Using Perfect Infinitives with Modal Verbs

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The structure “have + past participle” is called a perfect infinitive.

In this lesson, we will learn about the combination between modal verb and perfect infinitive.

Contents

Form:

MODAL + HAVE + PAST PARTICIPLE

Usage:

Express deduction, a logical conclusion, probability

Express negative deduction (impossibility in the past)

Express past reference about something that was not carried out

You could have done it. (You didn’t do it)
She could have called the doctor early in the morning. (She didn’t call the doctor)

Express the possibility that an action took place in the past

The little girl may have lost the key. (It is possible that she lost the key.)

Express a past possibility

Express an unnecessary action, which was, nevertheless, performed

I needn’t have knocked at the door since, in this way, I awoke the baby. (But I knocked)
You needn’t have bought the flowers.

Indicate that the past obligation was not fulfilled or carried out

You should have locked the door before leaving the house. (But you didn’t lock it.)

Express an unfulfilled duty or obligation

Paul ought to have waited until the lights were green before he crossed the street. (But he didn’t wait.)

The third conditional

I would have gone to university if my parents had had more money. (The speaker didn’t go to university.)

Perfect Infinitives with Modal Verbs | Image

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