Bonitas et malitia voluntatis non dependet ex circumstantiis, sed ex solo obiecto, quia bonitas voluntatis ex solo uno illo dependet, quod per se facit bonitatem in actu; scilicet ex obiecto, et non ex circumstantiis (quae sunt quaedam accidentia actus).
The goodness and badness of the will depend, not on the circumstances, but on the object alone, because the goodness of the will's act depends on that one thing alone, which essentially causes goodness in the act; and that one thing is the object, and not the circumstances (which are accidents, as it were, of the act).
Illud autem unum quod est principium in quolibet genere, non est per accidens, sed per se, quia omne quod est per accidens, reducitur ad id quod est per se, sicut ad principium.
That one thing which is the principle in each genus, is not something accidental to that genus, but something essential thereto, because whatever is accidental is reduced to something essential, as to its principle.
Principium autem bonitatis et malitiae humanorum actuum est ex actu voluntatis.
Now the principle of the goodness and malice of human actions is taken from the act of the will.
Finis est obiectum voluntatis, non autem aliarum virium. Unde quantum ad actum voluntatis, non differt bonitas quae est ex obiecto, a bonitate quae est ex fine, sicut in actibus aliarum virium; nisi forte per accidens, prout finis dependet ex fine, et voluntas ex voluntate.
The end is the object of the will, but not of the other powers. Hence, in regard to the act of the will, the goodness derived from the object, does not differ from that which is derived from the end, as they differ in the acts of the other powers; except perhaps accidentally, insofar as one end depends on another, and one act of the will on another.
Supposito quod voluntas sit boni, nulla circumstantia potest eam facere malam.
Given that the act of the will is fixed on some good, no circumstances can make that act bad.