(CG 3/157). That he who falls from Grace by Sin may be recovered again by... (Book 3. God, the End of Creatures) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

BY mortal sin man is turned away from his last end. And to that last end he is set on his way only by grace.

2. Offence is removed only by love. But by mortal sin man quarrels with God: for it is said that God 'hates' sinners, inasmuch as He is minded to deprive them of the last end, which He has in preparation for them who love Him. Man then cannot rise from sin except by grace, whereby friendship is established between God and man.

Hence it is said: It is I who blot out your iniquities for my own sake (Isai. xliii, 25).

Hereby is refuted the error of the Pelagians, who said that man can rise from sin by free will.