a whole clause as the direct object of a verb in Latin, you'll put the subject of the clause into the accusative case, and the main verb of the clause into the infinitive mood. Both the subject and the infinitive then act as objects of the verb. This can often be translated very literally into English ("I am king" → "the gods want me to be king"), though sometimes it can sound a bit archaic ("it is true" → "search your feelings, you know it to be true").

(This does, by the way, create some ambiguity, since a direct object within that clause will also be in the accusative. According to Ennius, the Oracle of Delphi exploited this ambiguity: when Pyrrhus asked if he would win the war, she said aiō tē, Aeacidā, Rōmānōs vincere posse.)

This explains why mē is accusative; regem is then accusative because esse wants the same case on both sides. This is usually the nominative, but that's just because the nominative is the "default" case for a Latin noun; if some other word forces one of esse's nouns into a different case (like the accusative here), the other noun will follow it.

So why isn't the first rex accusative too? Because esse is linking it with the (implied) subject of cupiō, and as the subject of a finite verb, that subject goes into the nominative case. You can imagine a hidden ego in there.

Answer 2

Cupere is a special kind of verb. You can use it to talk about something the subject of the sentence wishes to do himself. In that case you use an infinitive as the object and predicate nouns or adjectives are in the nominative:

Cupit rex esse.
He wants to be king.

Normal objects are in the accusative as usual, though:

Cupio placentam edere.
I want to eat cake.

Or you can use cupere to talk about something the subject wishes someone else would do. In that case you use an accusativus cum infinitivo or AcI for short. It is a whole sentence, but the subject is in the accusative, and the verb is an infinitive:

Cupit me regem esse.
He wishes that I am king.

Objects stay in the accusative too:

Cupio te placentam edere.
I wish that you eat cake.

Other verbs like that are velle, nolle, malle, studere, desiderare.

There are also verbs that can only talk about something the subject does himself, not someone else, like audere (dare), conari (attempt), and a few others. These can only stand with an infinitive, not an AcI:

Conor verax esse.
I try to be honest.

And of course there are also verbs that only talk about things other people do. They stand with the AcI:

Iubet me venire.
He orders me to come.

The AcI is also the construction for indirect speech, standing with verbs of thinking, feeling, saying, even when the subject is the same as in the main clause.