Subjunctive after doubt and denial

No crec que vingui presents the coming as something the speaker does not affirm. No em sembla que sigui fàcil has the same useful learner pattern. The embedded verb's person depends on its own subject.

Dubto que sigui veritat explicitly introduces doubt. No és segur que arribi avui withholds certainty. In these neutral constructions, the subjunctive presents the embedded situation without asserting it as fact.

The subjunctive does not mean that the event is impossible or false; it reflects how the clause is presented under doubt, denial or another nonassertive frame. An affirmative sé que or és clar que normally uses indicative when asserting certainty. Discourse can change the intended scope of a negation, so learn the ordinary contrasts without turning them into a purely mechanical no-equals-subjunctive rule for every sentence.