Aulus Gellius, Attic Nights (17.12):
“Even the ancients applied themselves to disgraceful subjects (or inconceivable, if you prefer), which the Greeks called adoxous hypotheseis. It was not only the sophists who did this, but real philosophers too. My main man Favorinus lowered himself to those subjects with the greatest cheer, thinking them fit either for clearing his mind, exercising his subtlety, or conquering difficulties with practice, just as when he sought some praise of Thersites, he praised a fever which recurred every four days and then spoke many things which were difficult to come up with on either side, and left them written in his books. He even brought Plato forth as a witness in the praises of the fever, saying that he wrote that one who suffers from quartan fever and recovers full strength will later enjoy more reliable and constant good health. Moreover, in those very same fever praises, he played around charmingly with this little idea: ‘The verse is well proven by the history of humanity: Sometimes the day is like a step-mother, sometimes like a mother.’ The line means that one cannot be doing well on every day, but do well on one day and poorly on another. Since this was the case, he said, ‘since in human life fortune is alternately good and bad, how much more fortunate is this fever broken by a two-day stretch: here we have one stepmother for every two mothers.'”
Infames materias, sive quis mavult dicere inopinabiles, quas Graeci adoxous hypotheseis appellant, et veteres adorti sunt non sophistae solum, sed philosophi quoque, et noster Favorinus oppido quam libens in eas materias se deiciebat vel ingenio expergificando ratus idoneas vel exercendis argutiis vel edomandis usu difficultatibus, sicuti, cum Thersitae laudes quaesivit et cum febrim quartis diebus recurrentem laudavit, lepida sane multa et non facilia inventu in utramque causam dixit eaque scripta in libris reliquit. Sed in febris laudibus testem etiam Platonem produxit, quem scripsisse ait, qui quartanam passus convaluerit viresque integras recuperaverit, fidelius constantiusque postea valiturum. Atque inibi in isdem laudibus non hercle hac sententiola invenuste lusit: “versus” inquit “est longo hominum aevo probatus::
ἄλλοτε μητρυιὴ πέλει ἡμέρη, ἄλλοτε μήτηρ.
Eo versu significatur non omni die bene esse posse, sed isto bene atque alio male. Quod cum ita sit,” inquit “ut in rebus humanis bene aut male vice alterna sit, haec biduo medio intervallata febris quanto est fortunatior, in qua est mia metryia, duo meteres?”