I swear to do it tomorrow! is standard.

What about the prefect infinitive and gerunds?

1 I swear to have done it yesterday! - CORRECT?

2 I swear doing it yesterday! - CORRECT?

3 I swear having done it yesterday! - CORRECT?


2 Answers 2


swear is basically a performative verb. That page explains them in more detail. performative verbs in the form of a declaration

More idiomatic for this performative meaning:

  • I swear I will do it tomorrow. [I raise my hand]

  • I swear I did it yesterday. [I raise my hand]

  • I swear (to you) that I have done it in the past. [undefined past, not performative]

The three samples in the question are basically ungrammatical.

"swear to" can be followed by a noun/pronoun:

I swore to him that I had done that.

OR, with a verb after to

  • I swear to leave within the hour. [present]
  • I swore to leave within the hour. [past, no change after to]

No past infinitive after to:
I swore to having left at 6 o'clock. [no past infinitive]
I will swear to having left at 6 o'clock.

  • If they are ungrammatical how can you explain these examples taken from different books? 1 Will you swear to have seen one gun? 2 Do you swear doing any work for Charles? 3 This concession was not pursued on redirect examination and , accordingly , the record was left with testimony by a witness about an event which had assertedly preceded execution of a contract that he could not swear having seen. Are they also ungrammatical?
    – user1425
    Dec 12, 2022 at 15:00
  • 3
    @user1425 You are now changing course. The ones in your question do not work. You can't expect me to cover every single instance. That said, Your 1) there is similar to my last one. I do not accept 2) or 3) Do you swear to doing any work for Charles. 3) that he could not swear to having seen.
    – Lambie
    Dec 12, 2022 at 15:13
  • 1
    @user1425 I swear [something] is a performative verb: I swear I will do it. I swear I have done it. It's raising your hand in a declarative statement. It's similar to promise, same thing. To swear to something is not performative. So, you can say: Will you swear to having seen a gun? Or: Will you swear to seeing a gun. Versus: I swear I saw it yesterday (performative). The difference is performative versus non-performative. "swear to something" is asking a person if they will state it as a performative.
    – Lambie
    Dec 12, 2022 at 15:50
  • 1
    "I know her to have been a good wife" is past tense. To wit, "I know her to have been a good wife but she isn't one any longer." Generally we say: I swear I saw him or I swear I have seen him before (performatives). And I will swear to that in court. [not performative]. to have seen is also past tense.
    – Lambie
    Dec 12, 2022 at 16:23
  • 1
    @user1425 Unfortunately, you are mistaken. I know her [in the present, I have that knowledge] to have been a good wife [in the past]. I know her to be a good wife = Present Tense. It is very difficult to help someone who seems not to want to accept an obvious statement. How you claim that "to have been x" is not past tense, is beyond me. I even gave you a sentence contrasting to have been and is no longer.
    – Lambie
    Dec 12, 2022 at 16:36

There are two different meanings of swear, that subcategorize for different grammatical arguments.

Swear meaning "strongly promise" takes either a to infinitive clause, or a finite that clause with explicit expression of intention:

I swear to give up smoking = I swear that I will give up smoking.

Swear meaning "strongly assert or affirm" normally takes a finite that clause, but can also take to with an -ing clause. The latter is rather literary or old-fashioned.

Your sample sentence has the first meaning, and so is as you say standard with the to infinitive.

Your three numbered sentences are all in the past, so cannot have the first meaning, and must have the second. None of them satisfy the conditions I've mentioned above, so all three are ungrammatical.

  • Upvoted. But still I think they are not ungrammatical as such but they represent older English. After all, I didn't make them up but copied from books.
    – user1425
    Dec 12, 2022 at 17:59
  • The Cretan , then , claims to have met a man who swears to have seen and helped Odysseus recently
    – user1425
    Dec 12, 2022 at 18:08
  • I won't argue that, @user1425. I was wondering whether to describe them as ungrammatical or merely unidiomatic.
    – Colin Fine
    Dec 12, 2022 at 23:26

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .