# Past Conditional

I would like to write about a speculative situation in the past and a possible result in the past. For example,

(1) If A did X, Y occurred.

(2) If A did X, Y could have occurred.

(3) If A did X, Y would have occurred.

(4) If A did X, Y might have occurred.

(5) If A did X, Y should have occurred.

We have no idea whether A did X or not, so I think example (3) is not appropriate. I would use example (1), if I am pretty certain that under this condition (If A did X), the main clause is true (Y occurred). But this is not the case. Even if the condition is true, there are multiple possibilities and Y is just one of them. So I can't use example (5). Do you think example (2) or (4) could convey the meaning I would like to express?

I would go with #2.

If A did... you don't know what A did or didn't do.

But if A had done X, then Y could have occurred.

Not knowing if Y occurred or not in the past means it may or may not have happened.

Even if we knew now that Y did happen, how do you know that it was a result of anything A did or did not do?

Maybe B did something else entirely, causing Y to have occurred.

Once again, we'll never know.

• Just to clarify, do you think #2 is the best way to express the uncertainty of causal relationship regarding a past event? Or is there any better way to express this? Thank you very much for your help!
– hkim
May 18, 2020 at 0:15
• @ hkim, I believe that number two fits. I will agree that might have happened runs a close second. May 18, 2020 at 0:18
• Thank you so much for your clarification!
– hkim
May 18, 2020 at 0:19
• @ hkim One last thing - if B did the same thing as A at the same moment as A, Y might have occurred.... :) May 18, 2020 at 0:22