From the Angelic Doctor...
"We use all things by the act of the will. Hence from a good will, which makes a man use well what he has, man is called good, and from a bad will he is called bad. For a man who has a bad will can use ill even the good he has...Because the fault itself consists in the disordered privation of something used by the will, fault has more of evil in it than pain has."
-- Saint Thomas Aquinas (1225-74)