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Unit 08
Modals of Speculation
probability in context
Speculating with Modals
Modal verbs of probability let us express how certain or uncertain we are about situations — in the present, past, or future. They appear in conversation, storytelling, and formal writing.
Degrees of Certainty
| Level | Modal | Example | Meaning |
|---|---|---|---|
| ~100% positive | must | He must be the manager — he's giving orders. | Logical conclusion from evidence |
| ~100% negative | can't / couldn't | She can't be home — her car isn't here. | Logical impossibility |
| ~50–70% | should | The parcel should arrive today. | Expected |
| ~40% | might / may / could | They might be out for lunch. | Uncertain possibility |
Present Probability
Modal + base verb for current situations.
- He must be busy — he's not answering.
- She can't be serious!
- They might be at work right now.
- This could be a mistake.
Past Probability
Modal + have + past participle for past situations.
| Modal | Meaning | Example |
|---|---|---|
| must have | ~95% sure it happened | He must have forgotten the meeting. |
| can't have | ~95% sure it didn't happen | She can't have seen us. |
| might / could have | ~40% possibility | They might have left early. |
Speculation in Conversation
In natural dialogue, modals of speculation show logical reasoning or emotional reaction.
| Situation | Response using modal |
|---|---|
| "Where's Tom?" | "He must be in a meeting — his phone's off." |
| "I can't find my wallet!" | "You might have left it in the car." |
| "The lights were on when I arrived." | "Someone must have been here." |
| "Did you hear that noise?" | "It could have been the wind." |
Speculation in Narrative
Writers use modals to show inference, perspective, or suspense:
- The door was open. Someone must have forgotten to lock it.
- The streets were empty — they might have left early.
- It's getting dark. They must be close now.
- She can't be serious about quitting.
Continuous Speculation & Strong Alternatives
| Form | Example | Meaning |
|---|---|---|
| modal + be + -ing | She must be working late. | in progress now |
| modal + have been + -ing | His eyes are red. He must have been crying. | in progress in the past |
| may well / might well / could well | Prices may well rise again. | quite likely |
| be bound to / be sure to | It's bound to rain — it always does. | almost certain (future) |
| be (un)likely to | He's unlikely to agree. | probable / improbable |
Annotated Examples
Subject
Verb
Auxiliary
Object
Adjective
Adverb
Preposition
Hover over any word to see its role.
subjectHeauxiliarymust beadjectivetired—he hasn't slept in days.
↳ Present deduction — must + base verb.
subjectSheauxiliarycan't haveverbknown—she just arrived.
↳ Past impossibility — can't have + past participle.
subjectTheyauxiliarymight haveverbleftadverbearly.
↳ Past possibility — might have + past participle.
Common Mistakes
He must to be tired.
→
He must be tired.
No "to" after modal verbs.
She can't have saw you.
→
She can't have seen you.
Use the past participle: seen (not saw).
They might has left.
→
They might have left.
Always "have" (not "has") after a modal.
He must be left early.
→
He must have left early.
Past speculation: must have + past participle.
It can't to be true.
→
It can't be true.
No "to" after modal verbs.
He must sleep now — the lights are off.
→
He must be sleeping now.
Action in progress now → must be + -ing.
She is bound to forgetting.
→
She is bound to forget.
bound to + base verb.