Grammar‎ > ‎Modals and Modal Verbs‎ > ‎

Modals for Degrees of Certainty in the Past

Modals can be used to show a degree of certainty.

Must have been, may have been, might have been, and could have been are used to show a degree of certainty in the past. 

Couldn't have been, can't have (been), must not have (been), may not have (been), and might not have (been) are negative.


Degrees of certainty in the past

To show degrees of certainty in the past we use modal + present perfect.

Since the verb that follows a modal is in simple form the structure is: modal + have + verb in past participle.

If you are very confident then use the simple past.

  • The party was great.

If you are not completely certain then use must + present perfect.

  • The party must have been great.

If you are around 50% certain use may + present perfect.

  • The party may have been great.

If you are not very sure at all use might or could + present perfect . These show that you doubt it.

  • The party might have been great.
  • The party could have been great.

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