Subjuntivos: no creo que + subjuntivo

Question

No creo que + subjuntivo (cuando tenemos duda)

• Creo que hace calor aquí.
• No creo que haga calor aquí.

But I don't understand this sentence:

Creo que no hace calor aqui.

Answer 1

All that matters is whether the main clause is one of belief or non-belief. So a negative belief requires a subjunctive in the subordinate clause, no matter whether the subordinate clause is itself positively or negatively expressed.

• Creo que hace demasiado calor aquí. No me gusta.
• Creo que no hace demasiado calor aquí. Está bien.
• No creo que haga demasiado calor aquí. Está bien.
• No creo que no haga demasiado calor aquí, sino que sí lo hace.

(But avoid that last one if possible, as it is potentially confusing.)

So the mode of the subordinate clause has nothing to do with its own positivity or negativity. That said, there are scenarios that admit both, and you can tell by which one the speaker selects how certain they are of the matter:

• ¿Crees que viene?
• ¿Crees que venga?

In the second, the speaker is expressing their own lack of confidence in the questioned outcome.

The verb dudar works mostly opposite of creer in its choice of mode, taking now the subjunctive in the positive but (sometimes) the indicative in the negative:

• Dudo que haga calor aquí. Está bien.
• No dudo que hace calor aquí. Me va a matar si no tomo algo ahora mismo.

However, with dudar there is an increased tendency to use the subjunctive even when dudar is itself negated. To not do so, as I have just done above, means that the speaker is quite sure that there can be no doubt that this is certainly fact.

Answer 2

Last sentence is wrong and should be

Creo que no haga calor aquí

However you can hear mother tongues using it, although it's grammatically incorrect.