Use must plus the base verb for a strong conclusion that something is true, as in she must be tired, can’t for a strong conclusion that something is not true, as in he can’t be at home, and might, may, or could for an uncertain possibility. These modals express logical conclusions about the present based on evidence.
Grammar Rule
These modals make logical conclusions about the present based on evidence, with different degrees of certainty.
Modals of Deduction (Present): Rules and Examples
| Modal | Certainty | Example |
|---|---|---|
| must | strong certainty it’s true | She must be tired after the trip. |
| can’t | strong certainty it’s not true | He can’t be at home; the lights are off. |
| might / may / could | uncertain possibility | They might be at the office right now. It could be true, but I’m not sure. |
Remember: must for near certainty, can’t for near-impossible, might/may/could for possibility.
Practice Test
Instructions
Answer each question in the test below using the correct modal of deduction for the present. You will get a new random set of questions every time you retake the test, plus a downloadable results summary with your name and score at the end.
Modals of Deduction – Present
Click «Start the test» to begin right away — no signup required. You can get a personalized certificate with your name and score at the end, if you want one.
Frequently Asked Questions
How do you express near certainty about the present?
Use must plus the base verb, as in she must be tired after the trip.
How do you express that something is almost certainly not true?
Use can’t plus the base verb, as in he can’t be at home, the lights are off.
Which modals express uncertain possibility?
Might, may, and could, as in they might be at the office right now.
Are these modals based on evidence or pure guessing?
They are based on evidence or logical reasoning, not random guessing, which is why they are called modals of deduction.