Synergism. Luther's colleague Philipp Melanchthon taught that the human will can be said to cooperate with the Holy Spirit and the grace of God, although the primary cause of the conversion that is accomplished is the Spirit of God, not the will of man. His teaching on this point is in the tradition of the Semi-Pelagians. 

Geddes MacGregor, Dictionary of Religion and Philosophy, New York: Paragon House, 1989