ughly efficacious powers to our will, who has said
(Ezech. XXXVI, 27): 'I will cause you to walk in my commandments, and to
keep my judgments, and do them.' When He says: 'I will cause you ... to do
them,' what else does He say in fact than (Ezech. XI, 19): 'I will take
away the stony heart out of their flesh,' from which used to rise your
inability to act, and (Ezech. XXXVI, 26): 'I will give you a heart of
flesh,' in order that you may act."(97)

{~GREEK SMALL LETTER BETA~}) The manner in which grace and free-will cooeperate is a profound
philosophical and theological problem. A salutary act derives its
supernatural character from God, its vitality from the human will. How do
these two factors conjointly produce one and the same act? The unity of
the act would be destroyed if God and the free-will of man in each case
performed, either two separate acts, or each half of the same act. To
preserve the unity of a supernatural act two conditions are required: (1)
the divine power of grace must be transformed into the vital strength of
the will and (2) the created will, which by its own power can perform at
most a naturally good act, must be equipped with the supernatural power of
grace. These conditions are met (a) by the supernatural elevation of the
will (_elevatio externa_), and (b) by the supernatural concurrence of God
(_concursus supernaturalis ad actum secundum_). The supernatural elevation
of the will is accomplished in this wise: God, by employing the
illuminating and strengthening grace, works on the _potentia
oboedientialis_, and thus raises the will above its purely natural powers
and constitutes it a supernatural faculty _in actu primo_ for the free
performance of a salutary act. The divine concursus supervenes to enable
the will to perform the _actus secundus_ or salutary act proper. This
special divine concurrence, in contradistinction to the natural concursus
whereby God supports the created universe,(98) is a strictly supernatural
and gratuitous gift. Consequently, God and the human will jointly perform
one and the same salutary act--God as the principal, the will as the
instrumental cause.(99)

6. EFFICACIOUS GRACE AND MERELY SUFFICIENT GRACE.--By efficacious grace
(_gratia efficax_) we understand that divine assistance which with
infallible certainty includes the free salutary act. Whether the certainty
of its operation results from the physical nature of this particular
grace, or from God's infallible f