In their subjective use, modal verbs shift away from expressing permission, obligation, or ability and instead convey the speaker's stance toward the truth of a claim. This use is common in journalism, academic writing, and narrative contexts where the speaker reports what someone said, believes, or likely did, without fully endorsing the claim. Each modal verb carries its own characteristic shade of meaning, and choosing among them allows the writer to fine-tune how confident, skeptical, or tentative the report should sound.
The verb wollen in subjective use expresses that someone claims something, while the speaker remains skeptical: Er will das gesehen haben means he claims to have seen it, with the implication that the speaker doubts it. Sollen conveys hearsay or unverified report: Sie soll sehr reich sein means she is said to be very rich. Müssen in subjective use signals a strong logical conclusion based on evidence: Er muss das gewusst haben means he must have known it, with near-certainty. These three modals form a rough gradient from outright skepticism through neutral reporting to confident inference.
Dürfen, in its Konjunktiv II form dürfte, expresses careful probability or polite assumption, softer than subjective müssen: Das dürfte stimmen means that is probably right. The subjective können signals theoretical possibility: Das kann stimmen means that may be true. The verb mögen expresses concessive possibility, acknowledging a point while implying that a counterpoint will follow: Das mag richtig sein, aber... This last usage is particularly useful in argumentation, because it allows the speaker to concede an opponent's point before countering it.
The past forms of subjective modals are constructed with the modal verb in the present tense plus a past infinitive, which combines the Partizip II of the main verb with haben or sein. So Er will Arzt gewesen sein means he claims to have been a doctor, and Sie soll krank gewesen sein means she is said to have been ill. Er muss es vergessen haben means he must have forgotten it. This construction preserves the modal's subjective nuance in past-tense narration and is essential for journalistic and academic reporting.