Modals of Deduction (Present)

• When we want to make logical guesses about something in the present based on clues, we use modal verbs of deduction. The modal we choose depends on how sure we are.
• Modal
• Meaning / Level of Certainty
• Example
• must
• Almost 100% sure (logical conclusion)
• He hasn't called back; he must be busy in Boston.
• might / could
• About 50% sure (possibility)
• She might know about the budget freeze in Chicago.
• can't
• Almost 100% sure that something is impossible
• That can't be a serious buyer from New York.
• Remember
• Use 'must' when the evidence strongly supports your conclusion.
• Use 'might' or 'could' when something is possible, but you are not certain.
• Use 'can't' when the evidence shows something is impossible.
• Never use 'mustn't' for deductions; 'mustn't' means prohibition.
• Examples
• Mark is reading the room well; he must understand the client.
• That cold email might generate some real interest in Seattle.
• They can't be tyre-kickers because they have a huge budget.
• Common mistakes
• He mustn't be interested in our offer in Austin.
• He can't be interested in our offer in Austin.

Complete the sentences

• The client in Seattle hasn't replied for a week; he (must) ____ be very busy with the account review.
• That buyer from Denver asked about prices, so she (might) ____ be a serious buyer.
• They told us they have no money at all, so this (can't) ____ be a real interest.
• Listen to his voice; he (could) ____ be hiding something from us.
• She sent an automatic out-of-office reply; she (must) ____ be traveling to London today.
• They are just looking at window displays in Manchester; they (can't) ____ want to purchase anything today.

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