St Thomas Aquinas Summa Theologica, I-II, Questions 22-23
“The sentient appetite is generically one faculty, which is called sensuality;
but it is divided into two powers, which are the species of the sentient appetite, viz.,
– the irascible
– the concupiscible.
To make this clear, one must consider that in natural corruptible things there has to be not only an inclination toward pursuing what is suitable and avoiding what is harmful,
but also an inclination toward resisting the corrupting and contrary things that pose an obstacle to what is suitable and that inflict what is harmful…
“Therefore, since the sentient appetite is an inclination that follows upon sentient apprehension, just as a natural appetite is an inclination that follows upon a natural form, it must be the case that in the sentient part [of the soul] there are two appetitive powers:
(i) one through which the soul is simply inclined to pursue those things that are suitable according to the senses and to avoid those things that are harmful, and this is called the concupiscible power; and
(ii) a second through which the soul resists opposing things that pose obstacles to what is suitable and that inflict harm, and this is called the irascible power.
Hence, the object of the irascible power is said to be the difficult (arduum), because the irascible power tends toward overcoming contraries and winning out over them.
“Moreover, these two inclinations are not reducible to a single principle:
(i) For sometimes the soul, in opposition to the inclination of the concupiscible power, inflicts hardships upon itself in order to fight against contraries in accord with the inclination of the irascible power.
For this reason, the passions of the irascible power likewise seem to be opposed to the passions of the concupiscible power; for in most cases aroused concupiscence diminishes anger, and aroused anger diminishes concupiscence.
(ii) The main point is also clear from the fact that the irascible power is, as it were, a promoter and defender of the concupiscible power when it rises up against obstacles to those suitable things sought by the concupiscible power and fights against the harmful things that the concupiscible power shrinks from.
And for this reason all the passions of the irascible power take their origin from passions of the concupiscible power and terminate in the latter.
For instance, anger arises from an already inflicted pain and, having gained vengeance, it terminates in joy.
It is also for this reason that among animals struggles are over concupiscible things like food and sexual pleasure.”
St. Thomas Aquinas, Summa Theologica, I-II, Question 22: On the subject of the passions of the soul
22,1: There are three senses of the term passio (i.e., being acted upon) common in scholastic metaphysics:
(1) In the most general sense a passion is simply the passive reception of some form, even if no contrary form is lost by the patient in the process (e.g., air receives light without losing any contrary form).
(2) In a less general sense a passion is the passive reception of some form along with the loss of some contrary form; such a passion can be
(2a) for the worse (if what is lost was good for the patient) or
(2b) for the better (if what is lost was bad for the patient).
Passions are in the soul in each of these three ways:
(1) In the broad sense of simple passive reception of a form, every instance of the soul’s passive reception of a form, even in acts of sentient and intellective cognition, can be called a passion.
(2) In the narrower sense of passive reception with a loss, the passions belong to the soul because of bodily transmutations, so that “the passion properly speaking belongs to the soul only per accidens–namely, insofar as the composite is acted upon.” Further, the notion of passion is more properly applied to the soul when the transmutation is
(2a) for the worse than when it is
(2b) for the better, so that “pain (tristitia) is more properly a passion than is joy (laetitia).”
St. Thomas Aquinas, Summa Theologica, I-II, Question 22, Art. 2 brings us a step closer to a full definition of a passion of the soul by focussing on the question of whether it is the apprehensive (cognitive) part of the soul or the appetitive (affective) part that is the subject of the passions of the soul.
The term passion connotes an attraction toward an agent, and it is the appetitive part of the soul, rather than the apprehensive part, that is drawn toward the things that affect the body.
“Passions pertain to defect, since they belong to a thing insofar as it is in potentiality. So in those things which approach the First Perfect Being–viz., God–one finds little potentiality and passion, whereas in other things one finds more. And so, too, in the higher part of the soul–viz., the apprehensive part, there is less of passion [than in the appetitive part].”
Moreover, the appetitive part is active with respect to exterior acts precisely because it is passively ordered to things in themselves as opposed to things as they exist intentionally in the apprehension.
This points to a difference in the corporeal transmutations that lead to apprehension on the one hand and affection on the other. Bodily organs, insofar as they are involved in sentient apprehension, are modified with respect to those intentional properties by virtue of which they are able to play a role in sentient cognition, whereas the bodily changes relevant to sentient appetition are modifications of the natural properties of bodily organs, e.g., their becoming warm or hot, etc.–modifications that are incidental to whatever cognitive roles the bodily organs might have but are essential to their appetitive role. So even though sentient apprehension and sentient appetition both involve acts of corporeal organs, they differ from one another because they are related to different properites of those organs.
So a passion of the soul is (materially) a corporeal change, effected by some object, which (i) is received in a bodily organ with respect to its natural properties [“for example, one says that ‘anger is an inflammation of the blood around the heart'”] and which (ii) is (formally) ordered back toward the object as it exists in itself.
St. Thomas Aquinas, Summa Theologica, I-II, Question 22 Article 3: Passions of the soul, then, are properly found only where there are bodily changes, and so they do not exist in the rational part of the soul or in angels or God. Nonetheless, there are immaterial appetitive acts of will which have effects similar to the effects of the passions, even though they are non-corporeal and hence not themselves passions. For instance, an angel can have joy (gaudium) though not sense pleasure, and higher love (dilectio) though not sense-love.
St. Thomas Aquinas, Summa Theologica, I-II, Question 23: On the differences among the passions
23, articles 1 to 4 : St. Thomas here begins his taxonomy of the eleven basic passions, which takes up the whole of question 23. He cites three principles of division:
A. The first division (art. 1) is into the passions of the concupiscible appetite (object=a good or evil qua simply pleasurable or painful) and the passions of the irascible appetite (object=a good qua difficult to obtain or evil qua difficult to avoid).
B. The second division (art. 2) is into passions that are related directly to goods (either simply or qua difficult to obtain) and passions that are related directly to evils (either simply or qua difficult to avoid).
C. The third division (art. 3), which has to do with the inner nature of the passions, is into
(i) passions that involve inclinations toward or away from objects,
(ii) passions that involve motions toward or away from objects, and
(iii) passions that involve the possession (actual or intentional) of objects.
Given these parameters, plus the added note that anger has no contrary (art. 3), we get the following taxonomy of basic passions of the soul (art. 4):
Passions of the concupiscible appetite, where the object of the concupiscible power in general is sensible good or sensible evil taken absolutely, i.e., the pleasurable or painful as such:
1a. inclination toward a good: amor (love)
1b. inclination away from an evil: odium (hate)
2a. motion to a possible future good: desiderium/concupiscentia (desire)
2b. motion away from a possible future evil: fuga/abominatio (avoidance)
3a. possession of a good: delectatio/gaudium/laetitia (pleasure/joy)
3b. possession of an evil: dolor/tristitia (pain/sadness)
Passions of the irascible appetite, where the object of the irascible appetite in general is sensible good insofar as it is difficult to attain and sensible evil insofar as it is difficult to avoid. These passions all presuppose a concupiscible inclination toward the sensible good in question or away from the sensible evil in question:
1a. inclination toward a difficult future good qua possible to attain: spes (hope)
1b. inclination away from a difficult future good qua impossible to attain: desperatio (despair)
2a. inclination away from a difficult future evil qua impossible to overcome: timor (fear)
2b. inclination toward a difficult future evil qua possible to overcome: audacia (daring)
3. reaction to a present or past evil qua something to be avenged: ira (anger)