Modal Verbs of Deduction and Speculation

Modal verbs like can’t, might, may, could, and must are used to express different levels of certainty when making deductions or speculating about situations. Here’s how they work:

1. Must (High Certainty – 90-100%)

Used when we are almost sure that something is true.

• Present/Future: She must be at work now. (I’m almost certain.)
• Past: He must have forgotten his phone at home. (Strong deduction based on evidence.)

2. Can’t (High Certainty – 90-100%)

Used when we are almost sure that something is not true.

• Present/Future: He can’t be the thief; he was with me all day.
• Past: They can’t have finished the exam so quickly!

3. Might / May / Could (Low to Medium Certainty – 30-60%)

Used when something is possible but uncertain.

• Present/Future: She might be at home now. / He may arrive late. / They could be lost.
• Past: He might have missed the train. / She may have forgotten about the meeting. / They could have taken the wrong exit.

🔹 Differences between Might, May, and Could:

• Might/May are almost interchangeable, but "may" sounds slightly more formal.
• Could suggests a theoretical possibility rather than a strong likelihood.
  
  Now if you want to check how well you are at using the modal verbs of deduction and speculation, take the following test:
  https://forms.gle/jPSyC5msRGaN8rKK8