Modals of Deduction/Probability
What Is It?
Modals of Deduction/Probability refers to modal verbs used to judge how likely something is.
B1-B2 reference topic in Modal and Hypothetical Structures.
Why Use It?
- Express certainty, probability, and impossibility.
- Make careful guesses from evidence.
- Talk about present and past deductions.
Formation and Patterns
| Use | Pattern | Example |
|---|---|---|
| Present certainty | must + base verb | She must be tired. |
| Present impossibility | can't/couldn't + base verb | That can't be right. |
| Past deduction | must/may/might/can't + have + V3 | He must have forgotten. |
Common Mistakes
- Using mustn't for logical impossibility; use can't.
- Forgetting have in past deductions.
- Treating might as certainty.
Exceptions & Nuances
- Could have can mean possibility or missed opportunity; context matters.