Hence rational agents are masters of their actions, unlike things moved only by sense
This is where they locate freedom of choice. Those who act on reason's judgement know their end, set it before themselves, and direct and fit their actions to it, so that in a sense they are masters of what they do.
Lifeless things and animals that are led by sense alone, by contrast, do not know their end. So they do not direct themselves to it but only move toward it like slaves, who carry out orders without knowing why they are given or what they are for. They do not so much act for an end as get moved toward an end by a higher agent.
Besides, the sense and appetite of animals are tied to material things. Human will follows the lead of mind and reason, whose objects are not only things of sense but things of the intellect, not only present things but future ones. It ranges over every kind, mode and degree of good and is shut in, so to speak, by no limits. From this comes the great variety in what men desire and choose, and also in their outward actions.
Latin
X. Qua in re libertatem arbitrii constituunt. Idque quoniam illi qui ex judicio rationis agunt finis notitiam habent, eumque sibi praestituunt, & ad eum actiones suas dirigunt atque accommodant: & ita sunt quodammodo actionum suarum Domini. Cum contra res inanimae, & animalia bruta quae solo sensu ducuntur, finem suum non cognoscant; ideoque ad eum seipsa non referant, sed duntaxat ad illum tendant instar mancipiorum, imperata quidem facientium, cur vero imperentur, aut quorsum ignorantium. Neque tam propter finem agunt, quam ad finem ab agente superiore aguntur. Adde quod brutorum sensus & appetitus rebus materialibus astrictus est; hominum vero voluntas, cum sequatur ductum mentis & rationis, quae pro objecto habet non tantum sensibilia, sed etiam intelligibilia, non solum praesentia, sed etiam futura, versatur circa omnia bonorum genera, modos atque gradus, nec ullis, ut sic dicam, limitibus includitur: Unde nascitur maxima appetitionum electionumque necnon actionum externarum varietas.