Semi-Pelagianism is a weaker form of Pelagianism (a heresy derived from Pelagius who lived in the 5th century A.D. and was a teacher in Rome). Semi-Pelagianism (advocated by Cassian at Marseilles, 5th Century) did not deny original sin and its effects upon the human soul and will; but, it taught that God and man cooperate to achieve man’s salvation. This cooperation is not by human effort as in keeping the law but rather in the ability of a person to make a free will choice. The semi-Pelagian teaches that man can make the first move toward God by seeking God out of his own free will, and that man can cooperate with God’s grace even to the keeping of his faith through human effort. This would mean that God responds to the initial effort of person, and that God’s grace is not absolutely necessary to maintain faith.
The problem is that this is no longer grace. Grace is the completely unmerited and freely given favor of God upon the sinner; but, if man is the one who first seeks God, then God is responding to the good effort of seeking him. This would mean that God is offering a proper response to the initial effort of man. This is not grace but what is due the person who chooses to believe in God apart from God’s initial effort.
Semi-Pelagianism says the sinner has the ability to initiate belief in God.
Semi-Pelagianism says God’s grace is a response to man’s initial effort.
Semi-Pelagianism denies predestination.
Semi-Pelagianism was condemned at the Council of Orange in 529.
http://carm.org/semi-pelagianism
That is clearly a heresy. Man cannot cooperate with grace:
by grace you are saved through faith, and that not of yourselves, for it is the gift of God; Not of works, that no man may glory (Eph. 2:8-9)Grace is not of works. Man is saved by grace alone.