1 Objection 1: It would seem that the sensitive appetite is not divided into the irascible and concupiscible as distinct powers. For the same power of the soul regards both sides of a contrariety, as sight regards both black and white, according to the Philosopher De Anima ii, 11). But suitable and harmful are contraries. Since, then, the concupiscible power regards what is suitable, while the irascible is concerned with what is harmful, it seems that irascible and concupiscible are the same power in the soul.
1 Ad secundum sic proceditur. Videtur quod appetitus sensitivus non distinguatur in irascibilem et concupiscibilem, sicut in potentias diversas. Eadem enim potentia animae est unius contrarietatis, ut visus albi et nigri, ut dicitur in II de anima. Sed conveniens et nocivum sunt contraria. Cum ergo concupiscibilis respiciat conveniens, irascibilis vero nocivum, videtur quod eadem potentia animae sit irascibilis et concupiscibilis.
2 Objection 2: Further, the sensitive appetite regards only what is suitable according to the senses. But such is the object of the concupiscible power. Therefore there is no sensitive appetite differing from the concupiscible.
2 Praeterea, appetitus sensitivus non est nisi convenientium secundum sensum. Sed conveniens secundum sensum est obiectum concupiscibilis. Ergo nullus appetitus sensitivus est a concupiscibili differens.
3 Objection 3: Further, hatred is in the irascible part: for Jerome says on Mt. 13, 33: We ought to have the hatred of vice in the irascible power. But hatred is contrary to love, and is in the concupiscible part. Therefore the concupiscible and irascible are the same powers.
3 Praeterea, odium est in irascibili, dicit enim Hieronymus, super Matth., possideamus in irascibili odium vitiorum. Sed odium, cum contrarietur amori, est in concupiscibili. Ergo eadem vis est concupiscibilis et irascibilis.
4 On the contrary, Gregory of Nyssa Nemesius, De Natura Hominis) and Damascene De Fide Orth. ii, 12) assign two parts to the sensitive appetite, the irascible and the concupiscible.
4 Sed contra est quod Gregorius Nyssenus et Damascenus ponunt duas vires, irascibilem et concupiscibilem, partes appetitus sensitivi.
5 I answer that, The sensitive appetite is one generic power, and is called sensuality; but it is divided into two powers, which are species of the sensitive appetite, the irascible and the concupiscible. In order to make this clear, we must observe that in natural corruptible things there is needed an inclination not only to the acquisition of what is suitable and to the avoiding of what is harmful, but also to resistance against corruptive and contrary agencies which are a hindrance to the acquisition of what is suitable, and are productive of harm.
For example, fire has a natural inclination, not only to rise from a lower position, which is unsuitable to it, towards a higher position which is suitable, but also to resist whatever destroys or hinders its action. Therefore, since the sensitive appetite is an inclination following sensitive apprehension, as natural appetite is an inclination following the natural form, there must needs be in the sensitive part two appetitive powers, one through which the soul is simply inclined to seek what is suitable, according to the senses, and to fly from what is hurtful, and this is called the concupiscible: and another, whereby an animal resists these attacks that hinder what is suitable, and inflict harm, and this is called the irascible.
Whence we say that its object is something arduous, because its tendency is to overcome and rise above obstacles. Now these two are not to be reduced to one principle: for sometimes the soul busies itself with unpleasant things, against the inclination of the concupiscible appetite, in order that, following the impulse of the irascible appetite, it may fight against obstacles. Wherefore also the passions of the irascible appetite counteract the passions of the concupiscible appetite: since the concupiscence, on being aroused, diminishes anger; and anger being roused, diminishes concupiscence in many cases.
This is clear also from the fact that the irascible is, as it were, the champion and defender of the concupiscible when it rises up against what hinders the acquisition of the suitable things which the concupiscible desires, or against what inflicts harm, from which the concupiscible flies. And for this reason all the passions of the irascible appetite rise from the passions of the concupiscible appetite and terminate in them; for instance, anger rises from sadness, and having wrought vengeance, terminates in joy.
