Explanation
Exercises
Modal Deduction & Probability

Lesson focus

Degrees of certainty, deduction, possibility and expectation with modal verbs in present and future contexts

Advanced aim: Express graded certainty and evidential reasoning; the advanced skill is calibrating force rather than memorising modal labels.

Strong positive deduction

Use must for a strong logical conclusion based on available evidence.

  • Example: The lights are on and her car is outside; she must be at home.
  • In another context: Separate scenario: The lights are on and her car is outside; she must be at home.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Strong negative deduction

Use can't for a strong conclusion that something is impossible or highly unlikely.

  • Example: That can't be the final version; several sections are still missing.
  • In another context: Follow-up case: That can't be the final version; several sections are still missing.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Neutral possibility

May, might and could can express specific possibility. Their relative strength is highly context-dependent, so avoid treating them as a fixed probability scale.

  • Example: The delay might be caused by a problem at the distribution centre.
  • In another context: The approval delay might be caused by a problem at the dispatch depot.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Expected outcome

Should can express an expectation based on normal circumstances.

  • Example: The parcel should arrive by lunchtime if traffic is normal.
  • In another context: The sample shipment should arrive by lunchtime if traffic is normal.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Assumptive will

Will can express a confident assumption about a present situation, especially in conversation.

  • Example: That'll be Marcus calling; he said he'd ring around six.
  • In another context: That'll be Daniel calling; he said he'd ring around six.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

General possibility with can

Can is common for general or theoretical possibility rather than one specific uncertain event.

  • Example: Even experienced negotiators can misread the mood of a room.
  • In another context: Follow-up case: Even experienced negotiators can misread the mood of a room.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Specific possibility with could

Could can describe a specific possible explanation or outcome.

  • Example: The error could be the result of an outdated data feed.
  • In another context: The reporting inconsistency could be the result of an outdated information feed.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Probability phrase

May well strengthens may and suggests that something is quite possible.

  • Example: The policy may well create more problems than it solves.
  • In another context: The disclosure procedure may well create more problems than it solves.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Remote possibility

Might can signal a more tentative possibility when the speaker wants to avoid sounding certain.

  • Example: There might be another explanation that we haven't considered.
  • In another context: Separate scenario: There might be another explanation that we haven't considered.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

Inference from absence

Can't normally expresses negative deduction, not prohibition, when the context is evidential.

  • Example: He can't be in the office; his access card hasn't been used today.
  • In another context: He can't be in the temporary workspace; his access card hasn't been used today.

C1 focus: Choose this form for the intended meaning and discourse effect; nearby alternatives may be grammatical but can change viewpoint, scope, time reference or register.

C1 takeaway

Do not ask only “Which form is grammatically possible?” Ask what the speaker is presenting as background or foreground, completed or ongoing, certain or tentative, generic or specific, neutral or emphatic. Advanced grammar is the control of those choices.

Exercises:
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Degrees of certainty, deduction, possibility and expectation with modal verbs in present and future contexts

1
Complete the sentence with the form that presents the conclusion as very strong because several pieces of evidence point the same way: Her laptop is connected to the office network and her coat is on the chair; she somewhere in the building. (be)
2
Complete the sentence with the form that presents the proposed explanation as incompatible with the evidence: That the signed contract; the signature page is missing. (be)
3
Give one natural modal completion that presents the cause as a genuine possibility rather than a firm conclusion: The intermittent outage by interference from nearby equipment. (cause)
4
Complete the sentence so that the arrival is presented as the expected outcome if normal conditions continue: The courier left the depot on schedule, so the parcel before noon unless traffic deteriorates. (arrive)
5
Complete the conversational response using the form that makes a confident assumption based on what was already expected: The doorbell's gone. Mina; she said she'd come by at seven. (that / be)
6
Complete the general statement with the modal that presents this as a recurring theoretical possibility, not one specific uncertain event: Even a small sampling bias the apparent trend in a large dataset. (distort)
7
Complete the sentence so that the explanation is kept deliberately tentative and is presented as only one possibility among several: One explanation we have not ruled out a timing fault in the sensor array. (be)
8
Complete the sentence with the phrase that means the outcome is quite possible without presenting it as certain: Removing the review stage more bottlenecks than it removes. (create)
9
Complete the sentence so that the speaker leaves open a tentative possibility despite the apparently negative evidence: The lab is dark, but someone inside; the night team sometimes works with the blinds closed. (be)
10
Complete the inference using the strongest negative conclusion justified by the access records: Nadia in the secure suite: the system shows that her badge was deactivated yesterday. (be)

Degrees of certainty, deduction, possibility and expectation with modal verbs in present and future contexts

1
Three independent clues all point to the same conclusion. Choose the strongest evidence-based deduction: Her bicycle is outside, her desk lamp is on and she answered an internal chat message two minutes ago; she in the office.
2
Choose the form that expresses impossibility inferred from evidence, not prohibition: This the complete submission; the mandatory annex is not attached.
3
Only one of the options keeps this explanation genuinely possible without making it certain or impossible: The fluctuation by a calibration error, but we need more tests before drawing a conclusion.
4
Choose the form that presents the arrival as normally expected rather than certain or merely one remote possibility: If the service runs to schedule, the train the border just after midnight.
5
Choose the conversational form that treats the identity as a routine confident assumption: The phone's ringing at exactly eight. the maintenance engineer; he said he'd call then.
6
Choose the form that expresses a general possibility rather than uncertainty about one particular chart: Even technically accurate charts a trend if the scale is chosen badly.
7
Choose the form that introduces one specific possible explanation without presenting it as a conclusion: The discrepancy the result of an outdated data feed.
8
Choose the form that presents the consequence as quite possible but not certain: Removing the independent review public confidence in the process.
9
The speaker wants to sound maximally cautious. Choose the most deliberately tentative option: There a connection between the two anomalies, although the evidence is extremely limited.
10
Choose the strong negative deduction justified by the digital evidence: Omar in the archive room; his badge has not opened any door in that building today.

Degrees of certainty, deduction, possibility and expectation with modal verbs in present and future contexts

1
What would change if must be were replaced by should be?The server is responding to her credentials and her terminal is active; she must be logged in somewhere.
A.
B.
C.
2
Why would mustn't be normally be the wrong replacement?This can't be the approved version; the legal sign-off is absent.
A.
B.
C.
3
Which statement about may, might and could is most accurate?The discrepancy might be a synchronization issue.
A.
B.
C.
4
What is the best paraphrase of the highlighted modal?If the connection remains stable, the upload should finish within ten minutes.
A.
B.
C.
5
What is distinctive about That'll be here?There's someone at reception. That'll be the interpreter we booked for three o'clock.
A.
B.
C.
6
Why is can more natural than might for the intended generalisation?Small translation errors can alter the legal effect of a clause.
A.
B.
C.
7
Which interpretation of could be is correct?The sudden drop in pressure could be a sensor fault rather than a real leak.
A.
B.
C.
8
What nuance does may well add?The new approval layer may well delay routine cases more than expected.
A.
B.
C.
9
What is the best analysis of the speaker's stance?There might perhaps be a less disruptive way to restructure the service.
A.
B.
C.
10
What is the source of the modal meaning here?He can't be in the secure lab; the entry system shows no successful authentication since yesterday.
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B.
C.