E.g. First one is:

The incident could have happened.

And the second one is:

The incident could have been happened.

What is the difference in terms of their meaning? Or is there any grammatical mistake?

  • Your second version is not syntactically valid. In certain contexts you could validly say The incident could have been happening, but pragmatically those contexts would have to include (explicitly or implicitly) a reference to a specific point in past time and/or to a specific duration. For example, The pipe could have been leaking for months before we noticed anything, which includes both (duration = months, point in time = when we became aware). Commented Feb 6, 2019 at 13:39
  • 1
    Possible duplicate of "would not have been happened" vs "would have not been happened" Commented Feb 6, 2019 at 14:10
  • "have been happened" is a Passive-Voice while 'happen' is an intransitive verb, that therefore is invalid. Commented Feb 6, 2019 at 14:11

1 Answer 1


There is no difference here. Both are "could have". "Could have" is a modal conditional perfect construction ("would have" being the conditional perfect) when followed by a past participle.

Thus, with the part participle "happened", you get "the incident could have happened".

"Could have been" is just the same, but with the past participle of "to be". Thus, it cannot be followed by any old past participle - your second example is wrong. Not every verb can be used there. Caused, avoided or averted could, in this case. These are constructions where the 'incident' is acting as an object to those verbs, but rendered in the passive voice and thus grammatically looking like a subject for an auxiliary verb. If the verb is intransitive, or cannot meaningfully take the earlier noun as an object, you can't use such a construction. In the first case, that's because intransitives cannot be rendered passive; in the second, it's just because it would make no sense semantically.

It can be followed by an adjective - "the incident could have been serious" - by a progressive participle - "the incident could have been happening" - or by some noun phrases, particularly those that start with an article - "the incident could have been the worst ever".

  • OP's second example is indeed invalid, but it's not really because "it cannot be followed by a past participle" - consider, for example, The incident could have been avoided. Commented Feb 6, 2019 at 14:10
  • @FumbleFingers Fair point, editing.
    – SamBC
    Commented Feb 6, 2019 at 14:11
  • I think the key point here is happen is intransitive and cannot be cast in the passive Commented Feb 6, 2019 at 14:12
  • Apart from the mention of passive, that's what I wrote before I saw your follow-up comment. I'll add that.
    – SamBC
    Commented Feb 6, 2019 at 14:16
  • It's a bit of a head-scratcher when I think about it too long. I can just about see "syntactic validity" in, say, My thoughts on this matter are affected equally by two very different "types of incident" that I can call to mind - the happened ones and the imagined ones. That's to say it's tricky / marginal, but not totally ridiculous to construct contexts where that past tense intransitive verb could be used "passively / adjectivally". Commented Feb 6, 2019 at 14:37

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