It is written in my grammar textbook that the past form of “might” is “might have + past participle”, for example:

Present: “I might go to the party.”

Past: “You might have left your keys in the car.”

I found the following in an official document from ETS:

And even though some members tried to warn the rest of the group that the project was moving in directions that might not work, they were basically ignored by other group members.”

I think "might not work" should be in the past form, I mean: “might not have worked”, because it is all about past time. Am I right? If not, why?

  • [fyi, it's better to say: My grammar book states a, b or c. Try to avoid: It is written in my grammar book. X is given in my grammar book.]
    – Lambie
    Aug 15, 2020 at 18:51

3 Answers 3


The example sentence could be changed as you suggest (might not have worked), and that would not be wrong. But it's also correct as it stands. It is an example of "future in the past".
Cambridge "future-in-the-past"

When we talk about the past, we sometimes want to refer to something which was in the future at the time we were speaking. We use past verb forms to do this:

(emphasis added)

That and other sites use examples with the word "would", but just as "would" is the past tense of "will", "might" is the past tense of "may". The only difference is that "will" expresses certainty, and "may" expresses a possibility.

In that past time, one might have said "the group is moving in directions that may not work".
Expressing it as future-in-the-past, it is correct as "the group was moving in directions that might not work".


This is really about the timing.

If the project is still underway with its success uncertain, might not work is fine. The project still might not work out because of the directions it is taking.

If the project has failed and people are trying to establish why it failed, might not have worked is more appropriate. They are looking back to see what the problem had been - whether the directions taken at the time led to its failure.

There is no right answer to this question. The context is what points to the more appropriate tense.


It is too simplistic to say "might have"+past participle is the past of "might".

It's true that "Might have"+past participle is used when we are discussing past events (completed events): e.g. I thought I might have forgotten my key, but then I found it in my pocket or He might have kissed her if he had been brave enough or She might have been the true author of Shakespeare's plays, according to new research.

But "might" is invariant in the past when backshifting the tense of a sentence in order to report speech or past thoughts, etc.

Direct speech: "I may go," she said or "I might go," she said.

Indirect speech: She said that she might go. ("May" usually backshifts to "might". "Might" is invariant when backshifting.)

I think I may go. / I think I might go.

Next day: Yesterday I thought I might go, but in the end I didn't.

It's correct to say that the doubters warned that the project might not work. Contrary to one of the other answers, this observation remains valid (and correct grammar) regardless of whether the project is ongoing and regardless of whether it was in fact completed. For example, it would be perfectly legitimate to write in a history of the Second World War that "people feared that Hitler might invade Britain". (If you wrote "people feared that Hitler might have invaded Britain", that would have a different meaning: it would imply that, at the time of their fear, they feared that he actually might already have invaded. You only use might+perfect where, at the time of the statement being made or possibility being felt, the possibility was already either fulfilled or not fulfilled - even if you don't know which - as in She might have written me a letter, but if she has, I haven't received it yet.)

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