Erasmus, Adagia 1.1.19
“The matter is on the hinge.”
“This saying is not wholly dissimilar to the last: the matter is on the hinge, which Servius suggested was a proveb as he related that of Vergil: ‘she will hardly withdraw from such a hinge of affairs’ and he thinks that it has this sense, as if one were to say, ‘The matter is at the deciding point.’ Cicero says instead, ‘the hinge turns on that,’ by which he means ‘the whole affair depends upon that.’ Quintilian, in his tenth book, writes, ‘I may remain silent concerning those (about whom I do not care) who neglect to consider where the hinge of the cases is turned.’
Quintilian also says in his fifth book, ‘If he confesses, he could argue that his garment could have been bloody for many other reasons; if he denies that his garment is bloody, he lays the hinge of the affair out on this claim, in which – if he be convicted of falsehood – he will be ruined in the rest of his subsequent claims.
The proverb is taken from doors, which are held up and turned about upon hinges.”
Res est in cardine (xix)
Huic non omnino diversum est illud : Res est in cardine, quod Servius proverbium esse admonuit enarrans illud Maronis : Haud tanto cessabit cardine rerum, putatque perinde valere, quasi dicas Res est in articulo. M. Tullius In eo cardo rei vertitur dixit pro eo, quod est : ex hoc tota res pendet. Quintilianus libro decimo : Nam ut taceam de negligentibus, quorum nihil refert, ubi litium cardo vertatur. Idem libro quinto : Nam si fatetur, multis ex causis potuit cruenta esse vestis ; si negat, hic causae cardinem ponit, in quo si victus fuerit, etiam in sequentibus ruit. Sumptum ab ostiis, quae cardinibus sustinentur volvunturque.