Modal perfects in English B2
Use modal + have + past participle to infer, criticise or consider possibilities about completed events.
Make past deductions with different degrees of certainty.
Express criticism or regret with should have.
Separate strong conclusions, open possibilities and logical impossibility.
A certainty scale for past events
Modal perfects do not change the event; they reveal the speaker’s interpretation of it. Must have presents the evidence as highly convincing, while might have keeps competing explanations open.
Can’t have is the negative end of the deduction scale: the available facts make the proposed explanation impossible.
| Assessment | Form |
|---|---|
| almost certain | must have |
| possible | might/may/could have |
| impossible | can’t/couldn’t have |
Why should have is not a deduction
Should have evaluates an action that did not happen, or did not happen as expected. You should have checked the figures normally implies that the figures were not checked and a negative consequence followed.
Context decides whether the tone sounds like advice, disappointment, criticism or regret.
Evidence controls the modal
Begin with the evidence, not the grammar. A locked door may support can’t have entered; a missing coat may support must have left; uncertainty about a route may call for might have taken.
A responsible speaker selects the strength of the modal in proportion to the strength of the evidence.
Pronunciation does not change spelling
In rapid speech, have is often reduced, but it remains have in writing. Could of and should of are spelling errors caused by the sound of the contractions could’ve and should’ve.
The grammatical sequence is always modal + have + past participle.