The decree determines the act but leaves the faculty flexible: true in the divided, not the composite sense
It is objected that once God has decreed some act of the human will, the will cannot act otherwise, so its indifference in acting, where freedom lies, is removed. They answer that it cannot both be true that God decreed the will should do something and that the will does not do it or does something else.
Yet God's decree does not prevent the will from keeping the power to act otherwise. The decree determines the act, but leaves the faculty able to turn to the opposite. So when a man does something in keeping with God's decree, it can truly be said that he is able not to do it and to act otherwise. God decreed that he should do this, but should do it in such a way that he remains able to act otherwise.
Thus, granted the divine decree, it is not true in the composite sense that the will can act or not act; but it is true in the divided sense. The opposite act cannot stand together with the divine decree, but the faculty for the opposite act stands with it perfectly well.
Latin
XII. Ad id vero quod objicitur, posito decreto divino circa aliquem actum humanae voluntatis, voluntatem humanam non posse aliter agere, adeoque tolli ejus in agendo indifferentiam, in qua posita est libertas, respondent, non quidem simul consistere ut Deus decreverit voluntatem aliquid agere, istud vero voluntas non agat, aut aliter agat: sed tamen decretum Dei non obstare quominus in voluntate maneat potestas aliter agendi: quoniam decretum Dei actum quidem determinat, sed facultatem relinquit flexibilem ad oppositum. Ac proinde quum homo juxta Dei decretum aliquid agit, vere dici potest illum posse non agere, & aliter agere, quia, videlicet, Deus decrevit quidem ut hoc agat, sed tamen ita agat ut potens maneat aliter agendi: Adeoque, licet in sensu composito verum non sit, posito decreto Divino voluntatem posse agere, vel non agere, verum est tamen in sensu diviso: quia cum decreto Divino non consistit quidem actus oppositus, sed optime tamen consistit facultas ad actum oppositum.