Subjunctive vs Indicative: Doubt and Denial

You have met the subjunctive after wishes and after emotion. The third great trigger is doubt, and it comes with the sharpest subjunctive-versus-indicative contrast in the whole system. Where the earlier triggers were one-way streets, doubt sets up a genuine fork: the same verb takes the indicative when you are confident and the subjunctive when you are not.

This page assumes you can already build the forms. If venga, sea, sepa and haya look unfamiliar, start with how to form the present subjunctive and come back.

The logic: do you vouch for it?

The subjunctive marks a clause you are holding at arm's length. When you assert that something is true, you put your weight behind it, and Spanish keeps the indicative. When you doubt, deny or disbelieve it, you withdraw that weight, and the clause flips to the subjunctive.

• Creo que viene. (I think he's coming.) - you are asserting it, indicative.
• No creo que venga. (I don't think he's coming.) - you are doubting it, subjunctive.

Same verb, same event, two moods, decided entirely by whether you are vouching for the fact or backing away from it.

The trigger verbs of doubt and denial

These verbs and phrases withdraw confidence from the following clause, so they push it into the subjunctive.

• dudar que - to doubt that: Dudo que sea verdad. (I doubt it's true.)
• no creer que - not to think that: No creo que venga. (I don't think he's coming.)
• no pensar que - not to think that: No pienso que tenga razón. (I don't think he's right.)
• no estar seguro de que - not to be sure that: No estoy seguro de que lo sepa. (I'm not sure he knows.)
• negar que - to deny that: Niega que la conozca. (He denies knowing her.)
• no es verdad que - it's not true that: No es verdad que venga. (It's not true that he's coming.)
• es imposible que - it's impossible that: Es imposible que lo termine hoy. (It's impossible he'll finish it today.)
• es improbable que - it's unlikely that: Es improbable que llueva. (It's unlikely it'll rain.)

The common thread is uncertainty or rejection. You are either weighing the clause and finding it doubtful, or denying it outright. Either way you are not asserting it as fact, and the subjunctive marks that.

The indicative counterparts: confident assertion

The mirror image of the doubt list is the assertion list. When you say you think, believe or know something, or when you flag it as true, certain or obvious, you are vouching for the clause, so it stays in the indicative.

• creer que - to think that: Creo que viene. (I think he's coming.)
• pensar que - to think that: Pienso que tiene razón. (I think he's right.)
• estar seguro de que - to be sure that: Estoy seguro de que lo sabe. (I'm sure he knows.)
• es verdad que - it's true that: Es verdad que trabaja mucho. (It's true he works a lot.)
• es evidente que - it's obvious that: Es evidente que sabe. (It's obvious he knows.)

These are confident statements. They report the clause as fact, so the indicative is correct. The certainty impersonals (es verdad que, es evidente que) are covered in more depth on the impersonal expressions page; here they matter because they obey exactly the same flip as creer and pensar.

The negation flip

This is the heart of the page. Confident verbs take the indicative when affirmative and the subjunctive when negated, because the no is what destroys the confidence.

The flip runs the other way too. Negar denies, so it is already in doubt territory and takes the subjunctive; negate it back to no negar and you are now asserting the thing is true, so it returns to the indicative.

• Niega que la conozca. (He denies knowing her.) - denial, subjunctive.
• No niega que la conoce. (He doesn't deny he knows her.) - effectively an assertion, indicative.

The rule under all of this: ask whether the speaker is vouching for the clause. A double negative that lands back on an assertion takes the indicative.

Quizás, tal vez and posiblemente

The "maybe" adverbs - quizás (also spelled quizá), tal vez and posiblemente - are a special case, because the mood tracks how real the doubt is.

• Quizás venga. (Maybe he'll come.) - genuine uncertainty, subjunctive.
• Quizás viene. (Maybe he's coming.) - the speaker leans towards yes, indicative.

When the doubt is real and open, use the subjunctive. When you are fairly sure and "maybe" is just politeness or hedging, the indicative is allowed. Both are correct Spanish; they encode different degrees of confidence. The same choice applies to tal vez and posiblemente.

One adverb breaks ranks: a lo mejor, another everyday word for "maybe", always takes the indicative despite meaning the same thing. A lo mejor viene is the only option. It is an idiom, so do not try to apply the doubt logic to it.

Worked examples

• Creo que es verdad. (I think it's true.) - assertion, indicative.
• No creo que sea verdad. (I don't think it's true.) - doubt, subjunctive.
• Dudo que lleguen a tiempo. (I doubt they'll arrive on time.) - doubt, subjunctive.
• Estoy seguro de que ganamos. (I'm sure we'll win.) - confidence, indicative.
• No estoy seguro de que ganemos. (I'm not sure we'll win.) - doubt, subjunctive.
• Es imposible que lo sepa. (It's impossible he knows.) - denial of possibility, subjunctive.
• Niega que robara el dinero. (He denies stealing the money.) - denial, subjunctive.
• Quizás tengas razón. (Maybe you're right.) - open doubt, subjunctive.
• A lo mejor tienes razón. (Maybe you're right.) - a lo mejor, indicative.

Subjunctive vs indicative practice

This is the one corner of the subjunctive where practice matters more than anywhere else, because the choice is a live fork rather than a fixed trigger: the same verb goes both ways and only the speaker's confidence decides. The test yourself quiz below drills the fork directly - an indicative-or-subjunctive round on the bare triggers, gap-fills where creo que and no creo que sit side by side, and translations that make you flip the mood with the negation. If you can clear the negation-flip questions cold, you have the hardest decision in the mood system under control. The printable worksheets carry the same exercises with answer keys.

Common mistakes English speakers make

Keeping the indicative after the negated verb. The instinct is to say no creo que viene, reusing the indicative from the affirmative creo que viene. But negating creer turns assertion into doubt, so it has to be no creo que venga. The negation is the switch; flip the verb with it.

Forcing the subjunctive after affirmative creer and pensar. The opposite error, made by learners who have overlearned "doubt takes the subjunctive". Creo que is confident, so creo que venga is wrong; it must be creo que viene. Only the negated versions take the subjunctive.

Treating quizás as a fixed subjunctive trigger. Both quizás venga and quizás viene are correct, and a lo mejor never takes the subjunctive at all. Do not mechanically swap every "maybe" to the subjunctive; the mood reflects how genuine the doubt is, and a lo mejor sits stubbornly outside the rule.

Get the negation flip, the affirmative-stays-indicative half, and the quizás wobble straight, and doubt joins wishes and emotion as a third fluent slice of the subjunctive. The machinery is the same; only the trigger - and the fork - has changed.

See also

• The subjunctive after impersonal expressions - es posible que and es verdad que, where the certainty-versus-doubt split and the negation flip are mapped for impersonals.
• The subjunctive after emotion - me alegro de que and the rest of the emotional reactions.
• How to form the present subjunctive - the endings, the yo-stem rule and the six irregulars you need for any of these sentences.
• The Spanish grammar cheatsheet has the doubt-versus-assertion list and the negation flip on one card.