I want to ask if the use of "would have + verb in past participle" is appropriate in a paper. What is the correct way of expressing a hypothetical outcome when describing past events? I may be wrong, but I think I've never seen "would have + past participle" used in a scientific work.

Example: "We decided not to perform this action, because it would have required ...". Can "would have required" be replaced with "would require" in this sentence?

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    It’s not past tense. Commented Jun 23 at 6:29
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    What are the …? If it is some time specific condition ("to have more manpower than we did") the construct not only seems okay, but absolutely correct. Commented Jun 23 at 6:48
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    @pvpvpvpv If you follow the traditional sequence of tenses in English, the simple past in the main clause ("We decided not to perform this action") actually forces you to use a perfect conditional instead of the present conditional in the dependent clause ("because it would have required [whatever]" instead of "because it would require [whatever]"). Commented Jun 23 at 16:12
  • Thank you all. @user3840170, you are right, my mistake. I've corrected it.
    – pvpvpvpv
    Commented Jun 23 at 16:28
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    Seems like more of an English SE question to me. Commented Jun 23 at 17:38

3 Answers 3


Don’t overthink it. Either is fine and nobody will (would) notice. It is perfectly clear either way.


Tl; dr: In most cases the past tense is not wrong. The present tense is only correct if the statement is indeed still true.

The somewhat subtle difference is that the simple "would require" indicates that this requirement or possible route not chosen is still existing or possible at the time of speaking. For example, imagine a press conference about an ongoing hostage situation:

We decided against a police intervention because the risk for the hostages would be unacceptably high.

At the time of speaking, the risk still would be too high. One could use the past tense here as well, avoiding a statement about the present:

We decided against an intervention when the group entered the building because the risk for the hostages would have been unacceptably high. But our snipers are still in place and we are monitoring the situation closely.

But the present tense cannot be used for requirements or possibilities which do not exist any longer. In a report about the same situation a year later, one might read:

We decided against a police intervention at this point because the risk for the hostages would have been unacceptably high.

In this case, the present tense would be wrong because the risk does no longer exist.

I suppose that in scientific articles the present tense is often adequate because the requirement is still there:

We did not check for specific compounds in the samples because the small concentrations would require specialized analytical equipment.

They still do.

  • There is a chance that the specialised equipment is no longer an issue because they acquired it in the meantime, or analysis techniques evolved. Would it be appropriate to use "would have required" simply to avoid guessing the future situation? Commented Jun 24 at 6:06
  • @MisterMiyagi Yes, I'd say so: The past tense here does not necessarily make a statement about the present. "He was not at home when the crime happened" is indifferent about whether he's at home now. The opposite inference, where the present tense is understood to make a statement about the past as well, is only from context: "Why didn't you pick up?" -- "I told you I'm on a business trip!" vs. "Why do I get intruder alerts suddenly, have you gone to our summer home?" -- "Yes, I am in the house" [but wasn't before]. Commented Jun 24 at 6:20
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    @MisterMiyagi Indeed, if there is a chance that the statement about the past is not true in the present, I'd say it is much better to use the past tense. The present tense clearly implies that it is still true. Commented Jun 24 at 6:23

I have been stumbling upon this thought here and there. After a couple of thoughts, I decided to use the present tense, because it is shorter in length.

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