Speculation and deduction: Modal verbs and expressions — Explanation

Practice B2 speculation and deduction using modal verbs. Interactive exercises, clear explanations, and real examples to improve accuracy fast.

Speculation and Deduction Exercises

Often, when we don’t know something for sure we guess or deduce. This is often achieved in English by means of modal verbs and some expressions. At B2 level you should be able to use these forms correctly to speak about the present and the past.

What’s Speculation and Deduction?

• Speculation = guessing without full information
• Deduction = making a logical conclusion based on evidence

Example:

• She isn’t answering her phone. She might be sleeping. (speculation)
• The lights are off. They must be out. (deduction)

Modal Verbs for Present Speculation

We use modal + base verb to talk about the present.

Common structures:

• must + verb → strong certainty
• might / may / could + verb → possibility
• can’t + verb → strong impossibility

Examples:

• He must be tired after working all day.
• They might live near here.
• She can’t be at home – I just saw her outside.

A tip:
“Must” is when you’re really sure.
"Can't" means something is logically impossible.

Modal Verbs of Speculation (Past)

For guessing about the past we use:

• must have + past participle
• might / may / could have + past participle
• can’t have + past participle

Examples:

• He must have forgotten the meeting.
• They might have taken the wrong train.
• She can’t have left already – her bag is still here.

Hint:
Use these forms to think about what probably happened in the past.

Other Helpful Phrases

You should also be aware of alternative ways to speculate at B2 level:

Common expressions:

• It looks like…
• It seems (that)…
• I suppose…
• I guess…
• There’s a chance that…

Examples:

• It looks like they’re closed.
• It seems that he’s upset.
• I guess she forgot about the appointment.

Levels of Certainty Comparisons

It’s important how strong your statement is:

Expression	Certainty Level
must	very strong (≈ 90–100%)
might / may / could	medium (≈ 30–70%)
can’t	very strong negative (≈ 0%)

Example:

• He must be at work. (very sure)
• He might be at work. (not sure)
• He can’t be at work. (sure he isn’t)

Final Tip

To increase your fluency, combine:

• modal verbs
• time references (present vs past)
• real-life situations

The more you do this, the more natural will sound your speculation and deduction.