Breakdown of Dans cette fable, il fallait que le renard fût très rusé.
être
to be
très
very
dans
in, inside
ce
this (before a noun)
Questions & Answers about Dans cette fable, il fallait que le renard fût très rusé.
Why do we see fût here instead of the regular present subjunctive soit?
Because this sentence uses the imperfect subjunctive, which you will often see in literature. In formal written French, when the main verb (il fallait) is in a past tense, the subjunctive verb in the dependent clause shifts to a past form to match it. In everyday spoken French, you would just hear il fallait que le renard soit.
How can I tell that fût is the imperfect subjunctive and not the passé simple?
The circumflex accent on the û is the exact clue you need. The passé simple of être is il fut (no accent). The imperfect subjunctive adds the circumflex to make it qu'il fût. This accent appears on almost all third-person singular verbs in the imperfect subjunctive.
What triggers the subjunctive mood here in the first place?
The impersonal expression il fallait que (it was necessary that). In French, expressions of necessity, obligation, doubt, or strong emotion almost always require the following verb to be in the subjunctive mood.
Could fût be a form of the verb faire instead of être?