Why does a conjuction like “à moins que” take the subjunctive even though it expresses conditions?

Question

Why isn't the indicative used after “à moins que”, if the action we are talking about has a great percentage of happening, or the imparfait, if the action is a bit far-fetched, and if they can be used what will be the difference in meaning?

I also wonder why a conjunction like although is used with the subjunctive. In a sentence like this, for example, I have no idea why there can be any uncertainty or emotions involved in order to use the subjunctive

Quoiqu'il fasse froid, ils se promènent dans la forêt.

Answer 1

À moins que is introducing an hypothetical fact, so the subjunctive is used.

Quoique is introducing a real fact, but this fact is breaking the logic of the main statement.

This is called a concessive statement. Depending on what conjunction is used, concessive statement require either the subjunctive or the indicative/conditional in French.

Subjunctive (the conjunction clearly introduces a concession):

• Bien qu'il fasse/ait fait/fît/eût fait froid,...

• Encore qu'il fasse/... froid,...

• Quoiqu'il fasse/... froid,...

• Malgré le fait qu'il fasse/... froid,...

• Sans qu'il fasse froid,...

Indicative/Conditional (the conjunction introduces a softer concession, or no concession at all for the last case, all are more observations) :

• Alors qu'il faisait/fait/fera/ferait/aurait fait/... froid,...

• Alors même qu'il faisait/fait/... froid,...

• Tandis qu'il faisait/fait/... froid,...

• Pendant qu'il faisait/fait/... froid,...

Where there is no concession but a logical cause, the indicative or conditional is expected too:

• Puisqu'il faisait/fait/fera/ferait/... froid,...
• Parce qu'il faisait/fait/fera/ferait/... froid,...

There is also the controversial malgré que which should require the subjunctive but which is more often followed by the indicative in relaxed colloquial spoken French:

• Malgré qu'il fait froid,...