an act; and in
both respects it is from God. Because every being, whatever the mode
of its being, must be derived from the First Being, as Dionysius
declares (Div. Nom. v). Again every action is caused by something
existing in act, since nothing produces an action save in so far as
it is in act; and every being in act is reduced to the First Act,
viz. God, as to its cause, Who is act by His Essence. Therefore God
is the cause of every action, in so far as it is an action. But sin
denotes a being and an action with a defect: and this defect is from
the created cause, viz. the free-will, as falling away from the order
of the First Agent, viz. God. Consequently this defect is not reduced
to God as its cause, but to the free-will: even as the defect of
limping is reduced to a crooked leg as its cause, but not to the
motive power, which nevertheless causes whatever there is of movement
in the limping. Accordingly God is the cause of the act of sin: and
yet He is not the cause of sin, because He does not cause the act to
have a defect.

Reply Obj. 1: In this passage Augustine calls by the name of "thing,"
that which is a thing simply, viz. substance; for in this sense the
act of sin is not a thing.

Reply Obj. 2: Not only the act, but also the defect, is reduced to
man as its cause, which defect consists in man not being subject to
Whom he ought to be, although he does not intend this principally.
Wherefore man is the cause of the sin: while God is the cause of the
act, in such a way, that nowise is He the cause of the defect
accompanying the act, so that He is not the cause of the sin.

Reply Obj. 3: As stated above (Q. 72, A. 1), acts and habits do not
take their species from the privation itself, wherein consists the
nature of evil, but from some object, to which that privation is
united: and so this defect which consists in not being from God,
belongs to the species of the act consequently, and not as a specific
difference.
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THIRD ARTICLE [I-II, Q. 79, Art. 3]

Whether God Is the Cause of Spiritual Blindness and Hardness of
Heart?

Objection 1: It would seem that God is not the cause of spiritual
blindness and hardness of heart. For Augustine says (Qq. lxxxiii, qu.
3) that God is not the cause of that which makes man worse. Now man
is made worse by spiritual blindness and hardness of heart. Therefore
God is not the cause of spiritual blindness and hardness of heart.

Obj. 2: Further, F