Actus appetitus sensitivi subiacet imperio rationis quia apprehensio imaginationis, cum sit particularis, regulatur ab apprehensione rationis, quae est universalis, sicut virtus activa particularis a virtute activa universali.
The act of the sensitive appetite is subject to the command of formal aspect because the apprehension of the imagination, being a particular apprehension, is regulated by the apprehension of formal aspect, which is universal; just as a particular active power is regulated by a universal active power.
Qualitas autem et dispositio corporis non subiacet imperio rationis. Et ideo ex hac parte, impeditur quin motus sensitivi appetitus totaliter subdatur imperio rationis.
On the other hand, condition or disposition of the body is not subject to the command of formal aspect; and consequently in this respect, the movement of the sensitive appetite is hindered from being wholly subject to the command of formal aspect.
Contingit etiam quandoque quod motus appetitus sensitivi subito concitatur ad apprehensionem imaginationis vel sensus. Et tunc ille motus est praeter imperium rationis, quamvis potuisset impediri a ratione, si praevidisset. Unde philosophus dicit, in I Polit., quod ratio praeest irascibili et concupiscibili non principatu despotico, qui est domini ad servum; sed principatu politico aut regali, qui est ad liberos, qui non totaliter subduntur imperio.
Moreover it happens sometimes that the movement of the sensitive appetite is aroused suddenly in consequence of an apprehension of the imagination or of sense. And then such movement occurs without the command of formal aspect—although formal aspect could have prevented it, had it foreseen. Hence the Philosopher says (Polit. i, 2) that formal aspect governs the irascible and concupiscible not by a "despotic supremacy," which is that of a master over his slave; but by a "politic and royal supremacy," whereby the free are governed, who are not wholly subject to command.
Hoc quod homo vult non concupiscere, et tamen concupiscit, contingit ex dispositione corporis, per quam impeditur appetitus sensitivus ne totaliter sequatur imperium rationis. Unde et apostolus ibidem subdit, video aliam legem in membris meis, repugnantem legi mentis meae. Hoc etiam contingit propter subitum motum concupiscentiae, ut dictum est.
That man lusts, although he wills not to lust, is due to a disposition of the body, whereby the sensitive appetite is hindered from perfect compliance with the command of formal aspect. Hence the Apostle adds (Romans 7:15): "I see another law in my members, fighting against the law of my mind." This may also happen through a sudden movement of concupiscence, as stated above.