2. MODALS FOR SPECULATIONS AND
INFERENCES ABOUT PAST SITUATIONS

3. MODALS FOR SPECULATIONS AND INFERENCES
ABOUT PAST SITUATIONS
When we make MUST
deductions or MIGHT / MIGHT NOT
inferences about past (MIGHTN'T)
situations, we can use
the same modals we MAY / MAY NOT
used for speculations COULD / COULD NOT
about the present, with (COULDN'T)
the same meaning: CAN'T
•

4. The difference is in the structure:
PRESENT Modal + Base form of the
verb
PAST MODAL + HAVE + PAST
PARTICIPLE

5. PRESENT
Amelia can’t be alive (now).
She disappeared in 1937.
PAST
Amelia’s plane might have
had technical problems.

6. Remember:
To make deductions or inferences in the past
use:
Must or Mustn’t + Have +
When you have evidence
Past Participle
Can’t + Have + Past When something is unlikely
Participle to have happened
May (may not / Might
(mightn’t) / Could + Have + When you are not so sure
Past Participle about something

7. Atlantis mustn’t have existed. There is no
evidence about it .

8. The crew from Mary Celeste might have
been abducted.

9. The drawing could have been made
by extraterrestrials.

10. Now click on the link to do some
practice exercise about these kinds of
modals.