Brutis animalibus non est electio quia proprie voluntatis est eligere, non autem appetitus sensitivi, qui solus est in brutis animalibus.
Choice is not in irrational animals because choice belongs properly to the will, and not to the sensitive appetite which is all that irrational animals have.
Appetitus sensitivus est determinatus ad unum aliquid particulare secundum ordinem naturae; voluntas autem est quidem, secundum naturae ordinem, determinata ad unum commune, quod est bonum, sed indeterminate se habet respectu particularium bonorum.
The sensitive appetite is determinate to one particular thing, according to the order of nature; whereas the will, although determinate to one thing in general, viz. the good, according to the order of nature, is nevertheless indeterminate in respect of particular goods.
Brutum animal accipit unum prae alio, quia appetitus eius est naturaliter determinatus ad ipsum. Unde statim quando per sensum vel per imaginationem repraesentatur sibi aliquid ad quod naturaliter inclinatur eius appetitus, absque electione in illud solum movetur.
An irrational animal takes one thing in preference to another, because its appetite is naturally determinate to that thing. Wherefore as soon as an animal, whether by its sense or by its imagination, represents to itself something to which its appetite is naturally inclined, it is moved to that alone, without making any choice.
In operibus brutorum animalium apparent quaedam sagacitates, inquantum habent inclinationem naturalem ad quosdam ordinatissimos processus, utpote a summa arte ordinatos. Et propter hoc etiam quaedam animalia dicuntur prudentia vel sagacia, non quod in eis sit aliqua ratio vel electio. Quod ex hoc apparet, quod omnia quae sunt unius naturae, similiter operantur.
In the works of irrational animals we notice certain marks of sagacity, in so far as they have a natural inclination to set about their actions in a most orderly manner through being ordained by the Supreme art. For which reason, too, certain animals are called prudent or sagacious, and not because they reason or exercise any choice about things. This is clear from the fact that all that share in one nature, invariably act in the same way.
Gregorius Nyssenus dicit, quod "pueri et irrationalia voluntarie quidem faciunt, non tamen eligentia".
Gregory of Nyssa [Nemesius, De Nat. Hom. xxxiii.] says that "children and irrational animals act willingly but not from choice."