I learned that I should use have + p.p. in the sentence below.

The game starts in 5 minutes. If I had taken that train, I could have been on time.

And I think there can be sentences like this:

I am looking for my key. If I had not forgot my glasses, I might be able to find it.

If the second sentences are correct, why should I use "have + p.p." in the first sentences, where you haven't been late yet, and which is about future? Or the second one is not correct?

3 Answers 3


Both sentences are correct.

The past result clause in the first sentence, "I could have been on time", means, "I made myself late by not taking that train" in the past. The sentence would have the same meaning if reworded to, "... I could be on time". This would mean, "I might still be on time right now if I had taken that train."

That alone might answer your question.

The second sentence has a present result (may be able to find my key). Because the result is in the present --I'm looking for my key right now-- using "might" is correct. It means, "I can't find my key because I didn't bring my glasses."

Very interesting problem!


First, note that "forgot" is the preterite and "forgotten" is the past participle.

The second sentence is on the edge of plausibility to my intuition. I strongly prefer "I might have been able to find it" — and that would of course resolve your question.

However, there is a way to interpret the sentence as written. If "might have been able" suggests that the speaker has already concluded that they won't find their glasses on this occasion, then "might be able" expresses doubt as to whether glasses would help in general. It suggests: "If I had my glasses, we would find out whether I was able to find my key with their help."

  • Thank you so much for your help! So, "I might be able to find my key if I had not forgotten my glasses" could mean "I am not sure whether I was able to find my key in an occasion where I didn't forget my glasses"?
    – Nigutumok
    Aug 24, 2022 at 5:15
  • 1
    @Nigutumok It means "If I had my glasses, I might be able to find my key." The logic lies in equating "If I hadn't forgotten my glasses" and "If I had my glasses". Aug 24, 2022 at 15:29

Firstly, the initial sentence is grammaticaly incorrect. The game hasn't started yet; it would be correct to use your sentence if the game started and you comment on the past. Like this:

"I was late yesterday. When I got there, the game had already started; I wouldn't have been late if I had taken a taxi."

From British Council Learn English Web site

The third conditional is used to imagine a different past. We imagine a change in a past situation and the different result of that change.

Your second sentence is fine, except the verb form (forgotten, it should be).

From the BBC Towards Advanced Masterclass

Past hypothetical situation with a present hypothetical result


If I had taken programming at school, I'd have a job at Google now.

If I hadn't eaten so much cake, I wouldn't feel so sick.

Finally, once a teacher said "Conditionals are all about lawlessness."

  • Thank you so much for the detailed answer! Then, should my first sentence be like this? "If I had taken that train, I could be on time." I have already asked on a different website whether "have + p.p." should be used or not, and I got answers that I should say "I could have been on time."
    – Nigutumok
    Aug 24, 2022 at 5:40
  • @Nigutumok The answers are naturally varied when it's the conditionals. I provided you an answer from an ESL student perspective as I observed that many natives, even teachers, don't care much about the conditionals and related rules. So, the 2nd conditional would fit your first sentence. 'The game starts in 5 minutes; If I took that train, I could/would/might be on time.'
    – user138449
    Aug 24, 2022 at 12:13
  • 6
    I think the first sentence is OK. It's possible to be not on time even before the deadline. Being on time includes the meaning of being in a position to arrive on time, and vice versa. Like, if the game starts in 5 minutes, but you're 15 minutes away, you can say, "I'm not on time", though it would be more natural to say, "I'm late".
    – gotube
    Aug 24, 2022 at 14:10
  • I agree, you can consider yourself late before an event starts if you have no way to get there in the remaining time.
    – Hellion
    Aug 24, 2022 at 15:24

You must log in to answer this question.

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