Advanced Modal Meanings: Speculation & Deduction
What Are Modal Verbs?
Modal verbs (must, might, could, may, can’t, couldn’t, should) help us express how certain or uncertain we are about something. When used for speculation and deduction, they indicate how confident we are in our conclusions about present or past situations.
Speculation: Talking About Possibilities
Speculation means making guesses about something when we don’t have complete information. We use different modals depending on how likely we think something is.
Certainty Scale for Present Speculation
can’t / couldn’t be
might / may / could
should / ought to
must
Present Speculation
For present situations, we use: modal + base verb
“She must be at work.” (I’m very confident she’s at work)
“He might be sleeping.” (It’s possible he’s sleeping)
“They can’t be serious!” (I’m sure they’re not serious)
“It could be raining there.” (Maybe it’s raining, maybe not)
Past Speculation
For past situations, we use: modal + have + past participle
“She must have forgotten the meeting.” (I’m very sure she forgot)
“He might have left early.” (Perhaps he left early)
“They can’t have finished already!” (I’m sure they haven’t finished)
“You could have been right.” (Maybe you were right)
Deduction: Drawing Logical Conclusions
Deduction is when we use evidence or logic to reach a conclusion. We look at the facts we have and make an informed judgment about what must be true, what’s probably true, or what’s impossible.
Evidence: The lights are off and the door is locked.
Deduction: “They must have gone home.” (logical conclusion based on evidence)
Evidence: Her eyes are red and she looks upset.
Deduction: “She must have been crying.” (past deduction)
Evidence: He’s wearing shorts and a t-shirt in winter.
Deduction: “He can’t be cold.” (negative deduction – seems impossible)
Key Differences
Must: Used for strong deductions (almost certain based on evidence)
Might/May/Could: Used for possibilities (we’re not sure)
Can’t/Couldn’t: Used for negative deductions (we’re sure it’s not true)
Should: Used for expectations (we think it’s likely)
“She must be a doctor.” (I’m almost certain – strong evidence)
“She might be a doctor.” (It’s possible, but I’m not sure)
“She should be a doctor by now.” (I expect this because she was studying medicine)
“She can’t be a doctor.” (I’m certain she’s not – she never went to medical school)
📝 Check Your Understanding
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