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.

Obj. 3: Further, the interior inclinations of the soul are the causes
of the movements of appetite. But a greater power is something
external. Therefore it should not be reckoned as a cause of sorrow.

_On the contrary,_ Augustine says (De Nat. Boni xx): "Sorrow in the
soul is caused by the will resisting a stronger power: while pain in
the body is caused by sense resisting a stronger body."

_I answer that,_ As stated above (A. 1), a present evil, is cause of
sorrow or pain, by way of object. Therefore that which is the cause
of the evil being present, should be reckoned as causing pain or
sorrow. Now it is evident that it is contrary to the inclination of
the appetite to be united with a present evil: and whatever is
contrary to a thing's inclination does not happen to it save by the
action of something stronger. Wherefore Augustine reckons a greater
power as being the cause of sorrow.

But it must be noted that if the stronger power goes so far as to
transform the contrary inclination into its own inclination there
will be no longer repugnance or violence: thus if a stronger agent,
by its action on a heavy body, deprives it of its downward tendency,
its consequent upward tendency is not violent but natural to it.

According