Obj. 2:  Further, every separation is opposed to unity.  If therefore sorrow were caused by a craving for unity, no separation would be pleasant:  and this is clearly untrue as regards the separation of whatever is superfluous.

Obj. 3:  Further, for the same reason we desire the conjunction of good and the removal of evil.  But as conjunction regards unity, since it is a kind of union; so separation is contrary to unity.  Therefore the craving for unity should not be reckoned, rather than the craving for separation, as causing sorrow.

On the contrary, Augustine says (De Lib.  Arb. iii, 23), that “from the pain that dumb animals feel, it is quite evident how their souls desire unity, in ruling and quickening their bodies.  For what else is pain but a feeling of impatience of division or corruption?”

I answer that, Forasmuch as the desire or craving for good is reckoned as a cause of sorrow, so must a craving for unity, and love, be accounted as causing sorrow.  Because the good of each thing consists in a certain unity, inasmuch as each thing has, united in itself, the elements of which its perfection consists:  wherefore the Platonists held that one is a principle, just as good is.  Hence everything naturally desires unity, just as it desires goodness:  and therefore, just as love or desire for good is a cause of sorrow, so also is the love or craving for unity.

Reply Obj. 1:  Not every kind of union causes perfect goodness, but only that on which the perfect being of a thing depends.  Hence neither does the desire of any kind of unity cause pain or sorrow, as some have maintained:  whose opinion is refuted by the Philosopher from the fact that repletion is not always pleasant; for instance, when a man has eaten to repletion, he takes no further pleasure in eating; because repletion or union of this kind, is repugnant rather than conducive to perfect being.  Consequently sorrow is caused by the craving, not for any kind of unity, but for that unity in which the perfection of nature consists.

Reply Obj. 2:  Separation can be pleasant, either because it removes something contrary to a thing’s perfection, or because it has some union connected with it, such as union of the sense to its object.

Reply Obj. 3:  Separation from things hurtful and corruptive is desired, in so far as they destroy the unity which is due.  Wherefore the desire for such like separation is not the first cause of sorrow, whereas the craving for unity is. ________________________

FOURTH ARTICLE [I-II, Q. 36, Art. 4]

Whether an Irresistible Power Is a Cause of Sorrow?

Objection 1:  It would seem that a greater power should not be reckoned a cause of sorrow.  For that which is in the power of the agent is not present but future.  But sorrow is for present evil.  Therefore a greater power is not a cause of sorrow.

Obj. 2:  Further, hurt inflicted is the cause of sorrow.  But hurt can be inflicted even by a lesser power.  Therefore a greater power should not be reckoned as a cause of sorrow.