Estius and Alvarez: being able to will differs from actually willing; the decree is needed only for the act
Much of the same kind can be read in William Estius in the places cited above, and in Diego Alvarez, summary on the helps of grace, book 2, chapter 6. There Alvarez answers the objections against a predetermination of the will that comes from God's external decree.
He raises this objection against himself. On his view, man can will only what God by an efficacious decree wills him to will, and can perform only acts God has predetermined. So we do not will freely what we will, but by absolute necessity, since we cannot do otherwise if God wills that we do it.
By the same reasoning, the acts commanded of us are not freely left undone. For if God's having predetermined our will to an act is required for us to do it, we cannot do it unless God by his absolute and efficacious decree has predetermined that we shall do it.
He answers that being able to run is one thing and actually running another. In the same way, being able to will or to produce some particular act is one thing, and actually producing it is another. For a man truly to be able to will an object, it is not required that an absolute and efficacious decree should have preceded in God from eternity, predetermining his free choice to will that object. That is required only for him actually to will it.
So from the absence of such a decree in God it does not follow that, absolutely speaking, the man cannot will the object; it follows only that he does not in fact will it. Nor does it follow that, if God has predetermined me to will this particular thing, it is not in my power, absolutely speaking, to will something else. Granted God's efficacious will, however, it is impossible in the composite sense that I should will another object.
Latin
XIV. His similia multa legere est apud Gulielmum Estium locis ante citatis & apud Didacum Alvarez in summa de Auxiliis libro secundo capite sexto, ubi dissolvit objectiones contra praedeterminationem voluntatis ex decreto Dei extrinseco provenientem. Ad illud enim quod sibi objicit ex ejus sententia sequi hominem non posse velle, nisi id quod Deus efficaci decreto vult eum velle: nec posse operari nisi actus praedeterminatos a Deo; adeoque nos non libere velle id quod volumus, sed ex necessitate absoluta, quia non possumus aliter facere, si Deus vult ut faciamus illud, Et eadem ratione non libere omitti a nobis eos actus qui sunt in praecepto: Quia si necessarium est ad hoc ut talem actum faciamus, ut Deus praedeterminaverit voluntatem nostram ad eundem actum, illum facere non possumus, si Deus suo decreto absoluto & efficaci non praedeterminavit actum illum fieri a nobis. Respondet, quod sicut aliud est posse currere, aliud vero actu currere; ita aliud est posse velle, vel producere actum aliquem in particulari; aliud autem de facto illum producere: ut ergo homo vere possit velle aliquod objectum, non requiri quod ex aeternitate praecesserit in Deo absolutum & efficax decretum praedeterminans ejus liberum arbitrium ad volendum idem objectum; quamvis id requiratur ut illud actu velit. Unde ex hoc quod in Deo non fuerit hujusmodi decretum, non sequi quod homo non possit velle tale objectum absolute loquendo: sed solum sequi quod de facto non velit illud. Nec etiam sequi quod, si Deus praedeterminavit me ad volendum hoc in particulari, non sit, absolute loquendo, in mea potestate aliud velle; quamvis ex suppositione divinae voluntatis efficacis, impossibile sit in sensu composito quod velim aliud objectum.