Bellarmine's meaning: no feeble good without grace, only a capacity that new strength makes able; his answer to Chemnitz
These words of Bellarmine, in which he says that man can do nothing at all of himself in what concerns salvation and piety, show in what sense he ascribes to the sinner who lacks God's grace an imperfect power for spiritual and saving good.
He does not think that without grace a man can achieve something of that kind, if only feebly and imperfectly. He means only that after sin there remains in man a certain power which, once it receives new strength through grace, can move freely toward spiritual good, though before, left to itself, it could do nothing at all about it.
Bellarmine himself makes this point in answering Chemnitz's dilemma: 'Either man has some strength of his own, however slight, or none at all. If he has some, then he can do something without God's grace; if none, then free choice is extinguished.' He replies that man has only a remote power and imperfect strength, and so can do nothing by himself; but if that power is perfected and strength is added, he can achieve a great deal.
Latin
VIII. Porro haec verba Bellarmini, quibus asserit in iis quae salutem & pietatem spectant, hominem nihil omnino ex se facere posse, explicant quo sensu tribuat homini peccatori & gratia Dei destituto potentiam quandam imperfectam ad spirituale & salutare bonum. Nec enim propterea existimat hominem sine gratia in eo genere aliquid praestare quidem posse, verum languide atque imperfecte: sed solum mens ejus est, in homine manere post peccatum potentiam quandam, quae viribus novis per gratiam acceptis, in bonum spirituale libere ferri potest, circa quod ante per se sola nihil omnino agere poterat. Quod observat ipse Bellarminus respondens ad hoc Kemnitii dilemma. Aut habet homo ex se aliquas vires, quamvis exiles; aut nullas omnino. Si habet aliquas, ergo potest aliquid sine Dei gratia. Si nullas; ergo extinctum est liberum arbitrium. Respondet enim hominem habere potentiam tantum remotam & vires imperfectas, & ideo nihil per se posse. Sed si perficiatur ea potentia, & vires addantur, illum posse multa praestare.