Oportet in actibus humanis voluntarium esse quia quodcumque agit vel movetur a principio intrinseco, quod habet aliquam notitiam finis, habet in seipso principium sui actus non solum ut agat, sed etiam ut agat propter finem.
There must needs be something voluntary in human acts because whatever acts or is moved by an intrinsic principle, that it has some knowledge of the end, has within itself the principle of its act, so that it not only acts, but acts for an end.
Hoc enim importat nomen voluntarii, quod motus et actus sit a propria inclinatione. Et inde est quod voluntarium dicitur esse, secundum definitionem Aristotelis et Gregorii Nysseni et Damasceni, non solum cuius principium est intra, sed cum additione scientiae. Unde, cum homo maxime cognoscat finem sui operis et moveat seipsum, in eius actibus maxime voluntarium invenitur.
The word "voluntary" implies that their movements and acts are from their own inclination. Hence it is that, according to the definitions of Aristotle, Gregory of Nyssa, and Damascene, the voluntary is defined not only as having "a principle within" the agent, but also as implying "knowledge." Therefore, since man especially knows the end of his work, and moves himself, in his acts especially is the voluntary to be found.
Deus movet hominem ad agendum non solum sicut proponens sensui appetibile, vel sicut immutans corpus, sed etiam sicut movens ipsam voluntatem; quia omnis motus tam voluntatis quam naturae, ab eo procedit sicut a primo movente. Et sicut non est contra rationem naturae quod motus naturae sit a Deo sicut a primo movente (inquantum natura est quoddam instrumentum Dei moventis), ita non est contra rationem actus voluntarii quod sit a Deo (inquantum voluntas a Deo movetur). Est tamen communiter de ratione naturalis et voluntarii motus, quod sint a principio intrinseco.
God moves man to act, not only by proposing the appetible to the senses, or by effecting a change in his body, but also by moving the will itself; because every movement either of the will or of nature, proceeds from God as the First Mover. And just as it is not incompatible with the formal aspect of nature that the natural movement be from God as the First Mover (inasmuch as nature is an instrument of God moving it), so it is not contrary to the formal aspect of a voluntary act, that it proceed from God (inasmuch as the will is moved by God). Nevertheless both natural and voluntary movements have this formal aspect in common, that they should proceed from a principle within the agent.
Damascenus, in II libro, quod "voluntarium est actus qui est operatio rationalis".
Damascene says (De Fide Orth. ii) that "the voluntary is an act consisting in a rational operation."