Reply Obj. 2: Pleasure and its contrary pain have the same object, but under contrary aspects: because if the presence of a particular thing be the object of pleasure, the absence of that same thing is the object of sorrow. Now one contrary includes the privation of the other, as stated in Metaph. x, 4: and consequently sorrow in respect of one contrary is, in a way, directed to the same thing under a contrary aspect.
Reply Obj. 3: When many movements arise from one cause, it does not follow that they all regard chiefly that which the cause regards chiefly, but only the first of them. And each of the others regards chiefly that which is suitable to it according to its own nature. ________________________
SECOND ARTICLE [I-II, Q. 36, Art. 2]
Whether Desire Is a Cause of Sorrow?
Objection 1: It would seem that desire is not a cause of pain or sorrow. Because sorrow of itself regards evil, as stated above (A. 1): whereas desire is a movement of the appetite towards good. Now movement towards one contrary is not a cause of movement towards the other contrary. Therefore desire is not a cause of pain.
Obj. 2: Further, pain, according to Damascene (De Fide Orth. ii, 12), is caused by something present; whereas the object of desire is something future. Therefore desire is not a cause of pain.
Obj. 3: Further, that which is pleasant in itself is not a cause of pain. But desire is pleasant in itself, as the Philosopher says (Rhet. i, 11). Therefore desire is not a cause of pain or sorrow.
On the contrary, Augustine says (Enchiridion xxiv): "When ignorance of things necessary to be done, and desire of things hurtful, found their way in: error and pain stole an entrance in their company." But ignorance is the cause of error. Therefore desire is a cause of sorrow.
I answer that, Sorrow is a movement of the animal appetite. Now, as stated above (A. 1), the appetitive movement is likened to the natural appetite; a likeness, that may be assigned to a twofold cause; one, on the part of the end, the other, on the part of the principle of movement. Thus, on the part of the end, the cause of a heavy body's downward movement is the lower place; while the principle of that movement is a natural inclination resulting from gravity.
Now the cause of the appetitive movement, on the part of the end, is the object of that movement. And thus, it has been said above (A. 1) that the cause of pain or sorrow is a present evil. On the other hand, the cause, by way of principle, of that movement, is the inward inclination of the appetite; which inclination regards, first of all, the good, and in consequence, the rejection of a contrary evil. Hence the first principle of this appetitive movement is love, which is the first inclination of the appetite towards the possession of good: while the second principle is hatred, which is the first inclination of the appetite towards the avoidance of evil. But since concupiscence or desire is the first effect of love, which gives rise to the greatest pleasure, as stated above (Q. 32, A. 6); hence it is that Augustine often speaks of desire or concupiscence in the sense of love, as was also stated (Q. 30, A. 2, ad 2): and in this sense he says that desire is the universal cause of sorrow. Sometimes, however, desire taken in its proper sense, is the cause of sorrow. Because whatever hinders a movement from reaching its end is contrary to that movement. Now that which is contrary to the movement of the appetite, is a cause of sorrow. Consequently, desire becomes a cause of sorrow, in so far as we sorrow for the delay of a desired good, or for its entire removal. But it cannot be a universal cause of sorrow: since we sorrow more for the loss of present good, in which we have already taken pleasure, than for the withdrawal of future good which we desire to have.