"There Augustine first teaches: the human will does not obtain grace by freedom, but obtains freedom by grace; when the feeling of delight has been imparted through the same grace, the human will is formed to endure; it is strengthened with unconquerable fortitude; controlled by grace; it never will perish, but, if grace forsake it, it will straight way fall; by the Lord's free mercy it is converted to good, and once converted it perseveres in good; the direction of the human will toward good, and after direction its continuation in good, depending solely upon God's will, not upon any merit of man.
Thus there is left to man such free will, if we please so to call it, as he elsewhere describes: that except through grace the will can neither be converted to God nor abide in God; and whether it can do it is able to do only through grace."

--John Calvin