Modal verbs used subjectively (er dürfte krank sein)

Beside their normal ("objective") meaning of ability, permission or obligation, modal verbs have a subjective use: they express how certain the speaker is about a statement. The modal is conjugated and combines with an infinitive.

A rough scale of certainty:

• muss - almost certain ("must be")
• müsste / dürfte - probably, quite likely
• könnte - possibly, maybe
• kann - it is possible
• mag - admittedly may (concessive)

Examples:

• Er dürfte jetzt zu Hause sein. - He is probably home by now.
• Sie muss krank sein, sie ist nicht gekommen. - She must be ill, she didn't come.
• Das könnte stimmen. - That could be true.

Common mistakes. Don't read these as the literal meaning: Er dürfte krank sein means "he is probably ill", not "he is allowed to be ill". The context (a guess about a fact) tells you it is the subjective use. For a guess about the past, combine the modal with a perfect infinitive: Er dürfte krank gewesen sein ("he was probably ill"). Compare this with Futur I + wohl (Er wird wohl krank sein), which expresses a very similar assumption.

Modal verbs can express the speaker's assumption about how certain something is.

Used subjectively, modal verbs grade certainty: 'muss' (almost certain), 'müsste/dürfte' (probably), 'könnte' (possibly). They stand with an infinitive like normal modals.

Modalverben können auch eine Vermutung über den Grad der Sicherheit ausdrücken.