Doubt and Denial (Duvidar que, Não acreditar que)

One of the cleanest, most learnable uses of the conjuntivo (what Brazilians call the subjuntivo) is to mark doubt, disbelief, and denial. When the main clause signals that the speaker is uncertain about what follows — or is actively rejecting it — the verb in the subordinate clause jumps from the indicative into the subjunctive. The underlying logic is simple: the indicative anchors statements in reality, while the subjunctive handles everything the speaker is not prepared to vouch for.

The core pattern

Main clause (doubt / denial) + que + present subjunctive

If the main verb or expression casts uncertainty on what follows, the verb after que goes into the present subjunctive.

Common triggers of doubt and denial

These expressions reliably take the subjunctive:

• duvidar que — to doubt that
• não acreditar que — to not believe that
• não crer que — to not believe that (slightly more formal)
• não achar que — to not think that
• não pensar que — to not think that
• negar que — to deny that
• não ser verdade que — it's not true that
• não ser certo que — it's not certain that
• não ser evidente que — it's not evident that
• não ser óbvio que — it's not obvious that
• não parecer que — it doesn't seem that
• não estar certo/seguro de que — to not be sure that

Notice the pattern: most of these expressions are negative versions of belief or certainty verbs. The negation is what injects the doubt. Affirmative versions of the same verbs (acredito que, acho que, é verdade que) take the indicative — we'll return to that contrast shortly.

Acreditar que vs. não acreditar que — the classic contrast

This is the pair every learner needs to internalize. In the affirmative, acreditar que expresses a belief the speaker holds to be true, so it takes the indicative. Once you negate it, não acreditar que expresses disbelief — the speaker is actively withholding commitment — so it flips to the subjunctive.

The first sentence projects confidence; the second projects doubt. The mood of the verb follows that projection mechanically. The same logic applies to achar que, pensar que, estar certo de que, and ser verdade que: affirmative takes the indicative, negative takes the subjunctive.

Questions: it depends on what you expect

In questions, the choice of mood reflects the speaker's own expectation. If you genuinely have no idea what the answer is — or if you suspect the answer might be "no" — the subjunctive is natural. If you expect confirmation, use the indicative.

Both are grammatical. The subjunctive version is more tentative — it leans toward "you don't really think he'll come, do you?" In everyday European Portuguese, the indicative version is more frequent in neutral questions; the subjunctive creeps in when the speaker is actively hedging.

Negar que and não negar que

Negar que (to deny that) takes the subjunctive because denial is, by definition, the rejection of a claim. Interestingly, its own negation — não negar que (to not deny that) — typically takes the indicative, because a double negative returns you to an affirmation.

The same logic applies to não duvidar que: when you "don't doubt" something, you're in fact asserting it, and the indicative reappears.

Talvez, possivelmente, provavelmente — adverbs of doubt

A small but important family of adverbs meaning "perhaps" or "probably" also triggers the subjunctive when they introduce the clause. The most important — and the only one that triggers it categorically — is talvez, which in European Portuguese almost always pulls the subjunctive along with it.

Adverbs like possivelmente and provavelmente are variable — most EP speakers use them with the indicative in everyday speech, but the subjunctive is also attested, particularly when the speaker wants to emphasise uncertainty. Both are acceptable.

Se calhar — the PT-PT alternative that keeps the indicative

This is a European Portuguese detail worth flagging. Se calhar means "maybe" / "perhaps" and is enormously common in everyday Lisbon speech — but unlike talvez, it takes the indicative, not the subjunctive. Brazilian Portuguese does not use se calhar at all, which is one of the quickest ways to tell spoken EP apart from BP.

Compare directly:

• Talvez vá ao Porto. — subjunctive, slightly more formal
• Se calhar vou ao Porto. — indicative, everyday PT-PT

Both mean the same thing. The mood choice is dictated by the adverb, not the speaker's degree of certainty.

Impersonal expressions of doubt

A handful of impersonal constructions follow the same affirmative-vs-negative logic we saw with acreditar, with one wrinkle: some of them are already uncertain in the affirmative, so they take the subjunctive in both polarities.

• é possível que
  • subjunctive (possibility = uncertainty, even affirmative)
• é provável que
  • subjunctive
• pode ser que
  • subjunctive
• não é certo que
  • subjunctive
• não é seguro que
  • subjunctive

These are covered in more depth on the impersonal expressions page.

Common mistakes

These are the errors English speakers make most consistently when learning EP doubt triggers.

The pattern in all five mistakes is the same: English has no morphological subjunctive, so English speakers reach reflexively for the indicative after verbs of doubt. Training yourself to hear the negation as a mood trigger is the single most productive habit you can build at this stage.

Key takeaways

• Affirmative belief = indicative. Negated belief = subjunctive.
• Talvez triggers the subjunctive; se calhar (PT-PT specific) does not.
• Negar que takes the subjunctive; não negar que returns to the indicative.
• In questions, the subjunctive signals that the speaker is already skeptical of the answer.
• The subjunctive is alive and well in everyday European Portuguese — Lisbon speakers use it constantly in casual speech.

For side-by-side minimal pairs across all the major triggers, see Subjunctive vs Indicative: Key Contrasts. For impersonal constructions like é possível que, see Impersonal Expressions.