Speculation & Deduction: Present and Past
At B2 you speculate and deduce about both the present and the past, and you add expressions beyond modals. The degree of certainty — from sure to merely possible —…
At B2 you speculate and deduce about both the present and the past, and you add expressions beyond modals. The degree of certainty — from sure to merely possible — is shown by your choice of modal.
Present speculation
| Certainty | Modal | Example |
|---|---|---|
| sure it’s true | must | She must be exhausted. |
| possible | may / might / could | He might be at home. |
| sure it’s not true | can’t / couldn’t | That can’t be right. |
Past speculation
| Certainty | Form | Example |
|---|---|---|
| sure it happened | must have + pp | She must have left. |
| possible | may/might/could have + pp | He might have forgotten. |
| sure it didn’t | can’t/couldn’t have + pp | They can’t have finished. |
Continuous deductions tooYou can speculate about actions in progress: present — “She must be working late”; past — “He must have been sleeping.” Use modal + be + -ing (present) or modal + have been + -ing (past). Beyond modals, expressions like be bound to, be likely to, and I bet also express probability.
Examples from EduCareer
- Aisha isn’t answering — she must be in class.
- Omar did badly; he can’t have revised much.
- The lights are off; they may have gone home.
Tutor tip for Arabic speakersFor a confident negative guess, the opposite of must is can’t — never “mustn’t.” Present: “He can’t be serious.” Past: “He can’t have been serious.” Keep the structure modal + have + past participle together for all past deductions.
Common mistakes
- He mustn’t be home (deduction). → He can’t be home.
- She must have went. → She must have gone.
- They can’t finished so fast. → They can’t have finished so fast.
Practise with the 20 questions below.
Check your understanding
Answer the questions below. You will see instantly if you are right.
1."The lights are on. Someone ___ be home."
sure → must.
2."He failed badly — he ___ revised much."
sure it didn't happen → can't have.
3."She's not replying; she ___ be busy."
possible → might.
4."They started 2 minutes ago; they ___ finished."
impossible so soon → can't have.
5.Past deduction structure:
modal + have + past participle.
6.Opposite of 'must be' (deduction):
can't be.
7."The ground's wet; it ___ rained."
evidence → must have.
8."She ___ be working late — her car's still here."
present continuous deduction → must be working.
9.Which is correct?
past participle 'gone'.
10."He ___ have been sleeping when I knocked."
past continuous deduction → must have been + -ing.
11."You ___ be joking! That's impossible."
strong reaction → must.
12."He ___ have left already — his coat is gone."
evidence → must have.
13."I'm not certain, but they ___ have missed the train."
uncertain → may have.
14.Which expresses probability (not a modal)?
be likely to = probability.
15."That ___ be Sara — she's abroad this week."
sure not → can't.
16."The exam was hard; she ___ have found it easy."
sure not → can't have.
17."He looks pale — he ___ be feeling well."
sure not → can't be.
18."They're laughing; the news ___ be good."
evidence → must.
19."I ___ have seen her there — maybe I'm wrong."
uncertain memory → might have.
20."With his skill, he ___ to win." (probability expression)
be bound to = near-certain.
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