Modal verbs – speculation & deduction
One of the functions of modal verbs is to express speculation.
Depending on the degree of probability of our deduction, we use different verbs.
Therefore:
- The verb “must” is an almost absolute certainty:
The phone’s ringing. It must be Paul.
- Its opposite is “can’t” and “couldn’t”, meaning that a situation does not happen.
The phone’s ringing, but it can’t be Paul. He’s still at work.
- The verbs “may/might/could” are used to express possibilities, but could is a little weaker in its expression:
The phone’s ringing. It may be Paul.
The phone’s ringing. It might be Paul.
The phone’s ringing. It could be Paul.
| probability | verb | example |
|---|---|---|
| 0% | Simple Present (negative sentence) | He doesn’t know. |
| unlikely | can’t/ couldn’t | He can’t know. |
| 50% probability | could | He could know. |
| quite likely | may/ might | He may know. |
| very likely | must | He must know. |
| 100% probability | Simple Present | He knows. |