Ratio passionis magis invenitur in parte appetitiva quam in parte apprehensiva, quia in nomine passionis importatur quod patiens trahatur ad id quod est agentis.
The formal aspect of passion is found more in the appetitive rather than in the apprehensive part, because the word "passion" implies that the patient is drawn to that which belongs to the agent.
Magis autem trahitur anima ad rem per vim appetitivam quam per vim apprehensivam: nam per vim appetitivam anima habet ordinem ad ipsas res, prout in seipsis sunt; unde philosophus dicit, in VI Metaphys., quod "bonum et malum", quae sunt obiecta appetitivae potentiae, "sunt in ipsis rebus".
Now the soul is drawn to a thing by the appetitive power rather than by the apprehensive power: because the soul has, through its appetitive power, an order to things as they are in themselves; hence the Philosopher says (Metaph. vi, 4) that "good and evil," i.e., the objects of the appetitive power, "are in things themselves".
Vis autem apprehensiva non trahitur ad rem, secundum quod in seipsa est, sed cognoscit eam secundum intentionem rei, quam in se habet vel recipit secundum proprium modum. Unde et ibidem dicitur quod "verum et falsum", quae ad cognitionem pertinent, "non sunt in rebus, sed in mente".
On the other hand the apprehensive power is not drawn to a thing, as it is in itself, but knows it according to an "intention" of the thing, which "intention" it has in itself, or receives according to a specific way. Hence we find it stated (Metaph. vi, 4) that "the true and the false," which pertain to knowledge, "are not in things, but in the mind".
Sicut in primo dictum est, dupliciter organum animae potest transmutari. Uno modo, transmutatione spirituali, secundum quod recipit intentionem rei. Et hoc per se invenitur in actu apprehensivae virtutis sensitivae: sicut oculus immutatur a visibili, non ita quod coloretur, sed ita quod recipiat intentionem coloris.
As stated above (in I, q78, a3), the organs of the soul can be changed in two ways. First, by a [formal] spiritual change, according to which the organ receives an "intention" of the object. And this [kind of change] is essential to the act of the sensitive apprehension: thus is the eye [formally] "changed" by the object visible, i.e., not by [materially] being colored, but by [formally] receiving an intention of color.
Est autem alia naturalis transmutatio organi, prout organum transmutatur quantum ad suam naturalem dispositionem; puta quod calefit aut infrigidatur, vel alio simili modo transmutatur. Et huiusmodi transmutatio per accidens se habet ad actum apprehensivae virtutis sensitivae: puta cum oculus fatigatur ex forti intuitu, vel dissolvitur ex vehementia visibilis.
But the organs are receptive of another and natural change, which affects their natural disposition; for instance, when they become hot or cold, or undergo some similar [material] change. And this [second] kind of change is incidental to the act of the sensitive apprehension: for instance, if the eye be wearied through gazing intently at something or be overcome by the intensity of the object.
Sed ad actum appetitus sensitivi per se ordinatur huiusmodi transmutatio: unde in definitione motuum appetitivae partis, materialiter ponitur aliqua naturalis transmutatio organi; sicut dicitur quod "ira est accensio sanguinis circa cor". Unde patet quod ratio passionis magis invenitur in actu sensitivae virtutis appetitivae, quam in actu sensitivae virtutis apprehensivae, licet utraque sit actus organi corporalis.
On the other hand, [this second kind of change] is essential to the act of the sensitive appetite: wherefore the material element in the definitions of the movements of the appetitive part, is the natural change of the organ; for instance, "anger is" said to be "a kindling of the blood about the heart". Hence it is evident that the formal aspect of passion is more consistent with the act of the sensitive appetite, than with that of the sensitive apprehension, although both are actions of a corporeal organ.