So too with our minds. If we do not keep them busy with some particular subject which can serve as a bridle to rein them in, they charge ungovernably about, ranging to and fro over the wastelands of our thoughts. Then, there is no madness, no raving lunacy, which such agitations do not bring forth.

[Ainsi est-il des esprits, si on ne les occupe à certain sujet, qui les bride & contraigne, ils se jettent desreglez, par-ci par là, dans le vague champ des imaginations. Et n’est follie ny réverie, qu’ils ne produisent en cette agitation.]

Michel de Montaigne (1533-1592) French essayist

Essays, Book 1, ch. 8 “Of Idleness [De l’Oisiveté]” (1572) (1.8) (1595) [tr. Screech (1987)]
    (Source)

This essay was in the 1st ed. (1595); though the essay was revised for later editions, this text was not. The Essays themselves were begun to cure the melancholy and unrestrained thoughts caused by Montaigne's moving to his country estates, retiring from public life, and isolating himself in the château library for some time. This essay speaks to that experience.

(Source (French)). Alternate translations:

So is it of minds, which except they be busied about some subject, that may bridle and keepe them under, they will here and there wildely scatter themselves through the vaste field of imaginations. And there is no follie, or extravagant raving, they produce not in that agitation.
[tr. Florio (1603)]

So it is with Wits, which if not applyed to some certain Study that may fix and restrain them, run into a thousand Extravagancies, and are eternally roving here and there in the inextricable Labyrinth of restless Imagination. In which wild and irregular Agitation, there is no Folly, nor idle Fancy they do not light upon.
[tr. Cotton (1686)]

So it is with our minds, which, if not applied to some particular subject to check and restrain them, rove about confusedly in the vague expanse of imagination. In which agitation there is no folly nor idle fancy which they do not create.
[tr. Friswell (1868)]

So it is with minds, which if not applied to some certain study that may fix and restrain them, run into a thousand extravagances, eternally roving here and there in the vague expanse of the imagination -- in which wild agitation there is no folly, nor idle fancy they do not light upon.
[tr. Cotton/Hazlitt (1877)]

So it is with our minds. If we do not apply them to some sort of study that will fix and restrain them, they will drift into a thousand extravagances, and will sternly run here and there in an inextricable labyrinth of restless imagination. In this wild and irregular agitation there is no folly nor idle fancy they do not touch upon.
[tr. Rector (1899)]

So it is with our minds: if we do not keep them occupied with a distinct subject, which curbs and restrains them, they run aimlessly to and fro, in the undefined field of imagination. And there is no folly or fantasy to which they do not give birth in this agitation.
[tr. Ives (1925)]

So it is with minds. Unless you keep them busy with some definite subject that will bridle and control them, they throw themselves in disorder hither and yon in the vague field of imagination. And there is no mad or idle fancy that they do not bring forth in this agitation.
[tr. Frame (1943)]

So it is with our minds. If we do not occupy them with some definite subject which curbs and restrains them, they rush wildly to and fro in the ill-defined field of the imagination. And there is no folly or fantasy that they will not produce in this restless state.
[tr. Cohen (1958)]

If [minds] have no object to busy themselves with, something to check and restrain them, they will run free and ramble through the open field of their imagination. And in this state of excitement, minds will come up with all kinds of foolishness and fantasies.
[tr. HyperEssays (2025)]