Unlike the fine deeds of unbelievers
Thesis XI. The good works of believers differ not only from open sins, that is, from actions that are evil in themselves and forbidden by the law. They also differ from the fine deeds of unbelievers that look like virtue and are good and praiseworthy by civic standards.
When unbelievers seem to practise some virtue, such as kindness, justice or self-control, the substance of the act is good, but the act as a whole is simply bad. It does not come from the source all truly good and holy actions must come from, the love of God, and it does not aim at the goal they must aim at, the glory of God.
Believers' works, done by God's grace, aim at God's glory and come from love. So those acts of unbelievers, however impressive they look to human judgment, are not pleasing or acceptable to God, and they do their doers no good at all for eternal salvation. Believers' works are pleasing and acceptable to God, and he rewards them with eternal salvation.
Latin
XI. Neque solum a peccatis manifestis, id est, actionibus per se malis & lege vetitis differunt bona fidelium opera: sed etiam ab ipsis infidelium egregie factis, quae speciem virtutis habent, & civiliter bona ac laudabilia sunt. Etenim in ejusmodi actibus infidelium, quibus virtutem aliquam exercere videntur, puta benignitatis, justitiae & temperantiae, substantia quidem actionis bona est, veruntamen actio simpliciter est mala: quia non procedit ab eo principio a quo manare debent actiones omnes vere bonae & sanctae, scilicet, a Dei amore: neque tendit in finem ad quem spectare debent eaedem actiones, nimirum ad Dei gloriam. Sed fidelium opera per gratiam Dei facta ad gloriam Dei tendunt, & ex charitate procedunt. Ideoque actiones illae infidelium, utut hominum judicio speciosae videantur, Deo gratae & acceptae non sunt: nec quicquam authoribus suis ad salutem aeternam prosunt. Sed fidelium opera Deo grata atque accepta sunt, & aeternae salutis remunerationem ab eo accipiunt.