Boethius, Consolation of Philosophy
4 pr. 3 (tr. W.V. Cooper):
Then, from the other point of view of the good, see what a punishment ever goes with the wicked. You have learnt a little while past that all that exists is one, and that the good itself is one; it follows therefrom that all that exists must appear to be good. In this way, therefore, all that falls away from the good, ceases also to exist, wherefore evil men cease to be what they were. The form of their human bodies still proves that they have been men; wherefore they must have lost their human nature when they turned to evil-doing. But as goodness alone can lead men forward beyond their humanity, so evil of necessity will thrust down below the honourable estate of humanity those whom it casts down from their first position. The result is that you cannot hold him to be a man who has been, so to say, transformed by his vices.
If a violent man and a robber burns with greed of other men's possessions, you say he is like a wolf. Another fierce man is always working his restless tongue at lawsuits, and you will compare him to a hound. Does another delight to spring upon men from ambushes with hidden guile? He is as a fox. Does one man roar and not restrain his rage? He would be reckoned as having the heart of a lion. Does another flee and tremble in terror where there is no cause of fear? He would be held to be as deer. If another is dull and lazy, does he not live the life of an ass? One whose aims are inconstant and ever changed at his whims, is in no wise different from the birds. If another is in a slough of foul and filthy lusts, he is kept down by the lusts of an unclean swine. Thus then a man who loses his goodness, ceases to be a man, and since he cannot change his condition for that of a god, he turns into a beast.
Vide autem ex adversa parte bonorum quae improbos poena comitetur; omne namque quod sit unum esse ipsumque unum bonum esse paulo ante didicisti; cui consequens est ut omne quod sit id etiam bonum esse uideatur. Hoc igitur modo quicquid a bono deficit esse desistit. Quo fit ut mali desinant esse quod fuerant. -- Sed fuisse homines adhuc ipsa humani corporis reliqua species ostentat -- Quare versi in malitiam humanam quoque amisere naturam. Sed cum ultra homines quemque provehere sola probitas possit, necesse est ut quos ab humana condicione deiecit infra homines meritum detrudat improbitas; evenit igitur ut quem transformatum vitiis videas hominem aestimare non possis.
Avaritia fervet alienarum opum violentus ereptor: Lupis similem dixeris. Ferox atque inquies linguam litigiis exercet: Cani comparabis. Insidiator occultus subripuisse fraudibus gaudet: Vulpeculis exaequetur. Irae intemperans fremit: Leonis animum gestare credatur. Pavidus ac fugax non metuenda formidat: Cervis similis habeatur. Segnis ac stupidus torpet: Asinum vivit. Levis atque inconstans studia permutat: Nihil avibus differt. Foedis immundisque libidinibus immergitur: Sordidae suis voluptate detinetur. Ita fit ut qui probitate deserta homo esse desierit, cum in divinam condicionem transire non possit, vertatur in beluam.