ARE: Lesson - Uses of the Infinitive - Complement

The image shows a painting of gladiators fighting.

Uses of the Infinitive - Complement

Let's continue our exploration of the infinitive by learning about the infinitive as the complement of a verb. The term complement derives from the Latin verb compleo, complere - to fill, finish. A complement finishes the thought of a verb. It is being used very broadly in this sense so that the term includes using an infinitive as a direct object or as a true complementary infinitive.

The image depicts two gladiators in combat. It is part of a mosaic from the Villa at Nennig (found in modern day Germany) and dates to the 2nd or 3rd century CE. It is referred to as "Retiarius stabs secutor". Do you think that the retiarius was able to defeat the secutor?

Infinitive as Complement

Did you notice the phrase: was able to defeat in the sentence above? The infinitive to defeat is a complementary infinitive.

Complementary uses of the infinitive are more common than subject infinitives. There are two distinct, but closely related, forms:

  1. The direct object infinitive (following transitive verbs like cupere, timere, constituere, etc.)
  2. The complementary infinitive (following verbs like posse and debere)

Direct object infinitives complete transitive verbs (verbs which take a direct object) while complementary infinitives are used to complete a special kind of intransitive verb called a modal verb.

How can you tell the difference between a transitive verb and a modal verb? Ask a simple question: do I have to use an infinitive here? If that infinitive can be replaced with another noun or a pronoun, you are working with a transitive verb and the infinitive is a direct object. If, however, there is no other form that could go in the place of the infinitive, you are working with a modal verb and it is a complementary infinitive. Since both the direct object and complementary infinitive complete another verb, we group them together and call the group complementary. 

Nota bene: this is quite a bit deeper than you really need to go right now - we are mainly concerned with seeing how infinitives work and wanted to provide some background, but don't let yourself get to bogged down here. If you are feeling overwhelmed, just remember: infinitive = to + verb, whether a subject, direct object or complementary infinitive!

Infinitive as a Complement - Examples

Direct Object Infinitive Examples

Complementary Infinitive Examples
  • Manere cupivimus.
    • We wanted to stay. (infinitive as DO)

Note: the infinitive manere can be replaced by a noun, like this:

  • Cenam cupivimus.
    • We wanted dinner. (regular noun as DO)
  • Venire non possumus.
    • We are not able to come.
    • We cannot come.
  • Te manere cupivimus.
    • We wanted you to stay.

Note: "Te" is accusative as the subject of the infinitive. Direct object infinitives can use an accusative subject, but true complementary infinitives cannot.
  • Gladiatores videre bene poteram.
    • I was able to see the gladiators well.
    • I could see the gladiators well.
  • Spectare ludos constituit.
    • He decided to watch the games.
  • Liberos curare debetis.
    • You ought to care for the children.
    • You should care for the children.