De Somniis (lib. i-ii)

But the impetuous course of these evils is most grievous when the irrational powers of the soul attack the powers of the reason and get the better of them;

for as long as the herds of oxen obey their drivers, and the flocks obey their shepherds, and the goats obey the goatherds, the herds and all belonging to them go on well; but when the herdsmen who are appointed to look after the cattle become weaker than the beasts committed to their care, then everything goes wrong, and instead of regularity there arises irregularity, and disorder in the place of order, and confusion instead of steadiness, and disturbance in the place of good arrangement, since there is no longer any lawful superintending power properly established; for if there had been such a thing, it would have been destroyed before this time.