Modal verbs: deduction and past modals

Modal Verbs: Advanced Uses

Modal verbs (can, could, may, might, will, would, shall, should, must, ought to, need) express ability, possibility, permission, obligation, deduction, and advice. At B1+ level, we focus on their more nuanced and advanced uses.

Modals of deduction (present)

• Must + base form (logical certainty, affirmative): "She has been studying all day. She must be exhausted." (I am almost sure.)
• Cannot / could not + base form (logical certainty, negative): "He cannot be at home - I just saw him at the shop."
• May / might / could + base form (possibility): "She might be at the library." "It could rain later." (It is possible but not certain.)

Modals of deduction (past)

• Must have + past participle (logical certainty about the past): "He must have forgotten about the meeting." (I am almost sure he forgot.)
• Cannot / could not have + past participle (impossibility in the past): "She cannot have said that - she is always so polite."
• May / might / could have + past participle (past possibility): "He might have taken the wrong train." "She could have left her phone at home."

Should have / ought to have + past participle

Criticism or regret about the past (something was advisable but was not done):

• "You should have told me earlier." (But you did not tell me.)
• "She ought to have studied more." (But she did not.)
• "I should not have eaten so much." (But I did.)

Could have + past participle

Unrealised past ability or missed opportunity:

"I could have helped you, but you did not ask." (I had the ability, but the action did not happen.)

"We could have won the match if we had played better."