For this reason also the quarrels of animals are about things concupiscible, namely, food and sex, as the Philosopher says.
5 Respondeo dicendum quod appetitus sensitivus est una vis in genere, quae sensualitas dicitur; sed dividitur in duas potentias, quae sunt species appetitus sensitivi, scilicet in irascibilem et concupiscibilem. Ad cuius evidentiam, considerari oportet quod in rebus naturalibus corruptibilibus, non solum oportet esse inclinationem ad consequendum convenientia et refugiendum nociva; sed etiam ad resistendum corrumpentibus et contrariis, quae convenientibus impedimentum praebent et ingerunt nocumenta. Sicut ignis habet naturalem inclinationem non solum ut recedat ab inferiori loco, qui sibi non convenit, et tendat in locum superiorem sibi convenientem; sed etiam quod resistat corrumpentibus et impedientibus.
Quia igitur appetitus sensitivus est inclinatio consequens apprehensionem sensitivam, sicut appetitus naturalis est inclinatio consequens formam naturalem; necesse est quod in parte sensitiva sint duae appetitivae potentiae. Una, per quam anima simpliciter inclinatur ad prosequendum ea quae sunt convenientia secundum sensum, et ad refugiendum nociva, et haec dicitur concupiscibilis. Alia vero, per quam animal resistit impugnantibus, quae convenientia impugnant et nocumenta inferunt, et haec vis vocatur irascibilis. Unde dicitur quod eius obiectum est arduum, quia scilicet tendit ad hoc quod superet contraria, et superemineat eis.
Hae autem duae inclinationes non reducuntur in unum principium, quia interdum anima tristibus se ingerit, contra inclinationem concupiscibilis, ut secundum inclinationem irascibilis impugnet contraria. Unde etiam passiones irascibilis repugnare videntur passionibus concupiscibilis, nam concupiscentia accensa minuit iram, et ira accensa minuit concupiscentiam, ut in pluribus. Patet etiam ex hoc, quod irascibilis est quasi propugnatrix et defensatrix concupiscibilis, dum insurgit contra ea quae impediunt convenientia, quae concupiscibilis appetit, et ingerunt nociva, quae concupiscibilis refugit. Et propter hoc, omnes passiones irascibilis incipiunt a passionibus concupiscibilis, et in eas terminantur; sicut ira nascitur ex illata tristitia, et vindictam inferens, in laetitiam terminatur. Propter hoc etiam pugnae animalium sunt de concupiscibilibus, scilicet de cibis et venereis, ut dicitur in VIII de animalibus.
6 Reply to Objection 1: The concupiscible power regards both what is suitable and what is unsuitable. But the object of the irascible power is to resist the onslaught of the unsuitable.
6 Ad primum ergo dicendum quod vis concupiscibilis est et convenientis et inconvenientis. Sed irascibilis est ad resistendum inconvenienti quod impugnat.
7 Reply to Objection 2: As in the apprehensive powers of the sensitive part there is an estimative power, which perceives those things which do not impress the senses, as we have said above Question 78, Article 2); so also in the sensitive appetite there is a certain appetitive power which regards something as suitable, not because it pleases the senses, but because it is useful to the animal for self-defense: and this is the irascible power.
7 Ad secundum dicendum quod, sicut in apprehensivis virtutibus in parte sensitiva est aliqua vis aestimativa, scilicet quae est perceptiva eorum quae sensum non immutant, ut supra dictum est; ita etiam in appetitu sensitivo est aliqua vis appetens aliquid quod non est conveniens secundum delectationem sensus, sed secundum quod est utile animali ad suam defensionem. Et haec est vis irascibilis.
8 Reply to Objection 3: Hatred belongs simply to the concupiscible appetite: but by reason of the strife which arises from hatred, it may belong to the irascible appetite.
8 Ad tertium dicendum quod odium simpliciter pertinet ad concupiscibilem; sed ratione impugnationis quae ex odio causatur, potest ad irascibilem pertinere.