Dolor, secundum quod est in appetitu sensitivo, propriissime dicitur passio animae, quia omnis motus appetitus sensitivi dicitur passio, ut supra dictum est, et praecipue illi qui in defectum sonant.
Pain, according as it is in the sensitive appetite, is most properly called a passion of the soul, because every movement of the sensitive appetite is called a passion, as stated above (q22, a1,a3), and especially those which tend to some defect.
Dolor dicitur esse corporis, quia causa doloris est in corpore: puta cum patimur aliquod nocivum corpori. Sed motus doloris semper est in anima, nam "corpus non potest dolere nisi dolente anima", ut Augustinus dicit.
We speak of pain as of the body, because the cause of pain is in the body: as when we suffer something hurtful to the body. But the movement of pain is always in the soul; since "the body cannot feel pain unless the soul feel it," as Augustine says (Super Psalm 87:4).
Sicut ad delectationem duo requiruntur (scilicet coniunctio boni, et perceptio huiusmodi coniunctionis), ita etiam ad dolorem duo requiruntur: scilicet coniunctio alicuius mali (quod ea ratione est malum, quia privat aliquod bonum), et perceptio huiusmodi coniunctionis.
Just as two things are requisite for pleasure (namely, conjunction with good and perception of this conjunction), so also two things are requisite for pain: namely, conjunction with some evil (which is evil by the formal aspect that it deprives one of some good), and perception of this conjunction.
Quidquid autem coniungitur, si non habeat, respectu eius cui coniungitur, rationem boni vel mali, non potest causare delectationem vel dolorem. Ex quo patet quod aliquid sub ratione boni vel mali, est obiectum delectationis et doloris. Bonum autem et malum, inquantum huiusmodi, sunt obiecta appetitus. Unde patet quod delectatio et dolor ad appetitum pertinent.
Now whatever is conjoined, if it have not the formal aspect of good or evil in regard to the being to which it is conjoined, cannot cause pleasure or pain. Whence it is evident that something under the formal aspect of good or evil is the object of the pleasure or pain. But good and evil, as such, are objects of the appetite. Consequently it is clear that pleasure and pain belong to the appetite.
Augustinus, XIV de Civ. Dei, ponit dolorem inter passiones animae, inducens illud Virgilii, "hinc metuunt, cupiunt, gaudentque dolentque".
Augustine (De Civ. Dei xiv, 8) reckons pain among the passions of the soul, quoting Virgil: "hence wild desires and grovelling fears/And human laughter, human tears" (Aeneid, vi, 733) [Translation: Conington.]