B1 · Lesson 11 · 20 min
Deductions about the present
In this lesson
- I can use must and can't to make strong deductions about now.
- I can use might, may and could for possible present situations without confusing them with rules.
Grammar in context
Noor is at a café. There are wet umbrellas by the door. “It must be raining outside,” she thinks. The owner’s coat is here, but Noor cannot see him. “He might be in the kitchen.” A package has someone else’s name on it. “This can’t be for me.”
Which words show a strong positive deduction, a possibility and a strong negative deduction? What clue supports each one?
Strong deductions: must and can't
Use must when the evidence makes you feel very sure something is true now. Use can't when the evidence makes you feel very sure something is not true. These words express your logical conclusion, not a rule or an obligation. After must and can't, use the base form of the verb. In questions, we usually ask about the evidence instead of using must for a deduction.
- The lights are off and the door is locked. The shop must be closed.
- Leo is answering the phone, so he can't be asleep.
Possible deductions: might, may and could
Use might, may or could when something is possible, but you are not certain. In many everyday situations, their meaning is very similar. Follow each modal with a base verb: might be, may live, could have. Use not after the modal for a possible negative: might not be. Do not use doesn't or isn't after a modal in this meaning.
- That woman might be the new neighbour, but I am not sure.
- The keys may not be in the kitchen; check your coat pocket.
Deductions are different from necessity
Must has two different jobs. For a deduction, it means 'I am sure': Sam must be at work because his car is not here. For necessity, it means 'it is necessary': Visitors must show a ticket. The situation and the evidence tell you which meaning is intended. Might, may and could do not express necessity; they show that one explanation is possible.
- This queue must be for the concert; everyone has wristbands.
- You must wear a helmet on this building site.
Common mistakes
Compare the incorrect and corrected forms.
Avoid
It must to be Maria at the door.
Use
It must be Maria at the door.
Use the base verb after must; do not add to.
Avoid
They might don't know the address.
Use
They might not know the address.
Put not directly after might, before the base verb.
Put it into practice
Try the exercises, write your own examples and check your understanding.