To Florus 3.119
And here you call someone a Caelestian for believing that anyone is free to do good. You therefore call free what you insist can do nothing but evil. Find, if you can, another definition of something unfree, and claim this as free! Even if you had lost your senses so completely that you could not see freedom’s definition in the thing itself, ought you not to have understood freedom’s essence from its opposite?
Suppose you were similarly uncertain what eyesight meant and defined it as follows: Sight means having the eyes gouged out, or being unable to see anything through some obstruction when it is time to see. Suppose you thought this definition fitted sight, but then turned to explain its opposite, blindness. You could find no other explanation except that, in an animal whose nature includes eyesight, the eyes have been gouged out or blocked by thick fluid, taking away the ability to see. You would surely come to your senses and recognize that one definition cannot fit contrary things.
Then, if blindness could mean only the deprivation of sight in an animal’s eye when it should be able to see, the definition of sight would emerge by denying the conditions used to explain blindness. Sight would be the proper capacity to see at the appropriate time, with eyes neither gouged out nor blocked. If you stubbornly resisted after this was shown, you would achieve only this: listeners would either think you opposed your own conscience with shameful obstinacy, or, if you convinced them that you really thought this way, they would judge your mind’s eyes as thoroughly gouged out as those of the person you had defined as possessing sight.
Latin
Et hic Caelestianum dicis, qui putat liberum esse quemquam ad agendum bonum; liberum ergo dicis, quod nisi malum facere non posse contendis. Inveni, si potes, alteram definitionem rei non liberae et hoc liberum vindicato, si adeo sensu excideras, ut definitionem liberi in suo corpore non videres, vel de contrario eius non debuisti intellegere, quae esset libertatis essentia. Fac enim te similiter ambigere potuisse, quid esset, quod visus diceretur oculorum, idque tu definires hoc modo: visus est vel effossos habere oculos vel impedimentis quibusque videndi tempore nihil posse conspicere, atque hanc definitionem putares visui convenire, referres te autem, ut contrarii eius id est caecitatis quae explicatio esset assereres, cumque nullam aliam invenires, quam si in eo animali, cuius naturae adesset visus oculorum, vel effossio luminum vel crassi humoris obsaeptio videndi eripiens facultatem, resipisceres procul dubio et videres rebus contrariis definitionem unam non posse competere. Sicque fiebat, ut, si caecitas nihil dici aliud poterat quam in animalis oculo eo tempore, quo videre deberet, privatio cernendi, visus quoque definitio per negationem illorum, quibus caecitatem exposueras, redderetur, ut videlicet nihil esset aliud visus quam nec effossis nec obseratis oculis opportuno tempore facultas congrua conspicandi. Quibus tu ostensis, si obstipe reluctareris, nihil obtineres aliud, quam ut aut contra conscientiam tuam pervicacia pudenda niti te crederent audientes aut, si eis fidem faceres tibi ita prorsus videri, non te minus effossos habere mentis oculos iudicarent quam illum, qui a te visum habens fuerat definitus.