3. The will is changed from sin to goodness only by the grace of God (B. III, Chapp. CLVII, CLVIII). But as the souls of the good are admitted to a perfect participation in the divine goodness, so the souls of the damned are totally excluded from grace.
4. As the good, living in the flesh, make God the ultimate end of all their doings and desires, so the wicked set up their rest in some undue end which turns them away from God. But the disembodied spirits of the good will immovably cling to the end which they have set before themselves in this life, namely, God. Therefore the souls of the wicked will immovably cling to the end which they too have chosen for themselves.* As then the will of the good cannot become evil, so the will of the evil cannot become good.
4.92 : That the Souls of the Saints after Death have their Will immutably fixed on Good
4.94 : Of the Immutability of the Will of Souls detained in Purgatory