Freedom before grace is bound, like sight in the dark until the object appears
To show how man before grace has free choice even in spiritual things, though before grace he cannot do good, he says that in that state man's choice is indeed free in that respect, but its freedom is, as it were, bound and hindered. It is untied and released when the proximate power to act is given to it by God's prevenient grace.
He illustrates this: 'We find something like it in the power of sight. When the sensible image is absent, a man has the power and freedom to see, for that image is not the cause of the freedom or of the power of seeing. Yet the power is remote and the freedom bound until the image is received, the power is completed, and it can go out into act.'
Latin
IX. Ut ostendat autem quomodo homo ante gratiam arbitrium liberum habeat, etiam in spiritualibus, cum tamen ante gratiam bonum facere non possit; dicit in eo statu arbitrium hominis liberum quidem eo respectu esse: sed tamen ejus libertatem esse quasi ligatam atque impeditam: solvi autem & expediri, quum potentia proxima ad operandum per Dei gratiam praevenientem ei confertur. Atque ut eam rem illustret, Simile, inquit, aliquid experimur in potentia videndi: nam absente specie sensibili, habet homo potentiam & libertatem videndi: non enim ea species causa est libertatis, aut potentiae videndi; sed tamen potentia remota est, & libertas ligata, donec accepta specie potentia perficiatur, & in actum prodire possit.