Douter vs. se douter (douter que / se douter que)

Douter and its reflexive counterpart se douter are near opposites. Because of this, they trigger different moods.

Douter que + Subjunctive

Douter que means "to doubt that." Because it expresses uncertainty, it takes the subjunctive.

I doubt that this painting is a masterpiece.
Je doute que ce tableau soit un chef-d'œuvre.
The expert doubts that the forger has the best technique.
L'expert doute que le faussaire ait la meilleure technique.

Se douter que + Indicative

Se douter que means "to suspect that" or "to have a strong feeling that." Since it expresses a strong belief that something is a fact, it takes the standard indicative mood.

We suspect that the forger comes from Paris.
On se doute que le faussaire vient de Paris.
The museum suspects that the provenance is false.
Le musée se doute que la provenance est fausse.

Comparing the Two

Notice the mood difference when investigating a potential forgery:

They doubt that the provenance is authentic, so they ask for an appraisal.
Ils doutent que la provenance soit authentique, alors ils demandent une expertise.
She suspected that the appraisal was completely false.
Elle se doutait que l'expertise était tout à fait fausse.