In accordance with this manner of speaking, the species of sorrow are reckoned by an application of the notion of sorrow to something foreign to it. This foreign matter may be taken on the part of the cause or the object, or of the effect. For the proper object of sorrow is one’s own evil. Hence sorrow may be concerned for an object foreign to it either through one’s being sorry for an evil that is not one’s own; and thus we have pity which is sorrow for another’s evil, considered, however, as one’s own: or through one’s being sorry for something that is neither evil nor one’s own, but another’s good, considered, however, as one’s own evil: and thus we have envy. The proper effect of sorrow consists in a certain flight of the appetite. Wherefore the foreign element in the effect of sorrow, may be taken so as to affect the first part only, by excluding flight: and thus we have anxiety which weighs on the mind, so as to make escape seem impossible: hence it is also called perplexity. If, however, the mind be weighed down so much, that even the limbs become motionless, which belongs to torpor, then we have the foreign element affecting both, since there is neither flight, nor is the effect in the appetite. And the reason why torpor especially is said to deprive one of speech is because of all the external movements the voice is the best expression of the inward thought and desire, not only in men, but also in other animals, as is stated in Polit. i, 1.
Reply Obj. 1: Pleasure is caused by good, which has only one meaning: and so pleasure is not divided into several species as sorrow is; for the latter is caused by evil, which “happens in many ways,” as Dionysius says (Div. Nom. iv).
Reply Obj. 2: Repentance is for one’s own evil, which is the proper object of sorrow: wherefore it does not belong to these species. Jealousy and indignation are included in envy, as we shall explain later (II-II, Q. 36, A. 2).
Reply Obj. 3: This division is not according to opposite species; but according to the diversity of foreign matter to which the notion of sorrow is applied, as stated above. ________________________