Cap. VIII Arg. 6 Ad ultimum: merit of hardening in original sin; further hardening from daily sins; decree from free will
To the last testimony — Augustine teaching that we easily find in ourselves the merit of hardening, but cannot find the merit of divine mercy — I answer: he is not speaking of foresight of actual sins lasting to life's end in this or that person, but of original sin, the common demerit of all Adam's children. That can stand as sufficient cause why divine mercy may be denied anyone without any show of cruelty; it cannot stand as cause why God refused to prepare and apply to this or that particular man an efficacious remedy by which that inborn hardness could be tamed. Original sin avails for inquiring into damnation; it does not avail as the cause of negative reprobation. Finally all the reprobate — especially those who reach the use of free will — are said to merit that hardening: negatively, because they do not merit softening or that special mercy; affirmatively, because by daily sins they merit further hardening and handing over to a reprobate mind (Rom. 1:28). Yet the reprobation decree by which they are permitted so to harden depends on God's freest will, not on their foresighted final hardness — which could not be foresighted unless that permitting decree were presupposed.
Latin
Ad ultimum testimonium, in quo Augustinus docet facile posse nos invenire in nobis meritum obdurationis, sed meritum misericordiae Divinae non posse invenire, respondeo, loqui illum non de praevisione actualium peccatorum ad finem vitae in hoc vel illo perdurantium, sed de originali peccato, quod est quasi commune demeritum in omnibus Adae filiis, et potest allegari tanquam sufficiens causa, cur Divina misericordia cuivis possit absque omni crudelitatis specie denegari, sed non potest allegari tanquam causa, cur Deus noluerit huic vel illi singulari homini efficax remedium praeparare et adhibere, quo haec ingenita durities edomari posset. Valet igitur originalis peccati consideratio, ut inde inquiras damnationis, sed non eo valet ut inde petatur causa negativae reprobationis. Denique dicuntur omnes reprobi, praesertim qui ad usum liberi arbitrii perveniunt, mereri istam obdurationem, primo, sensu negativo, quia non merentur emollitionem, quia non merentur specialem illam misericordiam; deinde, sensu affirmativo, quia quotidianis suis peccatis merentur illam ulteriorem obdurationem et traditionem εἰς ἀδόκιμον νοῦν, de quo Apostolus Rom. i. 28. Sed interim decretum illud reprobationis, secundum quod permittuntur ita indurescere, dependet ex Dei liberrima voluntate, et non ex praevisa illorum finali duritie; quae utique praevisa esse non potuit, nisi hoc permittendi decreto praesupposito.