What Is a Passive Infinitive?

In English grammar, the passive infinitive is an infinitive construction in which the agent (or performer of the action) either appears in a prepositional phrase following the verb or is not identified at all. It is also called the present passive infinitive.

The passive infinitive is made up of the marker to + be + a past participle (also known as the -ed or -en form), as in "The case is to be decided by a judge."

Passive Versus Active Infinitive Sentence Construction

But let's back up to first show just what passive construction (also called passive voice) is. A sentence constructed in a passive manner may not have a clear subject doing the action of the verb. Take this passive sentence: "A cheer was heard from the field." There is no actor that goes with the verb was heard. You could make it active by using a better verb and adding a subject to construct the following: "A cheer rose from the field," or "I heard the cheer from the field." Better still would be to add a more specific subject if it is known (and thus add more detail and imagery), such as in "The fans on the visitors' side of the field cheered." 

If the subject had been identified but the sentence was still passive, it could have read, "A cheer by the fans on the visitors' side was heard from the field" or something similar. Do you see how the active voice is still better just by being less wordy?

In most writing, you want to avoid passive construction as much as possible. Sometimes it is unavoidable but wherever you can revise it out of your sentences, your writing will be stronger for it overall.

Examples of Passive Infinitives

Understanding passive voice leads to easy identification of passive infinitives, as they are passive constructions using infinitive verbs. Examples:

• Everybody wanted to be told over and over again the things which had happened to her.
• The answer to that mystery was not likely to be revealed to me anytime soon.
• "Hold your tongue," said the King, very crossly. "I intend you to behave prettily to her. So now go and make yourself fit to be seen, as I am going to take you to visit her."
• He had come home feeling heroic, and ready to be rewarded. Playing in the big leagues again had rejuvenated him.
• The foundation of imitation among us comes from the desire to be transported out of ourselves.

Double Passives

Double passives are those phrases that contain two connected passive verbs, the second of which is a passive infinitive. For example, examine "The seasonal work was needed to be done by temporary employees." 

To transform the example to active voice, recast the sentence by inserting a subject and rearranging to make "The company needed temporary employees to do the seasonal work."

Adjectives With Passive Infinitives

You may also see adjectives inserted into a passive infinitive construction, such as fit, ready, eager, and easy. Check out these examples from "A History of the English Language:"

"With adjectives, passive infinitives are generally only used in PDE [present-day English] when an active infinitive may lead to ambiguity, as in the case of likely or fit, cf. you are not fit to be seen...Another adjective which has retained the option of using a passive infinitive is ready. Thus the well-known ambiguity of (113) can be avoided by using the variant in (114):

• (113) The lamb is ready to eat.
• (114) The lamb is ready to be eaten."

Olga Fischer and Wim van der Wurff, "Syntax."

"Other adjectives still allowing the passive infinitive tend to be like ready in that they can occur in both the easy-to-please construction...and the eager-to-please construction (where it is to be interpreted as the subject of the infinitive)."

Sources

Baugh, Albert C. "A History of the English Language." 6th New edition edition, Routledge, August 17, 2012.

Burnett, Frances Hodgson. "A Little Princess." Paperback, CreateSpace Independent Publishing Platform, January 24, 2019.

Fischer, Olga. "A Brief History of English Syntax." Hendrik De Smet, Wim van der Wurff, Cambridge University Press, July 17, 2017.

Hartwick, Cynthia. "Ladies with Prospects: A Novel." Paperback, 1st edition, Berkley Trade, April 6, 2004.

Lang, Andrew. "The Red Fairy Book." Dover Children's Classics, H. J. Ford (Illustrator), Lancelot Speed (Illustrator), Paperback, Reprint. edition, Dover Publications, June 1, 1966.

Phillips, Terry. "Murder at the Altar." Paperback, Hye Books, February 1, 2008.

Rousseau, Jean-Jacques. "Emile: Or On Education." Paperback, Independently published, April 16, 2019.