Plutarch, De communibus notitiis adversus Stoicos
Goodwin, Ed.

And if Nature had absolutely stood in need of the generation of evil, yet might one or two examples of vice have been sufficient; or if you will, it might have been requisite that ten, a thousand, or ten thousand vicious men should be brought forth, and not that the multitude of vices should be so great as ‘to exceed in number the sands of the sea, the dust of the earth, and the feathers of all the various kinds of birds in the world,’ and yet that there should not be so much all this while as a dream of virtue. Those who in Sparta had the charge of the public halls or eating places called Phiditia, were wont to bring forth two or three Helots drunken and full of wine, that the young men, seeing what drunkenness was, might learn to keep sobriety. But in human life there are many [p. 390] such examples of vice. For there is not any one sober to virtue; but we all stagger up and down, acting shamefully and living miserably. Thus does reason inebriate us, and with so much trouble and madness does it fill us, that we fall in nothing short of those dogs of whom Aesop says, that seeing certain skins swimming on the water, they endeavored to drink the sea up, but burst before they could get at them. For reason also, by which we hope to gain reputation and attain to virtue, does, ere we can reach to it, corrupt and destroy us, being before filled with abundance of heady and bitter vice;—if indeed, as these men say, they who are got even to the uppermost step have no ease, cessation, or breathing from folly and infelicity.