§452. Infinitive Mood

The Infinitive, with or without a subject accusative, may be used with est and similar verbs (1) as the Subject, (2) in Apposition with the subject, or (3) as a Predicate Nominative.¹

• As Subject:—

  • dolēre malum est (Fin. 5.84), to suffer pain is an evil.
  • bellum est sua vitia nōsse (Att. 2.17), it's a fine thing to know one's own faults.
  • praestatcompōnerefluctūs (Aen. 1.135), it is better to calm the waves.

• In Apposition with the Subject:—

  • proinde quasi iniūriamfacere id dēmum esset imperiō ūtī; (Sall. Cat. 12), just as if this and this alone, to commit injustice, were to use power. [Here facere is in apposition with id.]

• As Predicate Nominative:—

  • id est convenienter nātūrae vīvere (Fin. 4.41), that is to live in conformity with nature. [Cf. ūtī in the last example.]

• istuc ipsum nōn esse cum fueris miserrimum putō; (Tusc. 1.12), for I think this very thing most wretched, not to be when one has been. [Here istuc ipsum belongs to the noun nōn esse.]
• miserārī,invidēre,gestīre,laetārī, haec omnia morbōs Graecī appellant (id. 3.7), to feel pity, envy, desire, joy,—all these things the Greeks call diseases. [Here the infinitives are in apposition with haec.]

a. The infinitive as subject is not common except with est and similar verbs. But sometimes, especially in poetry, it is used as the subject of verbs which are apparently more active in meaning:—

• quōs omnīs eadem cupere, eadem ōdisse, eadem metuere, in ūnum coēgit (Iug. 31), all of whom the fact of desiring, hating, and fearing the same things has united into one.
• ingenuās didicisse fidēliter artīs ēmollit mōrēs (Ov. P. 2.9.48), faithfully to have learned liberal arts softens the manners.
• posse loquī ēripitur (Ov. M. 2.483), the power of speech is taken away.